AVIONICS, INSTRUMENTS and ELECTRICAL
One thing to remember is that the Safari is flown from the left seat. This means that if one has to reach for a radio, transponder, instrument, etc. the right hand must come off the cyclic. I have heard of both the technique of letting go of the collective and holding the cyclic with the left hand and also of holding the cyclic with your legs. Time will tell which is most effective for me, but in the meantime, I am choosing to try minimize the reaching for avionics, etc. There's a lot of classified airspace around here and I prefer to keep my hands on the stick, especially since some of this switching would already be at a high workload time such as arrival or departure.
My key (no pun intended) requirements were for remote
frequency select and frequency flip-flop with preference for a
large read-out. My thoughts were that I would go with a
mainstream rack style mount that could get easily repaired or
replaced and that has a large enough customer base that it's not
going to have teething pains. The one negative to this style is
that they are quite deep for mounting. I know that in the past
CHR has recommended the use of 2-1/4" radios and
transponders, but I'm not sure I agree with this. A pair of the 2-1/4"
units is slightly smaller (2.4" H x ~ 5" W versus 3"
H x 6.3" W) but:
- They're significantly more expensive
- They have less remote capabilities for stick-mounted functions
- I don't find them as convenient to use, especially when one has to change hands on the cyclic to do so
- They're not as easily upgraded
- There's fewer support centers
- The various reports of problems that I've heard about.
I ended up getting an ICOM
IC-A200 which is reasonably priced, widely available and
built by a company that has specialized in radios for a long time.
It also has a little more output power (7 W carrier) than some of
the other radios I looked at. Although it is advertised as having
an intercom system, this feature requires a DPDT switch for the
transmit/intercom function. This could be wired into the CHR
supplied cyclic grip trigger switch as either a hot mike or PTT
intercom, but not into some of the military style grips unless
one uses an external relay. I have
heard a rumor that this is the same radio internally as a Bendix-King
KY 97A. When one looks at the various features, they are
basically similar and the wiring pinout appears to be exactly the
N.B. The ICOM wiring diagram shows the connector from the FRONT side and not the side that you'd be inserting wires from.
ICOM has released a new radio (A210) and the preliminary data that I've seen would indicate that it might be highly desireable. It has a built-in VOX intercom, a different display, one button 121.5 callup and a dual frequency monitor. It also appears that it can take frequency inputs from a GPS unit ... basically the same features as the Garmin SL40 which unfortunately does not offer remote pushbutton flip-flop and frequency recall inputs. I've now had a chance to look at the first versions of both the A210 installation manual and also the user's manual. While I think this is a great radio, there are a few shortcomings that I've noticed upon a quick review:
If I were to install this radio in a helicopter, I would use the Molex connector configuration. While this means that one can't use the GPS input to obtain frequencies, it probably isn't much of a limitation since using that kind of a feature requires extra attention and fiddling which probably isn't appropriate. Perhaps ICOM or a third party will release a new connection system that allows access to all the features. At the end of the day, the primary advantage over the A200 would be the built-in VOX intercom (no feedback on it's effectiveness yet), the dual frequency monitor and the emergency channel button (probably not enough time to push it in the case of a real emergency). The price difference between the A200 and A210 appears to be about the same as a good quality intercom.
Update: There is a serious shortcoming in the A210 ... the dualwatch feature was implemented in such a way that if there is activity on the standby frequency then it does not check / monitor the active frequency. The worst case scenario for this would be if one were to dial ATIS on the standby frequency in flight, there would be no monitoring of the primary frequency. It is my understanding that there may be a firmware modification for this but I'd advise checking this out before using this function or purchasing this radio.
If I were to go with a round "instrument style", I would seriously consider the Becker unit but first I would have to verify the remote capabilities. After looking at the wiring diagrams, it would appear that the Becker unit does not directly support remote functions, but possibly might with an external RS232 box. Also, it's not totally clear in the documentation that I've read, but it would appear that the intercom function is of the hot mike variety.
The other unit that appears very interesting is
which has features such as an
integrated VOX intercom, Dual Watch and is very compact. This
unit is now shipping and I've only seen one
independent field report which was very favourable. The one thing
that appears unusual in the wiring is that in order to use the
remote memory channel select and frequency flip-flop, this is
wired into the copilot PTT switch and set in a configuration menu.
Thus it would appear that the copilot cannot actually transmit on
the radio when using the remote feature. Normally this would not
be a problem, but sometimes it is convenient to have the copilot
perform ATC communication, especially during training or
operations at an unfamiliar airport.
Update: XCOM has now released a Remote Module to address the problem of separate switches for memory channel select and frequency flip-flop. I believe this module is a required addition in a helicopter that is flown from the left seat.
I am aware that the Microair M760 is a fairly popular radio which is of the 2-1/4" round style and has hot mike intercom capability. I did briefly consider it, but there were several factors that I decided were not to my liking:
- Lower output power ( 4 watts carrier output )
- Having to choose remote flip-flop or remote memory with immediate switching (i.e. mode)
- The number of units that I'd heard of that had to be returned to Australia for service. Perhaps this was just the early batches and has now been sorted out.
- Reports I'd heard about very slow servicing in Australia
- Price is higher than the ICOM unit I selected
While it doesn't sound reasonable at first, it is possible that one may end up with two radios if they were to install a COM transceiver and then later install a GPS/COM unit. On first glance this would appear to require an audio panel to handle the switching, but its my understanding that one can simply use a 3PDT or 4PDT (to include ground) switch between the intercom and the two radios. One negative of this KISS approach is that it does not normally allow the monitoring of the secondary radio, but I'm still trying to find out more details on the auxiliary audio inputs that some of the transceivers have as I believe this can be used for monitoring. I've also been considering the use of a remote relay switch such as the Northern Airborne (NAT) RS08. This could be wired in such a way as to provide a remote COM1/COM2 selector and indicator that is easily controlled by a switch on the cyclic.
Update: Since I do have two COMs, I had to make a decision how to wire them. While it would be nice to have a switching intercom such as the DC-COM500 or the PS Engineering PMA4000, I'm taking the simpler approach. My choice was to either use a remotely switched relay bank or a simple toggle switch. For now I'm taking the simplest route and installing a 4PDT locking toggle switch which will control the COM1/COM2 selection. The locking feature will prevent the accidental bumping of the switch and disabling of communications. Since I'll probably only ever be using the GPS/COM as a backup radio, the IC-A200 will be the primary radio. Since it does allow for three external audio inputs, I'll be using one of these to monitor the GPS/COM, but with a toggle switch placed in the circuit to enable/disable this feature. This will probably only be used to monitor 121.5 MHz, but there are a few fringe areas where it would be nice to have the main radio on the unpublished local frequency while still monitoring 126.7 MHz.
Transponder and Antenna
Since I couldn't figure out how to conveniently interface to a remotely selectable transponder, I purchased a Garmin GTX-327. One of the big issues here was the easy to use push-button code select that doesn't actually change the code until it's completely entered vs. multiple knobs that instantly change the code. Also, the all solid-state design, altitude readout for confirmation, remote ident and standby etc. were very likeable features. I will be mounting a "squat" micro-switch on the collective, which then lets this unit record flight time (i.e. up-collective time) via a built-in feature. This micro-switch will also drive another Hobbs to record total flight time vs. total engine time.
The GTX-327 is probably on the high end of what most builders will need or want in a transponder. It does have a lot of nice features, but the purchase decision is also influenced by the location where most flying is to take place. If one is normally only flying in non-controlled airspace then it is probably overkill but in my case I'll probably be spending a lot of time in and around Class C and D airpsace. I got an excellent deal on this unit from a Canadian dealer and that definitely tipped the scale.
With the advent of the Garmin GTX-330, there are a lot of upgrades being done with the effect that used GTX-327's with low time are available from dealers and on eBay. I found a dealer that offered new ones for ~$100 more than the eBay prices so I elected to go with the new one with full warranty and a known history.
Another transponder I had considered was the Bendix/King KT 76C. It is also a pushbutton style but it's a couple of inches deeper and I didn't have the installation documentation. Their list price seems to be a bit higher than the GTX-327, but I have seen them come up on eBay occasionally for a much better price and actually less than the GTX-327. I'm led to believe that some Europeans will be forced to upgrade to Mode S in 2005. If that truly is the case, then I'd expect that there will be even more used transponders appearing in places like eBay.
I had looked at the 2-1/4" round style transponders but did not seriously consider them. While I have no factual basis for this, my concern was for the usability of the small input knobs and displays, especially for adjustment in flight while wearing NOMEX® gloves. I am aware of units from Becker and from Microair but both are considerably more expensive than standard rack-mount units which offer more convenient features. I am also aware that have been problems with the Microair units and any of the Rev. 6 or earlier units will probably have to go to a service center for repair.
One off-the-wall mounting idea I had was to mount the transponder somewhere on/in the left side interior panel with the idea that one could easily use the left hand to enter a new code. Upon reflection, I saw how this could be done but I also realized that this puts the transponder well out of the normal scan window. Interestingly enough, I'm not the only one who has had this idea for a mounting location and there is a picture here of an implementation of this in a Rotorway.
Another idea I pursued was to use a transponder with a remote code entry system. The Garmin SL70R was one of the only ones I found that had this feature and also the required documentation. Unfortunately it would require designing and building the display and remote entry system and even though I feel comfortable doing this, it was just one too many projects for me. This unit is now listed as "discontinued" by Garmin after the merging of their product lines, although it does appear to still be supported. The Garmin GTX 32 appears to be a new product that would also support this remote approach, but I haven't seen any detailed documentation and it carries a 25% premium over the GTX 327. I believe the Becker ATC 4401 unit also has this remote capability but I couldn't find any public documentation on it. Even though I'm surrounded by a Class C and a Class D airport, this is something that is possibly only changed a couple of times per flight, especially since the local ATC normally lets one "keep the code" if they're returning.
I got an AV-22 antenna; a little more expensive than the TED ($32 vs. $20), but RA Miller has been around for awhile and publishes full specifications and it's STC'd. Now that I've had a little more time to think about alternatives, I'd have no problems installing one of the small blade style DME/TPX antennas. They're more expensive and a few ounces heavier but they have a larger mounting area making them less likely to cause flexing or to be broken off if something impacts them. Note that there is now a homebuilder alternative to the blade antenna at a reasonable price. Delta Pop Aviation makes these and I've read good things about them from various RV owners.
Update: I ended up including the AV-22 in a
package to someone else. As a result, I'm actually going to use a
Dorne & Margolin DM NI
70-2 blade style antenna that I had acquired.
Update 2: I've decided to go back to an AV-22 antenna. The basic reason is that the blade antenna blocks my paint scheme ... how about that for practical reasoning? The blade antenna ended up on a Lancair IV-P turbo-prop and the owner is very happy with it.
When one first thinks about the requirement for a transponder, it is not obvious that one also requires an altitude encoder in order for the transponder to transmit the Mode C altitude information. In essence, an encoder uses the static line as input to measure air pressure and its output is an encoded digital signal to the transponder. The transmitted altitude is not corrected for ambient temperature or pressure as this is performed by the ATC units receiving the signal. While some expensive altimeters have a built-in encoder, the altimeter supplied by CHR in the instrument package does not have this feature and a separate encoder will probably be required when installing a transponder. While I am planning on eventually adding a Dynon EFIS-D10A which has a built-in encoder, I chose to go with a separate stand-alone encoder both for redundancy and to allow for a deferred purchase / installation of the EFIS unit.
I bought a Trans Cal SSD120-30A.
I had heard some bad things about service on the Ameri-King units and one
subtle thing about the AK350 and the ACK A30 is that they can
take up to 6 minutes to "warm-up" whereas the Trans Cal
only has a delay below 20° C, one minute at 0° C, etc. We'll
see if it was a good choice and whether I later kick myself for
not paying a little more up-front and getting the version with RS-232
output to conveniently drive a GPS or some other unit.
Update: Actually it would have been very convenient and easier to wire if I'd bought the version that has RS-232 outputs. Instead of having to wire 10 connections that each go to two destinations (transponder and GPS), the RS-232 version has one (or two) wire(s) going to each of these devices and they're on their own dedicated pins. Saving $75 caused a lot of extra wiring difficulties and in hindsight I would gladly pay the difference. Unfortunately by the time I realized this it also meant that I would have had to change my physical installation due to a different connector location and interference with other devices.
When mounting the encoder, it should be noted that there are a couple of adjustments on it that will need to be accessible after it is mounted. These may need to be adjusted when one is doing their bi-annual Mode C altitude check/calibration. Since my GPS unit is easily removable from the front without removing the actual instrument panel, I've mounted the encoder such that its adjustments are accessible via the openings in the GPS rack once the actual GPS unit is removed.
For Canadian craft: Note that the encoder and transponder need to be tested / calibrated by an avionics shop every 24 months per CAR 625(C).
ELT, Antenna and Remote
If I read the regulations correctly, these are required in Canada even for amateur built craft except when engaged in a test flight. Flight training units appear to have an exemption within 25 NM of the aerodrome of departure. I got an Artex ELT200. Not the cheapest available, but again a long-time player in the field with a proven small, lightweight design. There are special helicopter models with a six-axis "G" switch, but these are considerably more expensive than the single axis models.
Update: Although they're still available from various suppliers, it looks like Artex has discontinued the ELT200 model. This appears to be as a result of the shift towards the newer 406 MHz models.
One noteworthy item is that the installation manual actually recommends that the unit be mounted horizontal (to max of 25°) rather than at 45° like many other units in a helicopter. Supposedly this is to reduce false triggering due to the more sensitive switches in the TSO C91a units vs. the older C91 units. This poses a bit of a dilemma since CAR 551.104(f)(2)(ii) which governs the installation of ELT's in Canada states "When installed in a helicopter the ELT shall be mounted with its sensitive axis pointing approximately 45 degrees downward from the normal forward direction of flight." For now I'll go with the manufacturer's recommendations and possibly discuss this during final inspection.
When installing the remote on/test/reset switch in the console, it should be noted that it shows the power source as being from the "always on" bus; i.e. direct to the main battery. It would appear that this power source is only required for the switch's LED display and not for the remote switch to work.
One decision a purchaser must make is whether they wish to purchase a 121.5/243 MHz ELT and probably have to replace it in the foreseeable future, or pre-invest in a 406 MHz ELT which will meet the new standards. I chose to go with one of the existing models as the newer units were considerably more expensive when I purchased mine. I felt that as more of the 406 MHz units were introduced into the marketplace then their prices would start to come down. At this time, Artex has just introduced the ME406 unit which is about 1/3 the price of the other units that were available when I made my decision. The nice thing about the ME406 is that it's footprint is very similar to the ELT200 that I purchased, and although it is slightly wider (I believe about 0.4") the mounting holes are compatible. The one slight negative is that it looks like they changed the connector for the remote switch at the ELT end, but that's easily changed and I'll try to remember to leave a short service loop here for this eventuality. Note that the ELT200 requires a 3-conductor cable whereas the ME406 requires a five conductor or four conductor plus shield cable. I chose to completely pre-wire the remote switch for either ELT but I was one socket short for doing that and used a Molex 02-06-1103 socket (a -5102 gold one would have been preferable). My cable ended up as:
I need to investigate in the CARs whether the
actual ELT needs to be tested/re-certified. I seem to remember
something about every two years and I've also seen several
avionics shops advertising this service.
Update: For Canadians, CAR 625(C) is pretty clear ... ELTs need to be inspected every 12 months. Note that this is not a performance test that the pilot can perform, but rather a test by an avionics shop.
The ELT antenna normally comes with the unit and
I'll probably mount it relatively high on the passenger side
"firewall" rib ... if it's really needed, who's to
predict what side will be "up". I had thought about
mounting it on the tail boom, but thought twice about that due to
the longer coax run and the fact that the coax would have to
cross the frame to boom mount that could possibly shear in a bad
accident. Oops ... I forgot about the fuel tank above this rib
... guess I'll have to re-think this one a bit more. Then again,
reading the manual implies that the whip antenna is not
recommended for a helicopter application and one should use the
hard rod antenna instead (similar to a normal VHF antenna but
shorter). These are expensive antennas and cause a bigger dilemma
on where to mount them on the cab. Hmmm ...
Note that the HM406 manual states that the antenna should have a 24" ground plane extending in all directions (i.e. 24" radius).
Update: It looks like I'll eventually have to install a 406 MHz ELT but can temporarily get away with the 121 MHz ELT and whip antenna that I already have. Since this will be a temporary install (probably max two years), I'm keeping the install simple and not purchasing an expensive rod antenna. The whip will be mounted on an angled plate near the frontmost pillow block on the tail rotor driveshaft.
Update 2: The ELT antenna location continued to dog me but eventually I had to mount it so that I could go forward with the inspection. Hmmmm ... the inside of the bubble between the seats right at the top of the headboard actually appears to be a very viable location. However, I didn't want to mount a temporary (i.e. 121.5 MHz) antenna there, especially if it meant bonding something to the bubble. Eventually I mounted it on the top of the main frame near the first pillow block. Certainly not an ideal location but it should suffice for now.
Another consideration with ELT antennas is both their placement and routing of the coax. A COM antenna is mounted primarily in the best location for coverage and it may have a relatively long coax run. On the other hand, an ELT antenna is mounted primarily for crash survivability. This means that the coax should be as short as possible and not run across frame breaks or through bulkheads where it could be cut in the event of an accident. Different antennas require different considerations.
Although the 121.5 MHz ELTs are being phased out, the actual rules about mandatory replacement aren't that clear and seem to be a moving target. The one thing that is clear, is that satellite monitoring for them will cease in 2009. If replacement of the old ELTs is not mandated, there is still a reasonable alternative to the expensive fixed 406 MHz ELTs ... namely a PLB (Personal Locator Beacon). Companies such as ACR make small portable PLBs that broadcast on 121.5 MHz / 406 MHz and also include a built-in GPS receiver for accurate position fixes that are included in the 406 MHz transmission. These units are about the size of a handheld radio (or slightly smaller), use the latest technologies, can be used for other activities such as boating or hiking and are actually cheaper than the fixed aviation systems ... obviously their target market is much wider. By carrying them in a flightsuit or other personal attachment, they become part of the survival gear that is always carried with you even if you do a quick egress.
Another company that is getting into the more
reasonably priced (relative term) 406 MHz ELTs is Kannad.
I don't have any personal experience with them other than a very
enthusiastic rep at Sun-n-Fun. One difference between the Artex
and Kannad units is the battery chemistry; there was a battle
with Transport Canada and Industry Canada as to whether Artex's
LiMnO2 battery was acceptable ... it has now been approved.
It looks like the 406 MHz ELT market will soon be heating up. Pointer has announced models with an internal GPS and NAV interface with a target price of about the same as the competitor's prices without the GPS or interface. If I didn't already have my ELT, I would be waiting until near the time I actually required it before purchasing one.
I seriously considered the NAT, PS Engineering and possibly the XCOM (will require some field feedback) intercoms. One feature I was looking for was an adjustable "soft-mute" on the external input since I would like to seriously look at hooking a rotor speed alarm directly into the intercom rather than requiring an external interrupter-style interface. I know that some NAT models have this feature, and I'll look into the others. One thing that I have noted in most intercom wiring diagrams is that they recommend or require a set of microphone and headset jacks be directly wired to the radio and bypassing the intercom in order to have backup and also to trouble shoot any radio problems.
Originally I didn't include the David Clark intercom in my selection list. Now that I've looked at more wiring options, I see that the DC-COM 500 has a unique feature over most of the other intercoms that I've seen; namely it fully supports two COM radios and even allows for the pilot and copilot to commonly use one of the two radios or to "split" the usage such that the pilot is using COM1 and the copilot is using COM2. While I'm sure most builders don't initially plan on installing two radios, it might be worth considering getting a primary COM transceiver and a GPS/COM unit vs. a straight GPS as the incremental price on a GPS/COM is a lot less than a second radio. The negatives of this intercom is that it is more expensive than most of the others and is somewhat larger.
I have received an inquiry about the necessity of an intercom. I don't claim to have a lot of experience with these and it is obviously very dependant upon the type of radio (and its features) being installed. These units are connected between the radio and the headphone / microphone jack[s] and usually have provisions for one or more external inputs such as a second radio, CD player, etc. A few of the important terms that I have come up with when looking at the radio / intercom combination are:
Hot mike - This refers to the microphone circuit(s) always being active. While it will allow pilot / passenger communication, it also continuously picks up and amplifies any background noise.
PTT Intercom - Essentially the intercom circuit is based on a manual Push-To-Talk (PTT) switch and has the advantage that background noise is not amplified when the intercom function is not activated. However, I also find that these are a real pain to use and tend to inhibit communication. I've also seen some configurations whereby the switch is combined with the radio transmit switch and is such that a single switch has one spring-loaded position for intercom and additional pressure then activates the radio transmit function. If one was using this kind of switch, I think it would be prudent to consider that the passenger PTT switch should be separate from any radio transmit switch on the passenger's cyclic stick and preferably not mounted on the cyclic at all.
VOX - Voice activated circuit - These units have a circuit that attempts to monitor the ambient sounds and detect when someone is speaking which will then cause it to activate the intercom circuit without requiring a manual switch. When no voice activity is detected the units are quiet and the radio transmit function is via a normal PTT switch. The better units allow for uninhibited conversation while some of the lower quality units cause a bit of clipping when one first starts to talk.
Update: I found a good deal on a NAT AA86-002 (Odyssey) intercom which I purchased. Although this is a stereo intercom that is no longer manufactured, it has several interesting features that I liked; namely VOX with a front panel adjustable mute and volume level for the music input which I'll possibly be using for rotor alarm inputs. It also has a partial mute option for intercom, radio or neither in addition to all the appropriate LED indicators.
This was a difficult decision for me. Looking at a side view, there are two obvious mounting locations; under the belly and on top of the tail boom. I remember hearing that the boom mount is better for ground transmission (but can be blanked by the cab and mast in the air, especially forward and down) and the belly position is better for in-the-air transmission (but can be blanked when on the ground). I think the ideal would be both with a switching unit for ground vs. air, but this appears to be a no-no. Thus neither of the choices seems to be ideal. At this time, I'm heavily leaning towards the belly mount since in-the-air communication is where most communication will be, especially the weaker long range ones. Worst comes to worst, I may consider a hand-held for on the ground transmission. Another consideration for antenna placement is whether one will ever install some kind of a belly pod storage device. The ones that attach under the belly would probably physically, and possibly electrically, interfere with any kind of a belly COM antenna and if there is any amount of metal [with]in the pod they could also interfere with a transponder antenna.
Update: I've done a little more research and it appears it is possible to have one radio switched between two antennas. I've seen references where at these frequencies they just use a well-shielded SPDT switch and the more classic approach seems to be to use a 50 ohm coaxial relay similar to what the ham radio operators use. Neither of these alternatives have a transmit lockout and for now I think I'll stick with the one radio, one antenna approach.
For those with the opposite problem of two radios and only one antenna, there is a certified solution in the Comant 601 Duplexer. This is an expensive automatic unit that allows the single antenna to switch between the two radios when triggered by the radio's transmit inputs. It looks like Bob Archer also makes a similar unit (SA-010) and although I've seen a picture and price ($200), I haven't been able to find the technical specifications.
For those who are using an ICOM (or perhaps other brands) handheld radio there is an Antenna Switchbox available which allows for the handheld radio to tap into a standard aircraft VHF antenna circuit. It would appear that it does this by disconnecting a panel mount radio from the antenna. I recall reading several articles that all referred to greatly extended range and clarity when using a fixed antenna with a handheld vs. the supplied "rubber ducky". There was also an article by Jim Weir in Kitplanes that described a simple panel jack to perform this function. Another variation on this technique is in this article by Bob Nuckolls.
The mounting location will determine the style of antenna used. If it's on the boom, one could use one of the standard whip (fiberglass or stainless) types and rely on the boom tubes to act as the ground plane. On the belly, one would have to go with some kind of a bent whip (or very specialized blade i.e. $$$) style in order to retain some ground clearance. The problem is that most of the specifications I've looked at show the bent-whip style as having a poor VSWR of ~3.0 vs. the typical 2.0 for a straight whip.
I managed to find a reasonable deal on a Dorne & Margolin DM C70-4 (interchangeable with the Comant CI 122) that is a little taller (8.9") than some of the other bent-whip style antennas but has a listed VSWR of 2.5. How much of this is marketing vs. reality I'll have to wait and see once it's installed; also I'll have to see how comfortable I am with the clearance under the belly.
One thing to be very conscious of with a boom mount is the potential of noise from the strobe since these are usually electrically noisy devices that can easily result in radio noise. I may be overly cautious, but I'm using shielded wire for the strobe plus a shielded lens and would advise that no antenna be mounted in close proximity.
I thought I had this antenna issue resolved, but the more I looked at the boom the more I realized that I would prefer to have a welded mount if I were to place an antenna there. Since its much easier to do this before painting, and also to run the extra cable during initial wiring, I've decided to actually mount two antennas initially, both the belly mount and a boom mount. The boom mounted one will be a Comant CI175; one of the reasons being it has a slightly smaller mounting footprint and will be mounted on the original strobe mount plate (with a small extra piece of plate welded to it). Which antenna becomes the primary one remains to be seen after testing. Note that the new Comant antenna I received did not have a gasket, backing plate, BNC protection or template which the D&M unit had ... not a big deal, but also not as complete.
Antenna Mounting Considerations
Most helicopters will use what is known as a 1/4 wavelength monopole antenna which is essentially an antenna rod that utilizes it's mounting plate to act as a ground plane that forms part of the system. Under ideal conditions, this ground plane would be a flat metal plate at 90° to the antenna rod and have a radius of 1/4 wavelength. Instead of going through the calculations, one can usually use the length of the antenna as the radius of the ground plane circle. In the case of a transponder antenna, this is about 2.75" and in the case of a VHF antenna it's about 22". There are also other mounting considerations such as the distance between antennas (ideally 3' or more), length of the coax to the transmitter / receiver (shorter is usually better but sometimes there is a minimum length), etc. One also needs to remember that most aircraft systems use frequencies that are considered line-of-sight from the antenna to the source or destination. Any kind of structure on the aircraft or on the ground that blocks this line-of-sight will degrade the system's performance.
Unfortunately, it seems that most antenna installations are a compromise due to physical constraints. From my perspective, there is also a lot of voodoo involved since I've seen antenna designs and installations that defy all the documentation that I've read yet are still extremely effective. It's my understanding that a tube structure like the Safari tail boom also creates an effective ground plane. For a tail boom mounted antenna, I would first test it's effectiveness before adding any extended metal plate(s) that might interact with aerodynamics. When one looks at Robinson and Rotorway antenna installations, many of them are mounted on a relatively small tubular boom yet they're quite effective.
If one is mounting both a VHF and transponder antenna on the belly pan there will be some kind of compromise involved. The first decision is which antenna is at the front and which one at the rear. I chose to mount the transponder antenna rearwards since the Garmin installation manual actually specified a 3' minimum spacing between the transponder and the antenna. In order to maximize the distance between antenna's, I mounted the transponder about 3" ahead of the firewall and slightly off center (didn't want to interfere with my paint scheme). My bent whip VHF antenna was mounted about 22" back from the front of the belly pan and just slightly off center (to the other side) to allow coax clearance on the heater SCAT tube under the floorboard.
When physically mounting the antenna, one should carefully read the manufacturer's instructions. AC43.13-2A also has some very good information. Most antenna's require that they be electrically bonded to the groundplane either through a metal base plate or via the mounting screws. On a painted structure this means that some paint will need to be removed. External tooth stainless star washers can also be used to help maintain this electrical bonding. While it may be tempting to paint an antenna to match a paint scheme, this should be avoided since the the pigments in some paints can interfere with the antenna's effectiveness.
I've seen several ELT antenna installations which are practically useless for any kind of efficiency; i.e. mounted on the inside of a metal aircraft right against a metal bulkhead. These are also monopole antennas that require a ground plane. While one can't predict what would be "up" in a crash to optimize polarization, shielding an antenna with a bulkhead or metal side panel with no ground plane certainly reduces the odds of it's effectiveness.
GPS antennas need to be mounted on the top of the craft such that they have the best view of the entire sky. Again, there will be a compromise and mounting them further away from the mast will help to reduce blade interference. In my case, I will be trying a mount that's towards the top of the instrument pod on the front side of it.
N.B. The above information is extremely general and overly simplified. If a builder has any doubts about antenna installations they should consult with someone who is experienced and qualified in this field.
Question: One of the questions that I have but haven't really pursued is how the ground plane relates and interacts with a bent whip antenna. For example, does one allow for 1/4 wavelength ahead of the antenna and another behind the trailing end or does one just go with 1/4 wavelenth centered at the mounting base. If anyone reading this has an answer, I'd really appreciate an email so I can expand my knowledge.
As an alternative to RG-58*, I'm using RG-400 for my transponder and my radio. It's a lot more expensive, but is specified for the transponder (max 8.8 feet) and is used by others for the radio. Since I already had to get some for the transponder and I don't believe in wasting what RF "power" we already have, that's what I'll use on my radio unless someone can demonstrate why not. The following link gives an interesting graph: coaxloss.pdf. Also note that cable length DOES effect its loss; all cables should be kept as short as reasonably possible.
I prefer to not run antenna cables in the same bundles as other wiring since the braided shielding usually does not have 100% coverage (about 85% for single shield and 90% for double shield) and there is some RFI leakage. Also, I believe it is good practice to try separate individual antenna cables, especially something with transmit capability (radio or transponder) and a low-level receive-only one such as GPS. In the Cabin section it can be seen how I've routed the transponder and boom antenna cables through conduits under the floorboard in order to avoid being near the various wiring and devices within the switch panel console. Note that coax cable has a minimum bending radius and exceeding that value will compromise performance of the attached units; I believe RG-58/C/U and RG-400 have about a 2" minimum bend radius. It is also extremely important to not compress or kink the cable in ways that effect the normal shape/size of the shielding. Properly sized adel clamps should be used to support the coax wherever possible and if the builder insists on using tie-wraps, then they should be careful not to over tighten them which can crush the shield and distort the inner insulation.
I looked carefully at adding a GPS unit such as the Garmin GNC 250XL (or GNC 300XL) that are a panel mounted moving map GPS and COM combination. While I'm sure I'll eventually add a GPS unit, for now I've decided to defer its acquisition until I really feel I need it. By using a separate radio there's no immediate demand for a unit like this and for the price difference to a unit without a COM (i.e. GPS 150XL or GPS 155XL) it probably makes as much sense to get the one with a COM feature that would effectively become COM2. In the meantime I'll keep an eye out for well-priced unit and a friend has offered to make arrangements for his handheld GPS that he isn't using. The only decision for the time being is whether to leave a panel opening for a fixed GPS ... I'm thinking I probably will.
Update: I think I've found the best balance for the time being. I found just a Garmin XL rack on eBay for the right price and will mount this in the panel. This way I can make the appropriate cutout and mounting rails and if/when I purchase an actual panel mount GPS it will just be a matter of finishing the wiring and sliding the unit into the pre-mounted rack. The other reason I had for doing this is that I'm thinking that my encoder will be mounted on a "shelf" above the racks that will be held in place by the rails and a rack support. Thus I can install the encoder, possibly using the racks for support, without worrying about interference.
Update 2: After convincing myself that I would just mount the rack initially, I came across a really good deal on a brand new GNC 250XL. In fact, it was a good enough deal that I bought it. Now the only question I have is when to actually install the unit as it won't be needed for the initial testing and I'd rather keep it in "new in the box" state until I actually can use it. There are also some good deals to be found on factory reconditioned GNC 300XL and GPS 155XL units which are repeatedly show up on eBay and various avionics dealers such as Van Bortel.
I made up my own harness for this unit and I was surprised to find that the D-Sub 37 housing actually interfered with part of the backplate. I'm not sure whether Garmin has changed the supplied housing, but I found that I had to mill down one corner of the one that I received.
My radio stack now has the GPS/COM, radio and transponder mounted one above the other. All of these units give off heat, especially when transmitting, and since the life of electronics is directly proportional to heat I do have some concerns about cooling. Without some form of forced air, these three units will definitely get warm as they will be in an enclosed pod that will be exposed to the sun. I've mounted a fan in the bottom of my pod to introduce fresh air and it's airflow will directly hit both the transponder and the radio. However, the GPS/COM is mounted above the much deeper radio and I believe that it will probably require an avionics fan that delivers forced air via a 5/8" hose. I'm still investigating mounting locations since the most logical ones would put an electric motor right beside the magnetometer in the Dynon EFIS if I choose to install it in the pod. I believe a better place will be under the switch panel or even in the rear cabin bay. I've also chosen to add grounded copper mesh in the main fan hole to act both as a finger guard and also to try filter any EMI/RFI entering or escaping from the pod.
Interesting trivia: I was reading on one avionics shop's website where they'd done a test by leaving an aircraft out on the ramp on a sunny day with OAT of 77°F. After two hours they measured the temperature behind the panel ... 135°F. The 58°F differential certainly gives some interesting food for thought.
Update: For the initial installation, I've chosen to add the 5/8" hose to the GPS/COM but rather than installing a separate fan, I'm just routing the hose so that it's open end is directly above the existing fan. Certainly this isn't nearly as effective as a proper avionics fan but it's simple and cheap. If it proves not to be effective enough then I'm prepared to add a separate avionics fan (in fact the power lead is already wired but just capped).
Headsets / Helmets
This is another area that I have not made a final
purchase decision on. At this time I'm inclined to go with ANR
style earsets and I've heard good things about the upgrade kits
from Headsets Inc. as
well as some of the ANR sets from the mainstream headset
manufacturers. The main thing holding this back (besides the cost)
is that I will probably be getting a helmet rather than a headset.
After reading through various accident reports and lurking on
some of the forums with commercial pilots, it would appear that
many fatalities are the result of head injuries from what would
otherwise be a survivable accident. The constant use of a visor
also appears to increase ones odds of surviving a bird strike
which may be a rare but real possibility. At this time I'm
leaning towards getting a Gentex SPH-5 dual-visor helmet from Flight Suits
although I've also looked at various helmets from Alpha
and MSA (CGF) Gallet. I've
also found this reference to the Comunica
helmets, but I have no personal experience or further information
on them. For those looking for used Gentex helmets or parts, they
might also want to check with Flighthelmet.
Sidenote: I recently ordered a couple of additional small parts from Headsets Inc. Even though it had been several years since I'd last dealt with them, they still had my address information on file ... while they may not have online ordering, it was a real quick, simple and pleasant transaction over the phone.
Update: I managed to get a good deal on a Gentex SPH-5CG helmet (basically an SPH-5 with metallic blue finish and visors reversed: i.e. the clear visor as the outer vs. inner one). I've replaced the liner and changed the microphone from the military M87 dynamic type to a civilian electret. While I could have just changed the earphones to ones with civilian impedence (17 vs. 300 ohms) I chose to do the Headsets Inc. ANR upgrade while I had the earcups already out. The upgrade kit definitely seems to be more oriented to headsets rather than helmets and its a bit of a pain figuring out how to physically run the wiring. Until I've got my ship complete, I'll be using a helmet-mounted battery whereas I'll install panel power in my craft. I've also noticed that it appears that Flight Suits is now offering this same conversion system for roughly the same price as the kit but including installation. The key difference in price is the integrated helmet ANR cord which is also available separately and should definitely be considered if one wants a relatively simple installation.
As far as a passenger headset goes, I'll probably
go with a Peltor
7000 Pro GTH or 7000H Sport LE. I don't have any solid factual
reasons for this other than I used them during flight school and
I was impressed with their comfort, sound quality and how well
they stood up to the various abuse by students.
Update: I managed to get a good deal on a reconditioned Peltor 7000 Pro GT headset ... approximately 1/3 of the normal asking price and I can't find a single thing wrong with it. The only issue is that it has the dual jack fixed wing style. For me, that is not an issue as I have a spare U-174/U plug and the "Y" connection from the single straight cable to the dual jacks is just about at the ideal length for a helicopter cord. A quick cut and solder job and it should be exactly the same as the GTH model.
Right now I'm dealing with a strange headset / intercom problem. Both my headset and another person's helmet have mics that go extremely scratchy and basically unuseable when two devices are plugged into the intercom and the radio is turned off. Alone on the intercom they're fine. I've tried all permutations with three other headsets, my helmet plus another intercom. In all cases, this one headset causes the issue. As soon as the radio is turned on, it's perfectly fine. Stay tuned, the debugging contintues but if anyone has an answer I'd sure appreciate hearing it.
While most fixed-wing aircraft tend to use separate headset and microphone (with PTT) jacks, helicopters tend to use a single U-174/U plug and U-92 style jack. Obviously it's the builder's choice which style to go with, but I chose to use the single plug system. I do have a dual plug to single plug adapter in case I ever need it, but I figured that anyone else trying to plug their own headset or helmet into this system would probably be a helicopter person and using the single plug. I also have a single plug to dual plug adapter in case I ever want to use my helmet or passenger headset in a craft that only has dual plugs.
The plugs and jacks are available directly from Nexus (TJT-102, TJ-120, TJT-120 etc. for panel mount jacks) who are very easy to deal with and their prices for low volume on jacks are reasonable (~$8-$9). The one possible problem is that they have a $35US minimum order. I actually ordered a set of both the TJ-120 flanged jacks and the TJT-120 threaded jacks. While I'd prefer to use the flanged jacks for a more secure mounting, due to the extra size of the flanges I'm not sure if they'll fit in the housing that I was planning on using; they're oval shaped 5/8" x 1-3/16". The threaded jacks are 23/32" diameter, but they have a large nut and washer (just under 1" diameter) that needs to be used behind them.
I came across the website for Comm Innovations and it would appear that they also offer the various jacks, plugs, adapters etc. with web ordering. I have no direct experience with this company other than coming across their website. After reviewing their online order policy, it would appear that the minimum order is $50US for domestic sales and $150US for international sales. Unless one has something else to order, this is way above the $16-$18 required for two jacks. Although I couldn't find it on their website, I noticed in the American Avionics catalog that they list the TJ-120 (P/N U92B/U-R @ $13.95) and the TJT-120 jacks (U92B/U-F @ $16.95). Due to the price, I haven't checked further on their sales policies. Also, Headsets Inc. now lists the U-174 plug ($14) and U-92 jack ($19) in their pricelist ... they also list the U384/U385 five conductor plugs/jacks which would allow for the power connection but using them could create problems interfacing to other standard headset or helmet plugs.
After trying to locate these jacks, I think the best approach would be to first call any local helicopter maintenance shops and/or avionics shops and if they can't supply them, then just order direct from Nexus. One could order an extra jack/plug for an extension cord in order to meet the minimum order amount. If someone has the name of a low-volume mail order supplier, I'm willing to add it here.
This is the housing that I'm using to hold the headset jacks. The electrical module in the photo is an ANR headset power supply which will be mounted to the backside of the housing. The mounting holes for ANR power are not shown here as I hadn't made the nylon insulating washers for them at the time the photo was taken. The power module shown is the standard one for a single heaset whereas I chose to make a unit for two headsets.
There seems to be some ambiguity as to the wiring of these plugs/jacks as I've seen slightly different schemes and also a reference that says they're wired differently for ground personnel. After checking various patch cords and references, so far the consensus seems to be as follows and that's what I'll be trying:
I reviewed the Robinson R22 Maintenance Manual and indeed it would appear that this is how they wire their jacks. Interestingly they appear to use 2 conductor shielded cable to the jack with #3 & #4 connected together and to the shield which is then listed as going to a frame ground. Perhaps this is just due to the diagram rather than physical implementation, but I would think one is much better connecting the ground (i.e. Lows) right at the intercom. I've noted that at least one intercom (PM1200) installation wiring diagram says that the use of separate Mic/Headphone shielded cables is mandatory in order to avoid cross-talk for this high noise environment system. Also most of the wiring diagrams I've seen show the Low lines as being a conductor within the cable which is connected to the shield at ONE END ONLY. It may be a bit on the conservative side, but I will be running two 2-conductor shielded cables to each jack, one for the microphone and one for the headphone.
Tip: This is not required for the Nexus helicopter jacks, but if one is using the standard aviation two jack per headset arrangement, they should use insulating washers between the jacks and any metal surface they're mounted on. This will prevent a ground loop which sometimes manifests itself as a buzzing or whining in the headset or microphone circuits. Special nylon shoulder washers are available but typically they need to be ordered separate from the jacks. I'm also choosing to use this kind of insulated mount for my ANR power outlets.
ANR Power Supply
I've been using a 9 volt battery in a small pouch attached to my helmet and while it works well, it's more batteries to monitor and make sure they're okay. Headsets Inc. does make a module for permanently mounting in the aircraft but I found it to be a bit big and awkward to mount, especially since I planned on installing two modules. I decided to make my own dual supply that attaches to the back of the headset jack box. Basically this is just a pair of DC to DC isolation converters that insulate the ANR power from the aircraft power supply. It should be noted that these converters are relatively noisy from an RF standpoint and I chose to mount them well away from all radios and antennas. I've also surrounded them in a metal shield to try contain some of their noise.
Cell Phone Interface
I have read in various forums about pilots wanting to connect a cell phone into their intercom circuits and various degrees of success in doing so. While I do carry a cell phone for emergency usage, I have the same opinion on the useage of these in aircraft as I do in cars; they should NOT be used when the vehicle is in motion. Somehow I can just see getting myself into a tricky situation and suddenly getting a ring from a wrong number ... no thanks. My phone is basically used for outbound calls, so I have no qualms about turning it off but having it available if the need arises.
I also don't know the legality of using a
standard analog cell phone in a non-emergency situation while
airborne. From a technical perspective, I believe it can cause
the cell system various problems since there can be multiple cell
sites that may be receiving a strong signal which normally
doesn't occur on the ground.
Update: I've since read an article by someone who researched this and came to the conclusion that in Canada there does not appear to be any technical or legal reason for not using a cell phone while airborne in a private aircraft. Although it can be used for contacting ATC this should only be used in a NORDO emergency.
There is one case where I may need a cell phone, but on the ground: The Class D airport I normally fly from actually butts against (and is veiled) by a Class C airport and if one plans to enter the Class C airspace, then a unique transponder code is required. This code from the Class C airport is required before takeoff from the Class D airport and is arranged for before the flight via a special phone number. There is also a local heliport right at the edge of the Class C control zone that also has this phone ahead requirement.
I have seen various commercial interfaces to connect a cell phone, but I've also seen feedback that leads me to believe some of them are not very effective. XCOM now appears to stock a unit (Flightcell 2Go) that they've given a very favorable description of in their newsletter, but I have no further information.
Handheld Portable Transceiver
During my training, I purchased an ICOM IC-A5 handheld radio when the local supplier had them on sale. I found that listening in on the local Class C airport terminal frequency really helped to "tune" my ear to hear unexpected and fast bursts of information. Even now, I occasionally turn the radio on when I'm working on the electronics bench and it helps to keep my ear in tune. Eventually this radio will probably become part of my survival gear, especially if I'm doing any longer cross-country flights or mountain flying. Although the radio came with a Ni-MH rechargeable battery pack which has a pretty good storage life, I also obtained a battery case for use with standard AA cells that will also be part of the survival kit along with a couple of sets of long-life alkaline cells. As part of the purchase sale, they also included the optional headset adapter and I've used this to test both my helmet and headset when used in conjunction with a dual plug to single jack adapter.
Note: Although I've read lots of references about pilots using handheld radios in fixed wing aircraft, this really isn't very practical in a helicopter unless it's fully wired into a headset, a fixed antenna and a remote KEY switch.
The kit came with a complete set of VFR instruments plus their various sensors and I received a combination of Westach and Falcon gauges as shown here. For a newcomer to aircraft ownership these seemed to be an impressive set of "real" gauges. Now that I have more experience I would definitely change the choice of instruments ... probably to the point of not ordering the Safari Instrument Kit. I felt that two of the instruments were not suitable for use in my craft (tach, CHT) and one of the quad guages (the one with amps) was defective when I performed my electrical checks. It would appear that CHR's choice of gauges for the kit was heavily influenced by cost rather than functionality and reliability.
I thought I'd add a quick word here as I've seen these kinds of instruments mounted both from behind the panel and also from the front. Either will work, but normally they're mounted from behind and I think this is aesthetically more pleasing as there is only a single round hole plus the four mounting screws showing. Since most panels are removable for access, the only advantage I can think of for front mounting is if one is extremely space limited behind the panel and has an interference issue requiring about an extra 1/2" clearance.
There are special mounting clips, sometimes
called "grasshopper" nuts", that are available for
instruments that don't have threaded studs (i.e. most). These are
inserted into the mounting hole and have a captured nut, but
still have room for the mounting screw to pass through. There are
also some rings available that fit onto the back of the
instrument via double-sided tape and provide threaded holes.
Personally, I'm fine with just using a bolt/nut combination, but
it does require rear access in order to (re)tighten the nuts.
Update: I now realize why some people choose the special mounting hardware since once the various wiring and other instruments are installed, it can be very tight access trying to reach the nuts to hold down instruments. I used hemostats and nut drivers which caused no problems reaching the nuts, but I do understand the concern.
The Westach gauges came with ferrous mounting screws and I changed these for brass ones ... MS35214-25's (6-32 x 3/8") should be fine. Although most of the Falcon gauge mounting lugs will accept 8-32 screws, the CHR Instrument Kit provided MS35214-31 (6-32 x 1") brass screws. I set my panel up to accept the larger 8-32 screws, but later decided that the extra size and weight of the larger screws wasn't required. I did find that by using the 8-32 screws to initially locate the Nulite ring and instrument that it helped to center everything ... the 8-32 screws were then replaced one at a time with 6-32 screws.
While some of the gauges have green/red bands applied to their faceplates, others do not. I've chosen to use some vinyl instrument marking material to add the following markings to the "glass". While this technique does introduce parallax errors, my primary purpose was to just provide reminders.
Airspeed - A red line at 100 MPH (Vne) and a red band above that. A blue line at 60 MPH to indicate the ideal autorotation speed; this gives a quick reference and is also of use for pilots who are not familiar with the Safari POH in detail.
Manifold Pressure - A red line at 26". This is due to the fact that my engine can develop more than 160 HP at altitudes less than about 4,000' and can thus exceed the transmission rating. From the engine graphs, this red line corresponds to about 160 HP.
Tachometer - I added a yellow line to the rotor side at 400 RPM due to a known resonance issue. Due to parallax this really isn't nearly as meaningful for accurate feedback as it is for reminding the pilot that there is a speed to avoid. With the ranging on my tach, this corresponds to ~83% RRPM.
Carb temperature - I added a yellow band from 5° to 41° F. This was a best guess and based on the R22 yellow range of -15° to 5° C. Other instrument references I've seen have used 10° to 40° F, but UMA seems to use 15° to 50° F. Note that the various common icing curves are based on ambient temperature and dew point rather than the actual carb venturi temperature which is what this gauge is monitoring.
I know it is easy to just wire an instrument sensor to a gauge and assume that it is accurate so as to continue with the wiring and building process. However, I believe this is just asking for trouble unless each instrument and sensor is checked against a known reference and I refuse to believe an instrument's reading until it has been checked. The various pitot / static instruments can be checked at the same time as the initial altitude encoder calibration is performed and the tachs can be verified with either a portable optical unit or with a dynamic balancer. Note that CAR 625(C) requires that altimeters in Canadian craft operating in "transponder airspace" must be recalibrated every 24 months. The fuel senders and gauges are calibrated as part of the probe installation process and they can be calibrated using any kind of tube that can hold fuel to a depth equal or greater than the probe length. That leaves the thermistor and thermocouple probes which tend to be the most problematic.
Many builders are using 40 to 60 amp alternators and the CHR-supplied gauge and shunt are designed and labelled for alternators with a maximum output of 30 amps. I'm using a 40 amp alternator and without changing the specialty quad gauge, there are two alternatives:
Just use the gauge as is and hope that if one ever gets into the +/- 30-40 amp range that there is no damage to the meter
Change the shunt to one that is calibrated for the correct amperage range. While this should have a placard change as well since the gauge is labelled as +/- 30, the key item is that the meter range will reflect the alternator range. Unfortunately, Westach only appears to offer 30 amp and 60 amp 50-millivolt shunts. The B&C Specialty shunts are a bolt-in replacement and are available in a wide variety of ratings ... I chose to replace my CHR-supplied shunt with a 40 amp unit.
The various Westach thermistor sensors get progressively more sensitive to resistance the higher they go in the heat range: the difference between 0°F and 10°F is 6.8K ohms whereas the difference between 200°F and 210°F is only 41 ohms. Reasonable lengths of appropriately sized wire should not significantly affect their readings but care must be taken to ensure a good ground of the one lead. While the grounded lead of these sensors could be grounded anywhere, I chose to run both leads back to the instrument and ground the sensor to the same wire that provides the ground for the instrument. The OAT and Carb Temp sensors / gauges can be checked by comparing them to ambient temperature and also by immersing the probes in an ice bath (i.e. 32°F). The oil and transmission temperature sensors / gauges can be checked by immersing the probes in boiling water (212°F derated for altitude and pressure i.e. 204.8°F at 4,000' and 29.92" Hg).
The CHT thermocouple probes also need to be checked as they are also prone to false readings due to bad probes and/or wiring issues. While trouble shooting can be done with various tables and meters, it is best to check the calibration with the thermocouple in its fully wired condition right to the actual gauge. Because of the higher temperatures involved, this is normally done with an oil bath. One thought I had on this is the use of a small deep fryer (yes vegetable oil should work) and the use of an accurate candy thermometer. I have a small one that's good for around 400°F and I'll post the results here if I decide to use it.
Note that the supplied CHT gauge is of the non-amplified type and is not compensated for ambient temperature. According to the documentation, it has been calibrated for the use of type J thermocouples with the reference junction (i.e. wiring connectors) at a temperature of 75° F. If the reference junction is at a different temperature then the reading will be offset the corresponding amount i.e. connectors at 0° F means the gauge will read 75° F high. Considering that it is reasonable to expect my craft to see a 100° F ambient temperature spread and that due to lead length the reference junction will be outside the cabin or in the unheated rear bay, this needs some more examination if any useful information is to be obtained from this gauge. As a pilot seeing a gauge approaching the redline, I have more important things to do than mental calculations of offset and what the true reading should be ... the gauge is either accurate or it isn't, period. To move the cold junction reference physical location, I investigated the option of using proper type J thermocouple extension cables that terminates right at the instrument which is in the instrument pod and warmed by the cabin heater and avionics. If my calculations are correct, this is not viable since the resistance of the extension cables will introduce a calibration error of ~12% whereas the reference error is in the range of 0-18% ... not a good solution.
The more I've investigated this problem, the only viable solution I see for an accurate gauge in a machine exposed to significant ambient temperature ranges is to use a totally different gauge that contains reference temperature compensation. I've looked at a lot of alternative CHT instruments and the following are the reasonably priced ones that I'm currently considering: AveoMax TC2 (Quad CHT/EGT $198 list) or TC3 (12 channel CHT/EGT at $264 list) and the Aerospace Logic CHT100-4[V][BP] ($372+ list). The Aerospace Logic compensation is within the gauge and contrary to their wiring documentation, I don't believe it can maintain the claimed accuracy unless thermocouple extension wire is used. I believe the AveoMax instruments are actually the same ones produced by MGL Avionics and the smaller TC-1 would also be viable. Also note that the AveoMax instruments use an octagonal cutout ... I believe they'll work okay in a round cutout but just won't be as aesthetically pleasing. The above prices don't include the probes and both would require the use of thermocouple extension wire (I ordered EXFF-J-20S-TWSH from Omega) in order to move the reference junction location to the back of the instrument. Also note that thermocouples produce very small voltages that can easily pick up interference ... at least one install manual specifies that these should be routed at least 1" from any other wiring. Since that would be extremely difficult, I'm using twisted and shielded wire.
Update: I decided to get the Aerospace Logic CHT-100-4V gauge since I prefer the looks and features of the gauge. The [V] is a $50 option that adds a voltmeter as I realized that there is no voltmeter elsewhere in the instrument package and it sometimes comes in handy to diagnose issues with the battery and alternator. The one negative with this gauge is that since my panel was already finished, I also had to get a hole reducer to go from the 3-1/8" Westach gauge to the new the 2-1/4" gauge ... I used an MK-623 from Aircraft Spruce (p/n 10-00343) and although it's listed in the catalog as anodized black, the one I received was raw aluminum and needed to be painted. Note that the developer of these instruments maintains an eBay store (24x7-Avionics) and the prices are typically better than most of the normal aviation suppliers, although his shipping isn't always as fast. He's also very willing to work with eBay clients to create custom packages of the various offerings.
Actually there is a bigger negative with this gauge that I've discovered the hard way. I thought that I could continue using the CHT probes that I got with my Safari Instrument kit. Turns out that this gauge requires the use of GROUNDED probes. While these are available, they're not as common ... Westach makes them with a "G" suffix but I haven't seen them in any catalog. What's even more confusing is that companies such as EI specifically state that they avoid the use of grounded probes due to noise issues ... interesting dichotomy of opinion between manufacturers. The bottom line is that one should get new probes with this instrument if they choose to go that route. The other alternative is to ground the red wire (black heatshrink on Westach probes) but I really don't know if that effects the accuracy. This grounding "trick" is exactly what has to be done with the LASAR® dual thermistor / thermocouple probe. Eventually I broke down and got three more probes from Aerospace Logic that were of the grounded type.
The supplied analog dual tach that I received is of the generator driven style whereby no other electrical source is required thus allowing its use even during a total electrical failure. I have heard many reports of issues with it's accuracy and stability, but I can't give first-hand feedback. While I truly like the idea of a tach that does not rely on the electrical system, I'm choosing to not use this one. It's my opinion that when testing, transitioning and building initial time on a new machine it is very important to have accurate instruments that I can trust.
CHR is now offering the combination digital Rotor-Tach Alarm for sale to builders and the description indicates that it is included in new kits. From its picture, it would appear to be very similar to the new Westach offering with calibration and markings for the Safari i.e. actual RPM/RRPM values instead of percent and green range from 460-500 RRPM. There are differences in the electronics between the Rotorway and Safari units since the CHR unit retains the use of the 303DGT generators while the Westach/Rotorway offering normally uses Hall-effect sensors. The key differences between the new CHR unit and the original analog tach is that it uses digital signal processing, has an expanded scale and has high/low alarm LEDs with a horn output. Most importantly, it uses the frequency of the tach generator rather than the voltage which makes it much more stable and accurate. As a retrofit, the price at this time is listed at $597 plus 2*$49.50 for the sensors if one doesn't already have them.
The more I looked at the picture of the new tach from CHR, the more I knew something was bothering me about its layout and markings. CHR has opted to reverse the layout from the Westach/Rotorway offering with engine on the left and rotor on the right. While this matches the arrangement on their previous gauge and on the R22, I have to wonder from an ergonomics standpoint whether it would be better to have the rotor on the left since that is the critical one and closer to the pilot. More subtle, but much more significant to my way of thinking, is that CHR has opted to make three different scales in their migration from percent to actual values. One of the features of the Westach digital tach is that it has an expanded scale in the important area above 90%; in fact, 90%-110% range is approximately one-half of the scale and I think that's great. On the CHR scale, the markings from 260-400 RRPM represent 20 RRPM increments and are very close together; the markings from 400-500 RRPM are much further apart and still represent 20 RRPM; the marks above 500 RRPM have a different spacing again, and represent 10 RRPM. Personally, I find this very distracting and have to really stare at it to fully understand a reading. I find it hard to believe, but the two needles do not appear to be linearly joined throughout their ranges which could make it very difficult to decide if one has clutch slippage (I've talked to the supplier of these tachs and each side is calibrated to the actual markings). Although both tachs have an ~8% green band, the band on the CHR tach appears to be narrower due to its lower positioning and it's bottom-of-the-green is at 460 RRPM whereas the updated POH states 470 RRPM. It also would have been nice if CHR had opted to add a yellow caution/avoid line at 400 RRPM, but that is relatively easy to do with external labels. The high alarm setpoint is fixed at 502 RRPM (100.4%) and thus its more of a top-of-the-green warning rather than a true overspeed alarm. Needless to say, I'm not impressed with this tach's layout and have decided that I will NOT be ordering one.
Update: I've chosen to have the original developer of the digital tach perform a conversion on my analog tach. It has the digital electronics, a standard % scale, adjustable alarm setpoints (92-98% and 102-108% in 1% increments) and the enhanced power protection. Since the green range is 96-104%, I chose to set 100% at 480 RRPM which gives a green range of approximately 460-500 RRPM and allows good ranges for the adjustable alarms. I've chosen to set the alarms at 97% (466 RRPM) and 107% (514 RRPM). We had discussed the use of Hall-effect sensors, but I was assured that the standard 303DGT tach generators are accurate and drift free when used as a frequency generator rather than a voltage generator. If other owners of the CHR-supplied analog tachs are SERIOUS about this conversion, I can supply them with more details.
Update 2: One of the things I've never liked about the Westach gauges is their plastic cases ... seems both cheap and flimsy to me. When my compass was giving me trouble, I decided to take another look at my panel and the location of various instruments. I'd been very careful to only use non-ferrous materials but the tach is by far the closest electrical instrument to the compass. Although I could have switched immediately to the R22 tach with it's metal case, I chose to continue using my modified digital tach since I was satisfied with it's calibration and didn't want to make too many changes at once. The one change I did make was to wrap the tach in magnetic absorbing metal (uMetal). This is available in thin sheets (.005") from Aircraft Spruce.
Sidenote: It's my understanding that with the release of the Safari 400 that CHRI is also releasing an updated tach. I have no further details or pictures but it should be noted that the rumour is that CHRI is now operating the Safari 400 at a higher rotor RPM which would effect both the tach markings / calibration and the alarm horn settings.
I had briefly considered the tach from an R22 as I've never heard of an issue with these units. They're an electrical unit with an alternate power source through the clutch switch in the event the master switch is turned off while the clutch is still engaged. The engine RPM input is via points in one of the magnetos and the rotor RPM input is from a Hall-effect sensor detecting two magnets on the main rotor gearbox input yoke. Due to the different engine and rotor RPM ranges in the R22 and Safari, an R22 tach would need to be recalibrated and originally I didn't believe this was easily accomplished. From the set of maintenance manuals that I have, it would appear that the early A792-1 tach is only adjustable at the RHC factory while the A792-2 tach is pre-set but allows some adjustment of the rotor rpm via an adjustment screw on the back. The A792-3 tach is the one used in the Beta II and the main difference being that it has a narrower green range (3% versus 7%). Although I've seen reference to an A792-4 model, I have no idea what the difference is. Obviously these units are factory adjustable, but I wasn't about to possibly destroy one just to verify whether they can be adjusted to the Safari requirements.
Update: Well, I guess nothing is cast in concrete. I will be tackling the R22 tach conversion and I've physically got several of them to work on. While I would have preferred to get the ones from a Beta II with the tighter green range, they're actually pre-Beta II's with the wider green range. I have now figured out how to do a simple recalibration for use in the Safari without having to do physical modifications and they work quite well. I was going to offer these for sale to other builders, but I've also come to an interesting realization ... the reason that many of these tachs are available on the used market is that they come from ships that were parted out and the reason they were parted out is due to crashes. Another reason for their availability is due to upgrades to the newer version with the narrower green band. Of the five tachs I have, two appear to work fine, one is slightly sticky (now fixed), one is quite sticky off the lower stop and one has intermittent operation on the engine side (I refuse to use or sell this one). This is not a very good ratio and I don't think other builders are interested in spending $710 to first have them overhauled. While I still intend to use one of these tachs, I'm not actively looking for more of them or to act as a supplier.
In addition to the R22 tach option, I've got also got another type of tach whereby the dual needles lay on top of each other on a circular scale. The biggest hurdle with this one seems to be to get the proper tach generators and then calibrate it. I have obtained several generators from a Beech that screws into the standard Lycoming / CHR transmission boss and now need to perform additional testing. Once I've got more details on the various options I'm testing, I'll post the results. In the meantime, I'm wiring all my tach related inputs/outputs to a plug within the instrument pod so that different styles of tachs can be exchanged with a simple bolt and plug sequence without any wiring changes.
One potential problem with electronic tachs is that they require an electrical source in order to operate. Before implementing any tach of this kind, I would look carefully at possibly adding a small backup battery, or other wiring changes, for its usage in the event of a total electrical failure. It's also noteworthy that the R22 electrical circuits actually disconnect the electrical source to the tach while the starter is engaged. Unfortunately, the digital Rotor-Tach Alarm has an initialization sequence that would occur post startup if it were wired this way. My first-round implementation of this backup is to use a guarded switch which supplies alternate power to the tach directly from the main battery (well through a breaker). Sure it's a compromise, but the odds of the main battery going below six volts (three+ dead cells) in flight are extremely low ... note that I'm also using an ANL (fuse) that should disconnect everything else from the battery in the event of a major short.
Rotor Alarms / Horns
My kit also came with a high/low rotor alarm system and two distinctive horns but minimal documentation. There are two different versions of this system available from CHR; a P-lead pickup model and an amplified magnetic pickup model that can be attached to the main rotor shaft. The version I received was the P-lead model which has the downside that it tracks engine RPM, not Rotor RPM. Thus this system will not work effectively in an engine-out situation, a practice auto-rotation and in general will fail to operate accurately any time the sprag is not "locked". I have a real concern that since this system does not track true Rotor RPM it won't be available when needed the most and can also generate false alarms which can possibly lead to a conditioned reflex of ignoring them. As a result, I cannot endorse using this device when connected to a P-lead since it can give false indications of rotor speed.
I was led to believe that the lower/upper trigger points are at 460 and 500 RRPM ... testing on my unit confirms that it has a 2 RRPM deadband centered at 460 and 502 RRPM (going high it trips at 503 and resets when below 501; going low it trips at 459 and resets when it gets above 461). Due to the test equipment I used, I was not able to determine it's lower cutout capabilities for the warm-up situation. Personally, I feel that the low speed setting might be just a little low (perhaps 465 would be better) and that the high alarm is set too low (perhaps 510+). Since top-of-the-green is 500 RRPM, the high horn will come on pretty well as soon as one exceeds the green range but certain flight conditions can cause a very temporary slight excursion. I assume that CHR chose these limits due to the fact that they do not offer a governor system as an option. By having the horn set so close, it can occassionaly beep when not appropriate ... my experience with process control alarms is that nuisance alarms should always be avoided since they create a conditioned reflex of ignoring them ... I want my reflex to be that whenever a horn goes off, I need to immediately take action. My biggest fear would be that a relatively low-time pilot might be slow to react to a low horn and thus get into a catastrophic blade stall condition.
As provided, this system is hardwired to just the horns and does not have an interface to an intercom or headphones and I'm aware that one builder had problems hearing the horns with ANR-style headphones. As an alternative, although I haven't physically seen or used these units, I have talked to the developer and it would appear that they have alleviated many of the shortcomings of the CHR-supplied rotor alarm kit. In addition to having an interface for the headphones, I believe this unit also has adjustable high and low trigger points. Another alternative for tones in the headset is the AL-1A Tone Annunciator from Vx Aviation. This unit should interface to the CHR-supplied Tach Tone module and generate tones that can be routed to an aux input on either an intercom or radio.
I have no documentation for the magnetic pickup model other than the electrical diagram and thus I'm unsure whether the pickup is mounted on the main rotor shaft (RRPM) or on the tail rotor drive (ERPM). I quickly tested this input at 2 and 4 times engine speed and it failed to operate properly. Thus I really don't know if it's calibrated for a 1 per engine or ? times rotor input.
I have LASAR® mags and it would appear from the Unison documentation that the P-lead signals from these mags or from vent hole sensors on them are not the same frequency as from conventional mags. The LASAR® controller does provide a tach signal (brown wire) but it should be noted that this signal is not available if the LASAR® controller is switched off and the mags are running in backup mode. From my testing, it would appear that this tach signal should be directly useable if it is wired into the module's P-lead input which is labelled on the wire as "P LEAD / ELECT IGN" even though there is no reference to "ELECT IGN" on the supplied wiring diagram. I'm choosing to mount a separate gear tooth sensor on the tail rotor drive that will be connected to the module's P-lead input and power for it will be from the same source as the horn module ... thus the horns should be available regardless of LASAR® settings.
Note that if one is using the new "digital Rotor-Tach Alarm" from CHR, it has the alarm system built into it and the old style of alarm module is not required. However, installing this combination of new/old does give some redundancy in the event that either unit were to fail.
I have had feedback from one builder who was
trying to track down noise in his radio and detected that the
alarm horn module was one source of emissions. This is very
probable since the module requires a frequency generator /
comparator of some kind and my unit was just housed in a plastic
box ... I think one should be careful about what wires run close
to this box. I'm also surprised that the supplied wiring harness
used shielded wire for the power supply. While this is necessary
for the P-lead (and should have also been used for the tach
sensor input), it makes me wonder whether this device is a
transmitter or just overly sensitive to receiving outside EMI/RFI.
Update: I thought about changing the plastic box to a metal box but the builder of these modules chose to glue them shut and this would have required me to destroy the box and make it a one off that couldn't be swapped out. Instead, I chose to make a cover from K&S #254 Easy Solder Tin that should act as a shielding layer ... not the ideal solution, but I had this material on hand and it is very easy to work with.
In addition to the horn modules that CHR
supplied, I also have a few piezo sounders available in my parts
bin. I set them up on the bench to compare them and figure out
which ones to use. Although I would have preferred a steady tone
version for the low horn, I found that one of the dual frequency
units actually seemed to give a higher pressure level and was
better at grabbing my attention. In the end, I selected the small
CHR unit (273-079) as my low horn and the larger CHR unit (273-070)
as my high horn.
Update: During the initial testing of the wiring in my machine it didn't seem like the low horn was as loud as it appeared to be on the bench. I had chosen to mount the horns under the pilot's seat and soon after this testing I had the headboard off for a different wiring issue. While the headboard was off, I chose to install a Kingstate KPE650SA constant tone sounder into the headboard just below the headphone jacks. Further testing will determine which sounder remains connected for the low horn.
I'm also thinking that I'm going to have to seriously consider changing the MPH airspeed indicator for one calibrated in knots before installation. This would ease both the cross-country planning and map reading as well as making it easier to move back and forth between other machines such as the R22. While I'm comfortable using either KPH or MPH in a car, I'm more used to using knots in aircraft. Another alternative would be to replace the instrument with one that has the dual MPH and knots scales.
The supplied Falcon MP gauge has a 180° sweep for the range of 10" to 35" and it also has large tacky lettering. After looking at a few alternatives, it would appear that the UMA MP gauges have nearly a full sweep for the same range which gives a larger (and more accurate) reading in the useable regions. I'm not sure if I'll change this gauge, but it's certainly something that is in the back of my mind. Unfortunately UMA's website doesn't have a picture of their 3-1/8" 10-35" MP gauge, but I did find this picture of one of their 2-1/4" units:
Sheet #45 of the Construction Prints shows the static port as just being an open end of a Tee fitting at the top of the run. It's my understanding that if one was to use this kind of simple arrangement then you'd actually leave the open end at the bottom to allow any condensation to drip out of the tube rather than into an instrument. Since the climate around here will dictate the need for cabin heat, I'm not sure how the final implementation will effect a static port in the instrument pod due to a possible slight cabin pressure increase. Right now this is just an issue that I'm aware of and will make a decision later on whether to use a more conventional static pressure source such as on both sides of switch panel console or on both sides of the craft. Also, it should be noted that when doing a transponder/encoder check/calibration it will be necessary to access the static line.
Until I hear feedback from someone who has used conventional exterior static ports, I'm not ready to experiment with these. I have read that various Rotorway ships have had calibration errors unless their exterior static ports were positioned in very precise locations. For now, I'm running the 1/4" static line into the area under the floorboard and just leaving the end open. This area should be relatively static and not affected by any fans in the instrument pod. The end of this line is also relatively easy to access for an encoder check since I only have to remove the switch console side panel and not the instrument panel. For reference ... in the R22 the static line is just an open tube within the shroud behind the transmission.
There are two common types of tubing that are used on pitot and static lines: nylo-seal and tygon tubing. The main difference is that nylo-seal uses a relatively rigid nylon tubing and bulky fittings while tygon tubing is quite flexible and uses barbed push-on fittings. Since it's much easier to route, I chose to use tygon for my pitot, static and the MP line once it entered the cabin. The downside of tygon is that it's more expensive and one has to be a bit careful not to allow it to be crushed in it's routing. There is now a third alternative which uses a relatively hard nylon or polyurethane tubing and push-on connectors. Given the ease of use of these new fittings, I would seriously consider using them if I was re-doing this work. A good source of them is Steinair or SafeAir and they're also available from Princess Auto but I don't know if they're the same quality. McMaster Carr also has these as "Push-to-Connect Tube Fittings" but their are different levels of quality ... DOT is probably the minimum. I've seen reference that Parker is the best brand and Norgren is also good ... SMC are cheaper and a good value.
Random thought: I'm aware that various regions have problems with mud daubers, mason bees and various other insects that like to make nests in small tubes. While it is common to see pitot covers to prevent this kind of problem when not flying, I've never seen a solution for static lines other than the use of very small ports. Perhaps a trip to the aviation department at the local pet store will turn up an appropriate aquarium air stone that will prevent insect issues.
Update: There is a Safari that has used convential dual static ports ... one on each side mounted about 3" or 4" ahead of the firewall and about the same distance above the seat bottoms. According to the owner, his instruments are quite steady and his airspeed closely matches his GPS. Sounds like a good solution for anyone who is having instrument errors that may be related to the static system.
Fuel Gauges and Probes
One of the supplied quad gauges has two fuel
level indicators for the left/right tanks ... hopefully with the
cross-feed they should be relatively close to each other. The
supplied probes are of the type that have both high/low
adjustments and also an adjustable low-level warning trigger.
While I still have available panel indicators, I'm planning on
using both low-level outputs, one to indicate LOW fuel and the
other to indicate CRITICAL LOW fuel. I'm not sure at this time
exactly where I'll set them, but probably somewhere around 30
minutes and 10 minutes.
Update: I set my left alarm indicator (red) with 1-1/2 gallons in the tanks (approximately 10 minutes) and the right alarm indication with 5 gallons (just over 30 minutes).
One thing I've always hated about automotive fuel
gauges is that they never seem to be linear and the one in my
Jeep seems to go down much quicker on the bottom 1/2 of the tank
due to its shape. With the round Safari tanks and linear probes,
I'd suspect that the fuel gauges are only accurate at full, 1/2
and empty. It would appear that Pillar Point Avionics
has a solution for this with their probes / control unit that can
be calibrated at up to 21 points. Alternatively, project #273 for
me might be to develop an embedded controller which performs the
linearization function. Princeton
makes a cpacitive probe with 5 calibration points (full, 3/4, 1/2,
1/4, empty) which should also help with the non-linearity issue
... unfortunately I can find very little documentation on these
probes and it appears one would lose the low level alarm trigger
that comes on the CHR-supplied probes.
Update: Perhaps I need to learn how to read again and so does the avionics-trained tech who assisted me with the calibration. The probes were calibrated according to the documentation ... note that they are unbelievably sensitive to any pressure / movement of the adjustment screws. Interestingly when I added 5 gallons of fuel to the tanks, the left gauge reads about 1/4 full (a little high but probably valid due to the tank shape) while the right gauge reads 1/2 full (way too high). And people wonder why I've never been a fan of Westach products.
Thought: The fuel probes have adjustments that
need to be calibrated for full, empty and the alarm point. The
instructions talk about emptying the tanks, filling them, re-emptying
them, etc. to perform this sequence. I see no reason why a piece
of 1" capped tubing couldn't be used for this. The empty
position is just free air and if the tube was filled with fuel
then the probe can be immersed in it to the same level as it
would be in a full tank ... should be a lot easier to work with
less than a pint of fuel rather than 14 gallons. The alarm
setpoint can then be set during the first fueling. Note that this
calibration should be done with the same fuel type as will be
used in operation ... 100LL will require a different calibration
Update: The small tube of fuel technique seemed to work fine and sure is MUCH easier than filling the tanks before it's required.
Supplied with the Safari kit is an internally lit
Falcon vertical card compass and most builders tend to mount it
on the top of their instrument pod. I have heard of at least four
builders having problems with this compass (i.e. failures).
Personally, I wish that CHR had chosen to pay a little bit more
for a PAI-700 compass which
is a TSO'd unit and used in many different aircraft including
Robbies ... with what I know now, I would have had CHR leave the
Falcon compass out of the instrument kit and claimed a credit.
Whether the failures of the Falcon compasses are due to vibration
or as a result of mounting it too close to electrical components
such as the tach is not clear ... regardless, a high percentage
of them are failing by about 100 hours of use in a Safari. It's
also interesting to note that Aircraft Spruce does not appear to
be carrying the Falcon vertical card compass any longer ... makes
me wonder whether they were also having problems with them.
Update: My Falcon compass failed within the first 5 minutes of starting up the engine!!! Looks like I'm joining the ranks of other builders who need to replace it with something that is actually useable and reliable.
Update 2: I decided to change my compass to a PAI-700 and send the Falcon one in for service. Once I get the repaired compass back I'll put it up for sale on eBay. Although this compass was well out of warranty, Wultrad Inc. (Falcon service) chose to just charge me for the parts and not the labor. Regardless, the total cost of the repair and shipping (~$125) will probably be about the same as what I'll be able to sell it for.
Update 3: I now have about 5 hours on the craft using the PAI-700 compass and so far everything is fine. Due to the double change, I'm not sure if this is due to the higher quality compass or the use of MuMetal around the tach and under the top of the console.
As I remember (I need to check), the installation
instructions for the compass specify a minimum of 12" from
electrical components or ferrous materials. This distance is
difficult to obtain if the supplied tach is mounted near the top
of the instrument pod. Some of the alternate tachs use a metal
case instead of "plastic" and I don't believe this
would be as much of an issue with them. One possible solution is
to use magnetic shielding material to either create a base plate
under the compass or possibly to wrap around an electrical
instrument like the tach. This material is manufactured by
companies such as Magnetic
Update: I have now wrapped my tach in MuMetal and also added a layer of the same metal into the top of my console pod.
Once the craft is completed, it will be necessary to "swing" the compass while using the compensation screws to try minimize any errors. A deviation card will then need to be prepared. Technically this is supposed to be done with the engine running and everything powered up and ready for flight. However, I am aware that this is often done just with everything powered up, but without the engine running. Also note for Canadian craft that the compass must be recalibrated every 12 months per CAR 625(C).
The Canadian regulations [ 602.60(1)(d) ] require a reliable "timepiece". While I've seen some very simple arrangements to meet this requirement, I chose to get a Davtron M800 clock as it is simple to use and also has both GMT (i.e. UCT) and an elapsed timer that can be used for cool-down. Note that its not very obvious from their brochure, but there is an optional model with a AA battery backup which allows for up to two years of backup without being connected to the aircraft's battery. I don't intend to wire the alarm function and the power line will be fed from the instrument breaker rather than directly from the battery bus. In fact, I was hoping to not have any requirements for "always on" power and the clock's AA battery will be replaced on the same cycle as the ELT battery.
For those that like to tinker with electronics, Jim Weir had an article in Kitplanes magazine about how to construct your own clock. I'm not sure if all the parts are still available, but the article is available here.
A 10 degree ball-type bank indicator is included with the instrument kit and is normally mounted on the panel. I will also be mounting a classic yarn "string" indicator on the bubble as it is much more sensitive. The string is also extremely effective at displaying cross-wind conditions during the final part of a landing, especially in the mountains. I'm not sure of the exact location yet but would welcome any feedback about placement and mounting method by someone who has already done this.
Trivia: The yarn indicator is on the Minimum Equipment List (MEL) for the R22 and R44. Technically, those craft cannot be flown without the string.
One of the CHR supplied gauges has an Amp meter in it but there is no volt meter to warn of over/under voltage. This can be handy to see the state of the battery before startup and also as an indicator of alternator problems. When I changed my CHT gauge, I got a version that included a voltage measuring option in it. For those that are looking for a very simple solution for a low voltage "Idiot Light", there is a version here that should be simple to install and work fine.
Attitude Indicator, Directional Gyro, Turn Coordinator, EFIS
In Canada, part of the training and flight test requirements, even for a private license, include basic instrument time and capabilities. In addition to the normal VFR instruments, this requires more instrumentation. Night flying requires an additional rating and is not a requirement at either the private or commercial level. However, it does require the ship to be equipped with a "turn and slip indicator or turn coordinator" and "a stabilized magnetic direction indicator or a gyroscopic direction indicator". VFR Over-The-Top requires an additional rating plus the night instrumentation and an attitude indicator and pitot de-ice. It would appear that the only real requirement for IFR equipment beyond VFR OTT is the addition of an alternate static pressure source and duplicated radio navigation devices.
The cost of this additional instrumentation can add up quickly as non-TSO'd electric AI's and DG's start at about $1,000 each and a turn coordinator is $300+. These instruments also seem to be prone to problems and I would have serious reservations about getting used ones unless I knew both the owner and the exact history.
Although these are a luxury, I wanted to leave space in my panel in case I ever decided to add these instruments for training or actual usage. Three large instruments are a lot of panel space and expense, so I started looking at alternatives. The units that immediately came to mind are the new small EFIS units that integrate all of the above plus airspeed, altitude etc. in one display which is driven by solid state electronics rather than gyros.
At the time I was planning my panel, I identified two EFIS units that appeared to have the features I wanted plus a reasonable price (well, relatively speaking). One was the Blue Mountain EFIS/Lite for which I downloaded the various documents and carefully read them. I also had access to an aircraft at the hangar which had one of these units installed. Unfortunately I also got to witness a lot of problems with the calibration of this unit and the difficulties that a licensed avionics technician was having with it ... I was not impressed and decided against this unit. In all fairness, it is my understanding that there is now a new generation of these units available and I have no personal experience with them or even feedback from others.
The other unit I identified as being viable was the Dynon EFIS-D10[A]. This unit is slightly smaller heightwise than the Blue Mountain unit and had all the features, plus more, that I was looking for. I also had access to a plane/owner who had one of these units installed as a backup to a full-blown Chelton glass cockpit. I only heard very positive things about the Dynon unit and in fact the company that I rent hangar space from has now become a dealer for them. Thus the decision on which unit to consider installing was made.
At this time I have not purchased an actual EFIS-D10A since this is a luxury item that I can install at a later time. I do have access to physical units to verify their size. What I have done is to provide the space and cutouts in my panel to mount the actual unit and also to pre-wire for its installation. Splicing of the pitot and static lines won't occur until a physical unit is permanently installed. There are two mounting options; as a protruding display or as a recessed almost flush display. I've chosen the recessed mount. Whether the internal magnetometer is accurate enough or whether an external unit (~$100) is required can only be determined after actual installation and testing. The cost to allow for this simple future installation was ~$20 for the mounting bracket, a D-Sub connector, some wire and breakers. The actual purchase price of ~$2,200 is deferred until I actually feel it is warranted.
I am in contact with one builder who has installed the EFIS-D10A in a Safari and this was done primarily to provide the required instrumentation for instrument training. He chose to install his unit on top of the instrument pod and without the optional external magnetometer. It appears to work very well and both he and his instructor are very happy with the unit.
Note that the EFIS-D10A requires both a power source (preferably a separate breaker) and optionally both a backup power supply and a keep-alive power supply. There is also an option for a 6 ounce internal backup battery which is probably just extra weight for my panel unless I truly plan on VFR OTT or IFR. The backup power supply input is for use where the craft has a backup power supply bus for such critical items as all-electronic ignition and/or only glass panels, while the keep-alive power is to maintain the internal clock and optionally keep the internal battery charged. I'm wiring the keep-alive power to a separate breaker which goes directly to the main battery input on the solenoid board and not connecting the backup power supply.
There is a software update for the Dynon units that now allow either the "traditional" EFIS display or as a HSI and the HSI view can now receive inputs from either a Garmin SL30 Nav/Comm or from a GPS unit that outputs a compatible data stream.
The small EFIS units certainly address all the requirements that might be required for night VFR or OTT flying. There is also another alternative that is about 1/2 the price (or about the price of just the cheapest AI or DG). This is the solid state ADI from TruTrak Flight Systems. Basically one gets a solid state AI, a solid state DG, bank angle and a slip ball for $1095 (plus $150 for internal GPS) at the time of this writing. Seems like a good bargain from a very reputable company when compared to separate gyro instruments. If I were to rebuild my panel, I would consider using either primarily an EFIS system or just steam gauges plus this ADI.
Radical Instrumentation Thoughts
If I was re-ordering my Safari kit and starting fresh on the instrument panel then I would not go with the standard CHR Instrument Kit with the "steam gauges". While the kit does use the traditional instruments and provides pretty well everything one needs, they also take up a lot of panel space and mostly relies on visual scans to detect abnormal conditions. The quality and choice of gauges also leaves something to be desired. If one is trying to do instrument training or flying then you also need to add an attitude indicator, a directional gyro and a turn coordinator; another three large and expensive instruments which are not known for their long-term reliability. In order to save the complexity of a vacuum pump and it's related support equipment, these would need to be the even more expensive electric versions.
The new "glass" displays have become much more affordable and offer a lot of features packed into a relatively small area. They are available in various styles of Primary Flight Displays (PFD's) and engine displays with some versions actually combining the two. Most of them are configurable for what data is actually displayed and offer configurable visual and/or audible alarm warnings. The downside is that each of these units takes a bit of getting used to and one has to be extra careful to create a reliable electrical supply system. In the event that one of these displays needs repair then the craft is grounded. Another potential concern is that some of these displays can pack a lot of information into a very small area which means that instead of a quick scan, one needs to carefully look at them to gather detailed information. However, this is mitigated by the fact that most of them use colour to convey information (i.e. green is okay, yellow is a warning and red is abnormal).
So what would a glass panel like this look like? How about:
A vertical card magnetic compass to satisfy the legal requirements
A dual engine/rotor tach both for convention and as the only truly critical instrument. This provides backup and I'm aware of only one affordable EFIS system with a dual tach arrangement.
If one is taking the backup mode seriously, then possibly also an ASI since rotor speed and airspeed are the two important gauges during autorotation. The ASI allows one to stay in the sweet spot or stretch the glide.
A Dynon EFIS-D100 large screen display as the primary display
A Dynon EMS-D10 display for engine monitoring (or a D120 for those of us that require reading glasses)
Simple, clean and relatively inexpensive (at least in aviation terms) at just over $5,000 for the displays, probes and wiring. With the compass, tach and ASI, under $6,000. Want to make it even more compact and about $1,000 less expensive ... substitute the Dynon FlightDEK-D180 for the above two displays.
The more expensive EFIS systems add features such as moving map, terrain etc. These are nice features, especially for fixed-wings, but I believe they're overkill in a VFR helicopter. If one is doing any amount of cross-country flying or working around various controlled airspaces, then it is nice to have a GPS unit, especially one with a moving map. Continuing on the theme of a glass cockpit, how about a large moving map GPS system such as the King KMD-150 which can be found for under 1/2 of the list price. Adding a radio, transponder and intercom rounds out the whole instrumentation and avionics package. Ironically, I did a quick mock-up of this and discovered that with the FlightDEK-D180 and KMD-150 this panel would be exactly the same height as my current panel, albeit considerably narrower ... about 7-5/8" wide. Substituting a Garmin panel-style GPS would cut 2" off the height and removing the GPS altogether would cut off 4". This was assuming that a small intercom such as the XCOM unit would be mounted in the switch panel rather than the instrument panel. Of course, there is more than enough room to substitute a "round" radio and transponder which would then allow room in the instrument panel for the intercom. Lots of options are available, but some of them reduce the available features.
It looks like I'm not the only one who has looked into using a glass panel. While digging around on the internet, I came across this picture of the panel of D-HEDV. I'm not sure what the lower display is, but I assume it's some form of engine monitoring system.
For those that like to tinker and truly have
unique one-off systems, I ran across a link for an EFIS system
that seems to meet the bill. MGL Avionics have a glass system
called the Enigma
that allows for full customization of what is actually displayed,
whether that be flight instruments, engine instruments, terrain,
etc. It is up to the user to configure the actual displays and in
fact they can design and create totally unique display elements.
It would appear that there is quite a production backlog but that
the system would create the ultimate tinkerer's delight.
Update: It looks like Rotorway has started to do some serious R&D. At Heli-Expo '07 they showed an Exec 162FG ship that had a different skid arrangement and also an Enigma EFIS/EMS system ... supposedly this is a new option that will be available directly from the factory when ordering the kit. It is also the unit that will be supplied on the new Rotorway Talon A600. Interesting that they chose the same two steam gauges that I show in the panel mockups above ... hmmm, I wonder if someone there is viewing this site?
It's also interesting to note that the AK1-3 Ptarmigan Helicopter is going to be delivered with a glass engine monitoring system (ShipShape™). These glass systems are definitely the wave of the future but only after they have proven reliablility since all monitoring is located in a single point of potential failure. With a reliance on the electrical supply, one needs to carefully consider the implementation of the electrical system and backup power options. Also note that the use of a glass display requires that the manufacturer's website be regularly monitored for software updates and information regarding potential problems.
*** WARNING *** If the reader is actually building/flying a Safari, then STOP RIGHT NOW & GET YOUR "TO-DO" or "TO-CHECK" LIST. I strongly believe that there is a SERIOUS fire/explosion hazard that I have not seen mentioned in any of the product literature.
As shown, the fuel tanks are mounted on a rubber pad and held in place by metal bands with rubber anti-chafe molding while the fuel lines are of the reinforced rubber type. There is NO ELECTRICAL BOND shown for the tanks other than potentially the dielectric of any fuel in the lines. As far as I know, this is against all aviation practices and must be rectified by running a bonding wire from the tanks to the frame. One easy way of doing this may be to use a ring terminal under the head of one (or more) of the fuel sender bolts on each tank and running these wires to a good ground location on the frame.
I am aware of several builders who have had major electrical issues and that is why I've added a lot of words on this site about this subject. I firmly believe that it's much easier to do the wiring properly the first time and not have to deal with this kind of aggrevation, expense and delays while trying to sort out a new machine. In the cases I'm aware of, I also believe that a large part of the problems stem from the electrical components and wiring diagram that were supplied with the kit. I do NOT believe that a P&B W31 switch / breaker is appropriate for use as a master switch ... the ones I've seen are much too sensitive and unreliable for this critical application.
Another issue I have is with the master / alternator switch interaction. It should not be possible to have the alternator providing power while the master switch is turned off as this can produce electrical spikes and an over-voltage condition. This configuration is NOT normal aviation practice and should have some form of mechanical or electrical lockout to prevent this situation.
Crimp On Terminal Lugs
AC43.13-1B (11-178) is very clear on these: "The crimp on terminal lugs and splices must be installed using a high quality ratchet-type crimping tool". (11-178a) "... These tools crimp the barrel to the conductor, and simultaneously from the insulation support to the wire insulation".
The terminals on my pre-wired solenoid board appeared to have been done with standard automotive-style crimpers and/or a single lengthwise compression as is normally done on larger lugs. Thus I feel they are in non-conformance and must be replaced or as a minimum re-crimped ... I replaced all of the factory crimps. I chose to get an Eclipse Lunar ratchet-type double crimper from Terminal Town ($38.76); they may not be quite as fancy (or expensive) as some of the other brands, but they appear to do a good job.
I'm not wild about the idea of using Lexan as the foundation for the solenoid board assembly and have never seen this used in an industrial application except as a shield to prevent inadvertent contact. Since contactors are known to get quite warm during use and they are mounted under the board, I don't know what effect this will have especially during cold-weather operations. Bob Nuckolls did some testing on master contactors which showed a 170°F case temperature after two hours of continuous operation at room temperature. Lexan also has incompatibilities with certain chemicals such as ammonia that is used in some cleaners and which can cause Lexan to craze or shatter. Also, the holes on my board were not chamfered and this could possibly lead to stress cracks. I was looking for some 1/8" FR4 printed circuit board material, but this was not readily available so as an alternative, I ordered some 1/8" phenolic board that is available from Aircraft Spruce, Wicks, etc.
The master contactor on my board is the type where the case is actually connected to one side of the coil. In something like an automotive application the case would be grounded and the control terminal would receive a positive voltage to close the contacts. On the supplied board, the control terminal is directly wired to the battery positive and the contactor case has the wire which leads to the master switch/breaker, the other side of which is grounded. While this will work, it also means that if one was to accidentally short the case (or mounting bolts) to ground then the contacts would be closed REGARDLESS of the master switch position. In addition to 4-terminal contactors, there is another type of 3-terminal contactor normally used in aviation (such as supplied by Aircraft Spruce) where the case is isolated and one side of the coil is internally connected to the battery terminal; thus the control terminal is connected to ground via a switch to close the contacts. As a safety precaution I will be changing the supplied master contactor to the type with an isolated case and using an insulating boot over the control terminal.
If one is re-wiring a solenoid board, a possible
alternative to using the difficult #2 gauge wire is to use a
solid copper bar with appropriate insulation such as heatshrink
tubing. I need to double check it, but I seem to remember that a
1/8" x something like 5/8" bar has more area than #2
wire and/or the 5/16" studs on the contactors. These were
definitely easier to work with on my board for short runs where
there would have been essentially two lugs with very little
exposed wire if I'd gone that route.
Tip: One problem with bare copper is that it oxidizes over time and this can also transfer to the mating surfaces. Once I've formed the bus bars, I then clean them up and use a product called Liquid Tin to plate them with a very thin barrier coat which prevents oxidation.
My personal experience has not been great with the kind of terminal strip that was supplied on the solenoid board and I also don't like to make a daisy chain bus from individual wires since there's too many points of potential failure. There were also a couple of wires that had not been properly installed and had a strand or two of wire sticking out. While a normal barrier strip could be used and allows for the use of a single piece of metal for a bus bar, I got some MS27212 bus bars and covers. Although it probably wasn't required, I changed the .047 x .35" metal bars to 1/8" x .4" copper.
The solenoid board came with a voltage regulator and ONE side of a connector. Unfortunately this critical device is not marked as to its origins and I would not feel comfortable using it without further investigation.
AN3 bolts were used by CHR to hold down the contactors and most sides had AN960-10L washers (some were omitted) . The actual holes/slots in the contactor feet are for 1/4" bolts and the combination of 3/16" bolts and thin washers resulted in washers that barely caught the edges of the contactor feet and were severely deformed. I believe that either AN970-3 large washers should be used or the bolts/washers changed to AN4 series.
The terminal lugs that were attached to the #2 wire on my CHR-supplied solenoid board had a 3/8" hole rather than the required 5/16" hole and thus had some slop. Most of the wire strands at the outside of the cable had been nicked when the insulation was removed and at least a dozen strands fell out when I removed one of the terminals. Needless to say, I've changed all the supplied terminal lugs.
Relays (i.e. solenoids / contactors) can produce a very large electrical spike when they're switched; especially off. The use of a 1N540* (*=4,6,7 or 8) diode will avoid the arcing/pitting of the switch contacts and help prevent a possible negative transient from getting onto the electrical bus. Various diagrams on www.aeroelectric.com show the proper use of these and they're both cheap (under 50 cents each) and readily available at most electronic shops. A convenient way to mount them is to solder or crimp a ring terminal on each end and use heat shrink tubing over the whole assembly; remember to clearly mark which is the banded end if you're not using clear tubing.
Tip: If I have "fuzz" edges after cutting, drilling or sanding phenolic or PCB material, I've found that a LIGHT coat of thin cyanoacrylate glue will quickly seal it and actually reinforce the edge. Holes will need to be resized if they're treated this way.
In order to keep electrical noise to a minimum, I chose to use just one main ground bus. Since a lot of the requirements were in the instrument panel plus some were in the bay under the seat, I placed this under the switch panel. While this does sort of average out the wire runs, I now believe this was a big mistake ... not electrically, but physically. The area under the switch panel is quite confined and since I have a lot of breakers on the panel, the real issue becomes one of maintenance and future access to screw terminals. Once all the wiring is in place, it's really awkward to access this area.
If I was doing this again, I'd make my solenoid board a bit wider and add the main ground bus onto it where there is easy access for maintenance. I'd probably add a small secondary terminal strip within the instrument pod that would be connected back to the main ground bus by a heavy wire and only used for the radios, the intercom and their associated shielding. Perhaps another small terminal strip for instrument grounding, but again wired back to the main ground bus and not the radio ground bus.
Hindsight is wonderful, but this would be a big change for me right now. This problem is a direct result of trying to drill the holes for the bus bar before painting the switch console rather than waiting until the console was physically installed and then planning the various wiring runs.
External Power Plug
The supplied frame has a mounting tab for an external power plug and it is up to the builder to decide if they want to cut the matching hole in the firewall rib and install the plug. Due to the climate I live in (lots of cold weather), I chose to install it even though it probably cost me 2˝ pounds or so. One of the problems I found with using the Cole Hersee "Piper" power receptacle was that the hole for the wire is much too large for just soldering in #2 wire. I chose to turn a brass collar (~.040" wall) to fill most of the void and then soldered everything together.
In the Spring I found a good deal at the automotive store (i.e. a stock clearing sale) and got a long set of #4 booster cables which were then wired into the plug. Hopefully I'll never need these but they're now available and I'll probably end up using it a bit during the wiring installation and testing.
For those that are using the external power plug, you may want to look at the Aeroelectric website for the article and wiring diagram for one of these that includes both a breaker switch and an Over Voltage Protection (OVP) circuit. While it does have the weight penalty of an extra solenoid, it will prevent any expensive problems from reversed jumper cables or the use of 24V jumpers instead of the required 12V . When wired according to this article, the press-to-test indicator lamp is illuminated when ground power is active and the lamp test feature is used to indicate ground power is available but not selected. One interesting change to this circuit might be the use of a bi-colour LED whereby one colour indicates ground power is connected and the other colour indicates it is active.
I chose to get an Odyssey PC680 battery (without the metal jacket vs. PC680MJ which is slightly heavier and more expensive) instead of using the RG-25XC battery that CHR supplies a certificate for. This battery is about eight pounds lighter, is of the sealed dry type, is designed for cold weather, has a long design life, has deep cycle capability and has a very long storage time. It's used in many of the RV aircraft and Hawker has what appears to be an identical battery that's FAA-PMA approved for use in Piper's PA-18 and PA-19 series. While it's smaller than aviation batteries, I'm still going to use the supplied battery box with appropriate spacers since I can't predict what future batteries may be installed. Also, one should be aware that the Odyssey batteries require either a special charger, such as the Battery Defender [Pro], or VERY careful measurement and timing with a regular charger. The Battery Defender I received from Battery Mart is actually a Soneil 1206S that may be available from other Soneil distributors. Note that there is some good information about charging these batteries on the Odyssey website. They have also now released their own line of specialized battery chargers and they are described here.
In order to keep the battery cables as short as possible, I found it easiest to route one cable over the top of the battery within the battery box. This required a 0.6" dia x 0.28" brass spacer between the battery connector and the cable terminal plus a longer M6 bolt than was supplied with the battery. Battery box sidewall spacers were made of 1" square aluminum tube on each side and the total end spacer requirement is ~3/4". Note that certain other materials can release very toxic gases if they're ever exposed to sulphuric acid from a battery leak. The biggest problem I found with the battery box was with routing the heavy cables and their large bending radius. I could get very short cable runs by exiting the cables along the sides of the battery box, but the ground cable on the outside might interfere with the sheet metal on the seat and the positive cable on the inside could interfere with the cyclic control tube.
Now that things are ready for final installation, I did a double check on the various clearances. The ground cable can exit the the side of the battery box but there is only about 1/8" of vertical clearance to the side panel. I might add a small pad of rubber under the side panel to prevent any chaffing, but this shouldn't be a problem. Note that there is restricted access to the bolt on the frame ground and it is probably easier to install this bolt before the side panel is installed. The positive cable can exit the side of the battery box nearest the solenoid board, but there is only 1-3/4" clearance to the cyclic tube. The # 2 cable can be bent enough to avoid clearance issues but this is one bend that I will be very careful with in order to get maximum clearance.
Aircraft Spruce sells a battery mat (P/N 11-00170) that's like a very dense felt fabric about 3/16" thick and can be used in the bottom of the battery box to provide vibration isolation and a cushion against the screw/bolt heads that hold the battery box to the frame. The real purpose of this material is to act as an acid absorber and neutralizer in the event of a spill. While the builder may not plan on using a spillable battery, it's hard to predict the owner and status of the ship many years down the road. Along the same vein, I was surprised to find that although my epoxy urethane paint is nearly impervious to everything, it is not totally resistant to sulphuric acid. I guess that's why they still sell acid proof battery box paint.
The construction plans don't show it, but there should be a vent tube in the battery box to the exterior in order to eliminate any chance of a hydrogen buildup since even most sealed batteries have a pressure relief vent that can open during very high charge rates. Again, depending on the type of battery that the builder (or any future owner) installs, this could be a serious safety issue. AC43.13.1B(11-22) clearly shows how a vent can be installed. In my case I've machined a couple of barbed nipples for this purpose, but I think some of the pitot static ports that are sold by various aviation suppliers could also work if the hole was drilled larger.
Another alternative for the battery might be the Deka series which are carried by NAPA stores. It's my understanding that some of the Rotorways are now using the Deka ETX 16L which should fit in the original style Safari battery box.
It would appear that the newest Safari kits now mount an Odyssey battery under the floorboard on the right side. I've had some feedback from a builder who changed the old style battery box with the RG-25 battery to the new style. Interestingly, the CofG of the craft did not really change ... the new battery is mounted further forward but due to it's lighter weight the net effect is essentially the same. However, it will be interesting to hear whether this might have changed the location where 2/rev resonance might be occuring.
Odyssey PC680 battery under right side floorboard
Fuses and Breakers
I've now received feedback from a couple of builders about the P&B W31 style toggle breakers that are supplied with the kit. These are extremely convenient as they combine a toggle switch and a breaker into one assembly. However, one builder has had three of these fail mechanically and another builder has found that the heat buildup in the bubble can prevent his from being turned on. I've also found that even on the bench, several of mine are very sensitive in the ON position and can easily be tripped OFF with just the slightest bump. I changed my switch panel to use separate toggle switches and Klixon breakers on all critical circuits as I don't believe the CHR-supplied devices are appropriate in those circuits. Due to limited panel space, I've retained the W31 breakers on the light circuits, but in the back of my mind I'm prepared to figure out how to change these if they don't prove to be reliable.
I am aware that some builders and consultants prefer to use ATO (i.e. automotive) fuses rather than the expensive aviation breakers. Part of their reasoning is that if a breaker or fuse "pops" in flight then it should be investigated before being reset. One of the negatives is that the regulations state that you must carry replacement fuses in flight regardless of whether you plan on trying to replace them. I was recently made aware of a unique ATO fuse that has a built in LED lamp (available here) that illuminates if the fuse blows ... real easy to identify if a fuse has blown. One potential downside is if one is doing night flying and they're positioned in a place where the LED would be visible then it could be distracting.
While the wiring diagram in the provided construction prints will work with the provided solenoid board under many circumstances, I have several issues with it relating to fusing:
The main power distribution bus is on the
solenoid board mounted under the right seat with
individual wires going from there to the breaker switches
mounted on the console. Thus there is approximately 20
feet (~2.5' * qty 8) of unprotected wire in addition to
the short runs on the solenoid board and the long run to
the amp meter. Normal aviation practice is to make a very
short run through the firewall and directly to a bus bar
that feeds the various breakers and fuses ... I have seen
references that state the aviation rule of thumb is a
maximum length of 6" for unprotectect wires. I'm
thinking about moving the distribution bus to a point
just below the breakers on the console side and running a
heavier wire to it from the solenoid board. This heavier
wire will be fuse protected right at the solenoid board.
Although this creates an in-flight unreachable fuse, I
believe that if this fuse blows its a direct result of a
MAJOR electrical problem. Off the top, I can think of
several other alternatives:
- One could just add a fuse on the supplied solenoid board between the shunt and the bus bar.
- If the alternator lead also has a fuse then one could add a fuse between the master solenoid and the shunt.
- Add a fuse to both amp meter leads and also add alternator and bus bar fuses.
These were just my initial ramblings. Since I've chosen to add my wiring diagrams, the details of my solutions are contained therein. The brief description is that I added ANL current limiters to both the master bus and the alternator feed plus added fusible links to the shunt and a few other places.
The alternator is shown wired directly to the shunt without fusing or current limiting. While an 8 gauge wire (or possibly 10ga. or 12ga. depending on alternator; I haven't checked all permutations) will definitely suffice for the ~40 amps that would be produced by the typical alternator used in this installation, the alternator current is not the issue. If the alternator diodes fail it is possible to have a direct short to ground inside the alternator whereby it's the battery that is supplying several hundred amps through the wire to the short! I will definitely be adding a current limiting fuse to the alternator wire.
For those that are using electrical tachs (i.e. ones that require external power and not just the generators), they should seriously look at creating a "critical bus" configuration. This technique is well described in some of the RV newsgroups and also in some of the aviation wiring books. An even better alternative would be to use a dedicated backup battery and some kind of automatic switching circuit that applies power to the tach so long as the rotors are turning above some pre-determined speed i.e. no need to apply during shutdown. One more project to think about once I've completed all the others.
My kit came with 200 feet of 16 gauge, 9 feet of 12 gauge and 7 feet of 2 gauge non-shielded tefzel wire, plus 12 feet of 16 gauge shielded wire for the magneto P-leads. For those that choose to dig through the tables, they will find that for many of the requirements this is much heavier than required and although it causes absolutely no harm, it could be replaced with a lighter more flexible gauge of comparable tefzel wire. I can't imagine trying to solder 16 gauge wire to things like the indicator lights or stick switches ... it's way too heavy and not required. Unfortunately I've now seen how a Safari was wired this way and I'm certainly not impressed.
Since I've had the misfortune to try eliminate RFI/EMI problems in the past (extremely painful), I have chosen to try use shielded cable wherever appropriate in an attempt to eliminate this kind of problem before it ever becomes an issue. With proper routing, some of this could be done with twisted pair wires, but there's still the need to route all the wires in close proximity at the top of the instrument switch panel. The following are some of places I have chosen to use shielded wire/cable:
The kit comes with lighted instruments (some are post lights), navigation lights, a strobe and a landing light. The navigation lights are standard Whelen aviation units and since a landing light is not a requirement in non-commercial operations it does not have to be certified. However, I do have some concerns about the supplied strobe (i.e. anti-collision) light and the wrong tail position light model was supplied with my kit.
I believe the 5 amp switch/breaker that is supplied for the navigation lights is under sized if wired per the construction prints as these three lamps are shown as 2 amps each in the Whelen catalog. Another Whelen document shows the forward position lamps as 1.9 amps each and the tail position lamp as 1.8 amps for a total of 5.6 amps. If the instrument lights are wired as per the POH to the navigation light circuit, then this breaker is definitely overloaded. I'm using a dedicated 7.5 amp switch/breaker for the navigation lights and a separate switch/breaker for the instrument lights.
Since the supplied Falcon gauges (ALT, MP, AS, VSI) are unlighted, the instrument kit contains four Whelen A350-14 post lights. While these work, I am aware that not everyone likes them and they do create significant protrusions on the instrument panel. I have seen various options such as Nulites, which sandwich between the instrument and the panel, and they seem to work very well both for lighting and in creating an illusion of internally-lit instruments. I've chosen to go with the Nulites rather than post lights. As a side benefit, these also make the cutout notch for the altimeter adjustment easier (LW3014AA model) to fabricate as it just requires a semi-circle in the panel rather than an almost oval type shape. Note that the VSI also has a requirement for this special relief. I chose to use a standard LW3014 model for the VSI and just mill a relief for the protrusion and slightly move the adjustment hole inwards. Also note that the Nulites are slightly larger (perhaps 1/16") than most instruments and this might cause problems in very tight panel designs.
When installing the Nulites, after verifying their position I then did the wiring for them and found that it was easiest to remove and re-install the lamp assembly on a couple of them in order to reverse the direction of the leads. Since they're slightly smaller than the 3-1/8" cutouts and allow some movement, I put small dots of silicone on the corners when I was happy with their position. This allowed the instrument to be removed without moving the light ring and it's attached wiring.
I'm not overly impressed with the Westach lights
and how they mount. While the concept is simple, there is a
potential problem if one has to use ganged tubes (the quad gauges
use the long "A" tube plus short "D" tube).
It would appear that the lighting hole in the case is just
drilled in plastic and this can create a very snug fit on the
lighting tube(s). If one tries to remove the tube, such as to
change the bulb, the second tube can get caught and prevent the
removal of the bulb. How do I know ... I did a trial fit and the
bulb and short tube got caught inside the case. One has to be
very careful trying to remedy this otherwise the instrument will
have to be sent back for repair ... I used a combination of an X-acto
knife and a piece of serated tubing to slightly open up the hole
and I finally got the bulb removed. I also have an issue with my
tach which has the dual bulbs ... the single long "A"
tube is too short and the next longer combination is too long. I
decided that using the longer combination with RTV to hold the
back of the post in place would be the best solution. In the end,
I decided to just use a Nulite on the tach since this also gave
the flexibility to change the instrument to a non-lighted one.
Tip: There are wires inside the Westach gauges that can snag on the end of the light post as it is inserted. After the silicone holding the bulb has cured, an X-acto knife can be used to trim a small angle into the square end of the post next to the bulb to prevent this snagging.
No reference is made in any of the CHR manuals about the use of a dimmer circuit for interior lights. While the classic rheostat dimmer would work, there is a mixture of different types of bulbs that may lead to uneven dimming intensity. I'll probably end up home-brewing a multiple-circuit dimmer controlled by a single pot or automatic circuit similar to this one.
Tip: If one is using the CHR supplied post lights then they can be used in place of one of the instrument retaining screws (typically upper left for our application). However, this can cause a maintenance issue if the the instrument ever needs to be removed since the lamp wires will also need to be disconnected. I've seen these post lights installed in their own unique hole just above the instrument and centered on it such that the posts shouldn't need to be removed at the same time as the instrument.
The tail position lamp supplied with my kit was a Whelen A555A-V-14V which is for vertical mounting whereas the tail boom mount is pre-drilled for a Horizontally mounted lamp (i.e. the hood on the lens cover should slightly cover the sides of the lamp). Even one of the factory ships has this wrong part in the picture I have that shows this area. I noticed that Wicks does offer the horizontal retainer as a separate part (# A425A-H) for ~$29 at the time of this writing. It would be a lot easier (and cheaper) for builders if kit manufacturers actually read their supplier's installation instructions and supplied the right parts to begin with.
Wrong orientation (Vertical) for use on the Safari
Proper orientation (Horizontal) for use on the Safari
The tail boom (i.e. frame) is often used for the ground wire on the tail lamp and saves running another wire the full length of the boom. It would have been easier if I'd added a ground stud before mounting the tail rotor gearbox as the best location is under the rear center part of it. Since I didn't, I used one of the lamp's mounting bolts for this. The paint under the washer area was first removed and a star washer was used between the terminal and the frame using lots of DC4 for corrosion protection.
Hard to see from this angle ... it's actually the black wire that goes to the terminal. Silicone tubing and RTV were used to seal the grommet after the picture was taken.
For those that don't know which side the red and green navigation lights go on, every document and aviation regulation I've seen shows the red on the left (i.e. pilot's side) and green on the right. In my opinion, the following craft that's registered to the CHRI President has them reversed and would be illegal for night flight. And yes, I checked to see whether the photo was reversed ... the tail rotor is on the correct side as are the registration marks.
Personally, I wouldn't mount the antenna right next to the strobe light like this ... potential noise interference
The kit supplied strobe lamp is not aviation approved, therefore it would *NOT* be legal for night VFR use in Canada. More importantly, from the data I've gathered it would appear that the supplied strobe is a single flash clear unit with 50 effective candela while the helicopter requirement is for a red unit with a minimum of 150 effective candela (400 effective candela red or white for fixed-wing aircraft). Switching the lens on the supplied strobe from clear to red would further reduce its intensity to only 10 effective candela according to the data sheet!!!
The reason that a red strobe is used on helicopters is to reduce the reflection of the strobe from the blades which can produce vertigo and other nasty side effects. That's also why the underside of the blades on most commercial helicopters are black. I noticed on a factory built craft that they chose to add a reflector inside the lens to prevent light from emitting forward. While this may help prevent blade reflections, it also makes an already too dim strobe even more illegal for night VFR ... the regulations call for 360° degree visibility around a vertical axis and 75° above and below a vertical plane. Although there is a lot of flexibility in experimental / amateur-built aircraft parts, I sincerely wish that CHR would read or ask about the regulatory requirements before choosing parts for the kit and subsequently modifying them. Regardless of the safety issues, this factory built craft is not legal for night VFR flight even though it might appear to be on first glance.
Even for day-only VFR use, I believe the supplied strobe is not bright enough. After having the chance to pass within 500' vertically of another helicopter going the opposite direction and knowing its general location, I've learned how hard it is to spot them in daylight, especially while performing other normal scans. I've now become a firm believer in doing everything possible to be seen early to avoid a near-miss situation. The use of a red lens severely restricts the effective output (to approximately 1/5) so I'm thinking that I'll probably go with the split red/clear lens which allows for maximum side/rearward visibility while reducing forward reflections off the blades etc. I've also been very impressed with the multi-flash units (i.e. Whelen Comet Flash) and how they increase the attention getting factor. While this would be an expensive upgrade, I think that the 10-15 fold increase in effective output would be worth it.
Update: Much as it hurt the back pocket, I broke
down and got what I consider a serious piece of safety equipment.
I got a Whelen
A490A,TS,CF power supply and an A470ADS strobe head (note that
one also requires an H102 mounting adapter and an installation
cable kit). Definitely not a cheap solution to this issue, but I
feel a lot more comfortable knowing that I might be seen more
easily. The power supply is mounted in the cab on the passenger
side just in front of the "firewall". The strobe head
is mounted one "bay" aft of where the factory supplied
strobe is mounted and on the other side of the boom; the reason
being that I'm using the factory supplied strobe mounting plate
for mounting an antenna. The strobe head is extremely lightweight
and only a small mounting plate (~2-1/8" diameter with a 1"
hole in the center) is required so there shouldn't be any weight
and balance issues when moving the strobe rearwards.
Unfortunately, the 3-conductor 16-guage shielded cabling from
Whelen seems quite heavy at a listed weight of 0.05 pounds/foot.
I've found a source for low volumes of Mil 27500 18-guage 3-conductor
tefzel wire, but so far haven't seen one for 16-guage. I'll keep
this option in the back of my mind as I'm looking for various
items, but I'm somewhat reluctant to change the cable without
having looked into the potential RFI issues.
N.B. While Whelen uses 3-conductor 16-gauge cabling, it is interesting to note that Aeroflash recommends 18-gauge cabling.
There are now getting to be some interesting alternatives for position lights and strobes using LEDs (Light Emitting Diodes) which have a very long life and tend to be more rugged. Some of these companies also use the standard flash tubes and are an alternative to the common brands. I haven't personally seen or used any of these units, but here is a link to a sample of one. Note that many of these are still in the "experimental" category and may not be officially approved for night useage.
After taking care of the strobe, navigation and instrument lighting, there is still the issue left about a map light. This can also be used as a backup in the event that there is a failure in the dimmer circuit for the instruments. I found a red map light from an R22 and added it to the top area of my headboard. It's actually wired into the same switch and breaker as the nav lights which means that it would be hard to accidently leave it turned on during most normal operations.
Another builder clued me into a different potential issue. The instruments have their own lighting and the map light can illuminate a lot of the panel. However, there is no convenient way to see the position of the switches and breakers unless some kind of illumination has already been selected. I added a red LED lamp and rocker switch in the area under the center collective. This is wired into the instrument bus and can be used to illuminate the various switches and breakers.
I used a couple of relays (Tyco T9AP5D52-12) for both the hook and as an instrument disconnect during starting ... these were mounted on the solenoid board. I also needed some small relays (DS1E-M-DC12V) for both my governor and trim system. While these could have just been wired inline, I made a small metal box for them which is mounted under the pilot's seat. In the event a relay needs to be checked or replaced, the connector can be undone and the small box moved to the bench for checking. The metal box should also give some shielding to other wires and devices from the magnetics of the relay coils.
Cover not shown in this picture
I was at one of the auto stores recently and noticed that they had a plug that fits the landing light relay. Rather than having four spade connectors to remove if changing this relay (including two with heavy wires), there would only be the single plug. Since my relay is already wired, I'm not making this change.
I'm working on my own version of the wiring diagrams that include both subtle modifications of the CHR provided diagram and also to incorporate all of the avionics and various other unique electrical items that I'm adding. Having worked with electronics for many years, I feel that its very important to both create and maintain these diagrams as they're the only way I know to quickly evaluate a potential problem and/or decide upon modifications. Because I'm familiar with it, I chose to do these diagrams using the Eagle CAD program (limited capability freeware available) and this allows for easily updated diagrams. The one negative is that I had to create a library for many of the unique aviation symbols and devices. If anyone chooses to look at these diagrams and spots a potential problem, I'd sincerely appreciate receiving the feedback so that I can update my diagrams and wiring to avoid potential problems. I've chosen a simple (i.e. relatively quick) way to convert these diagrams to low resolution pictures for the web ... if anyone wants high resolution ones of an individual sheet then I should be able to provide it.
<WIRING 101> Some various thoughts and wiring techniques
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Last updated: September 21, 2011