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Backup Instrumentation

GrayHawk

GrayHawk

Well Known Member
I am thinking of upgrading my early 1990's RV-6A VFR panel from a mix-mash of mostly electrical (no vacuum) discrete gauges; just added when ever & where ever (no organization) to a panel with a little glass in it. I've already gotten rid of an older GPS/Loran system, and may also eliminate the VOR nav.

This is what I am think of for the core functionality:
(AFS EE-3400 & Airmap 2000C)

Glass.jpg


My question is what to keep as backup. Maybe just enough to get down safely. I always carry a portable COMM and a portable GPS; so I am mainly interested in flight and engine backup, and in priority order.

Here are my thoughts:
FLIGHT:
1. Air Speed
2. Altimeter
3. ?

ENGINE:
1. Oil Pressure
2. Oil Temperature
3. Tachometer
4. ?

Thanks for any feedback,
 
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feedback on real world back up

Hi Gray,

I was flying home from S&F sunday afternoon with my 10 yr old son. We were cruising at 14,500 on O2, going fast in very smooth air, and then.... my dynon D10A goes completely black. We smell a faint electrical odor in the cockpit... check amps, check volts, no low voltage, all good. it appears to be coming from the inside of the dynon instrument. fly the rest of the trip on steam gauges ASI, alt, and a Tru trak ADI (even though it was VFR... nice to know it was there.) Land, and check fuses and all wiring... nothing there out of line.

Call Dynon and they are quick to help me out be replacing the instrument with a refurbished unit (I have 230 hrs on the ship). always great custoemr service from Dynon!

My point is the back up is a good idea. My D10a is primary for me but sometimes, for whatever reason, things happen.

hope this helps,

Jeff RV-7A Tiffin OH
 
496 maybe

Hi Gray,
If the 2000 C doesn't have weather capability, I'd sure have to consider a 496. It's an incredibly useful tool to have in the cockpit and even more so at night and IMC.

Regards,
 
I agree with Perry. A 396 or a 496 is a good back up panel system, has in cockpit weather, and tons of other info that can go in your car when you land. I use my 396 several times a week for intown road navigation and speed o readings.
 
I think your list and priorities are spot on.

I would caution however that steam guages are not perfect.

I am kind of a dinosaur and tend not to put great trust in things that are programmable and flat.

I have 2 efis's in my new plane as primary and backup UMA engine guages as well as a backup electric Horizon.

On my 1st XC after phase 1 the Gyro Horizon crapped out and since then 2/3s of my UMA guages have eithe quit or become innacurate. The EFIi have been rock solid.

My gyro horizon was the cheapo not RC allen. All RCA owners I have talked to have had no problems. Everyone who went the cheap route has had trouble. I am going to replace it with a TruTrak ADI. Haven't decided what to do about the UMAs yet.
 
JCN247DE said:
fly the rest of the trip on steam gauges ASI, alt, and a Tru trak ADI
Click to expand...

I chose to back up my dual GRT with the same as Jeff. In addition, I also have a VSI------more to add symmetry to the layout, (and it was a freebie)----I ended up with a pair of round gauges under each of the GRT screens.

In addition, I opted for the built in GPS in the ADI, so that I have heading info, and it is switched as a backup to the GRT's gps to drive the auto pilot.

And I love Milts comment "I am kind of a dinosaur and tend not to put great trust in things that are programmable and flat." Milt and I have a lot in common.

Mike
 
pierre smith said:
Hi Gray,
If the 2000 C doesn't have weather capability, I'd sure have to consider a 496. It's an incredibly useful tool to have in the cockpit and even more so at night and IMC.

Regards,
Click to expand...
I agree. I would really like to have weather. Problem is the Garmin products are too expensive. If I put $2700 into a 496, then I can't afford the AFS 3400/3500. It's a compromise.
 
Does the engine care?

I'd suggest that backup engine instrumentation is not necessary. It would help you re-launch in the event of a failure, but if the goal is simply to get down, who cares? The engine doesn't know if its gauge package is working or not.

As for the steam-gauge thing, I have full backups, too. But they've been the only troublesome instruments in the airplane. The Dynon D100/120 combo has been rock solid, never a peep. But I've replaced the airspeed and VSI twice (once the VSI needle hopped off the peg in flight); the United altimeter has been fine. I've also had the TruTrak ADI in and out of the airplane. The first one went back for a cosmetic problem--pitch bar was scuffing the inside of the glass--but it failed twice more after repair. A second unit also failed. Two of the failures were of the pitch bar.

I've heard the same stories about the Falcon and RC Allen attitude gyros, so is there anyone running one of the Sporty's backup gyros? I wonder if that's a better backup for us.

--Marc
 
Weather

GrayHawk said:
I agree. I would really like to have weather. Problem is the Garmin products are too expensive. If I put $2700 into a 496, then I can't afford the AFS 3400/3500. It's a compromise.
Click to expand...

I talked to both Lowrance and AVMAP at Sun N Fun and they both were "fairly" sure they would be introducing weather this year at OSH.

I too want weather even in my VFR/Night panel and hate to pay Garmins price. Now it's down to compatability with Dynon and Trio. I really like the size of the AVMAP, along with it's features, but haven't had the opportunity to do much research.
 
Different Perspective

Here was my thought process. I'd forget the engine instruments. They aren't needed to get you on the ground. I'd also forget the altimeter. You flying VFR, right? You can see the ground, right? What I would add is an electric AH, like the Castleberry unit that Sporty's sells or one of the TruTrak units that simulate the AH.

If you are going to do much cross country, I'd also add an autopilot. At a minimum, a wing leveller.

I've not had my GRT units fail but what I have done is inadverdently turn them off in flight. Due to my poor switch design, I put my avionics master switch right next to my fuel pump switch. The GRT units don't erect in flight like they are supposed to. Well, after taking off from Key West in the early morning haze out over the water, I switched off my EFIS instead of my fuel pump. My old electric AH was TU (cheap Chinese unit since replaced). I'm glad that I could switch on the AP to level off. Stopped at Marathon and reset the instruments.

My $.02.
 
PaulR said:
I talked to both Lowrance and AVMAP at Sun N Fun and they both were "fairly" sure they would be introducing weather this year at OSH.

I too want weather even in my VFR/Night panel and hate to pay Garmins price. Now it's down to compatability with Dynon and Trio. I really like the size of the AVMAP, along with it's features, but haven't had the opportunity to do much research.
Click to expand...
I am not specifically endorsing Lowrance and am still open to the GPS/Moving Map/Weather functions. I chose the 2000C because I already have it, so no incremental cost. I plan to panel mount it with a gimbal arrangement to let me tilt it slightly and also want to look at extending the SD card slot to the upper part of the gimbal frame.

PS: Backup portable GPS is GPSMAP 196
 
f1rocket said:
Here was my thought process. I'd forget the engine instruments. They aren't needed to get you on the ground. I'd also forget the altimeter. You flying VFR, right? You can see the ground, right? What I would add is an electric AH, like the Castleberry unit that Sporty's sells or one of the TruTrak units that simulate the AH.

If you are going to do much cross country, I'd also add an autopilot. At a minimum, a wing leveller.

I've not had my GRT units fail but what I have done is inadverdently turn them off in flight. Due to my poor switch design, I put my avionics master switch right next to my fuel pump switch. The GRT units don't erect in flight like they are supposed to. Well, after taking off from Key West in the early morning haze out over the water, I switched off my EFIS instead of my fuel pump. My old electric AH was TU (cheap Chinese unit since replaced). I'm glad that I could switch on the AP to level off. Stopped at Marathon and reset the instruments.

My $.02.
Click to expand...
Really GOOD feedback from everyone. Thanks!

I kept the altimeter in the list as it is basically free (I have it in current panel of course) and I fly a lot under class B airspace. I suppose GPS might be good enough.
I do a lot of cross country so yes on AP. It currently has a Naviad but would like to go to solid state gyro.
Current panel has electric AH so I could keep that.
Good point on switch arrangement. I've given some thought on how to arrange switches (all on a lower sub panel).
 
GrayHawk said:
My question is what to keep as backup. Maybe just enough to get down safely. I always carry a portable COMM and a portable GPS; so I am mainly interested in flight and engine backup, and in priority order.

Here are my thoughts:
FLIGHT:
1. Air Speed
2. Altimeter
3. ?

ENGINE:
1. Oil Pressure
2. Oil Temperature
3. Tachometer
4. ?

Thanks for any feedback,
Click to expand...

If I were starting from scratch to your list I would make these changes:

Add a Turn-and-Bank (electric).
skip the engine backup gagues.

But If you already have the other equipment, I would probably only remove as much as I needed to fit the new equipment in.
After all we can't have to many intruments in the panel can we. :rolleyes:

Kent
 
About the Sporty's gyro

I went to Sporty's site to refresh my memory on the cost and found that it's only for sale directly from Castleberry now. Uh-oh, I thought, now that the initial contract is up, they'll jack the price to the moon.

I was pleasantly surprised to see it offered at the same $1995, and you can buy direct from the site.

If I didn't have credit coming from my avionics shop on the ADI, I would have gone this route as a backup attitude indicator.

--Marc
 
kentb said:
But If you already have the other equipment, I would probably only remove as much as I needed to fit the new equipment in.
After all we can't have to many intruments in the panel can we. :rolleyes:

Kent
Click to expand...
The backup instruments would be from the existing panel. The only new instrument would be the AFS 3400/3500 combo unit. Unfortunately I don't have an electric T&B right now.
 
kentb said:
If I were starting from scratch to your list I would make these changes:

Add a Turn-and-Bank (electric).
Click to expand...
The electric TnB has very limited functionality, but it is cheap and could be very a useful instrument if everything else goes dark. Nowhere as expensive as an electric AH. I just wish they made good ones in 2.25" size. The TruTrak unit is nice, but IIRC, it requires GPS input.
 
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KPmarc said:
If I didn't have credit coming from my avionics shop on the ADI, I would have gone this route as a backup attitude indicator.
Click to expand...

Since we're talking about backups to various devices in your panel, please be aware that the ADI from TruTrak is NOT an artificial horizon. It's a VSI and a turn rate indicator. It will show you pitched down when in a stall even though your nose is way above the horizon. It will show you banked when doing a flat turn.

It may be a good backup that can help you get down in an emergency, but please learn about it and use it properly.
 
Good point about the TT unit. Personally, I've never had much use for the T&B. I think the AH is worth the little additional money given the better quality now availabe from the Castleberry unit. The "other" electric AH available is pure junk.

In terms of using stuff because you have it, I would caution you to re-think that. Adding more to the panel adds complexity and can contribute to confusion during an emergency. I had to sit down and think about different failure modes and my resulting actions. I found redundancy was good, but if I could reduce complexity at the same time, that was even better. Here's a picture of my RV-6 panel (second airplane) and then my Rocket (third airplane). You could say "Lesson Learned".
Arizona1.jpg
Panel001.jpg
 
f1rocket said:
In terms of using stuff because you have it, I would caution you to re-think that. Adding more to the panel adds complexity and can contribute to confusion during an emergency. I had to sit down and think about different failure modes and my resulting actions. I found redundancy was good, but if I could reduce complexity at the same time, that was even better.
Click to expand...
I agree, I want to keep the backup stuff to bare minimum. That's why I asked; to develop the bare minimum list.
 
GrayHawk.

Filter all the info, then use what meets your own comfort level.

All the posts here have validity, but they mostly reflect the posters own comfort level.

Mike-----dual GRT+round backups
 
I have a backup mechanical oil pressure gauge and a backup electric oil temp gauge. I know I am a bit of a dinosaur but I don?t want to put all my faith in electronics with oil pressure. True, as others have said, if the engine monitor fails then you just land. I am thinking of a situation where the monitor is working and showing no/low oil pressure. In this situation you MUST land quickly. A backup will tell you if there is a problem with the monitor/transducer/wiring or if you really do have an oil pressure problem.
My aircraft is in Australia. If all I have is an engine monitor and it fails in the middle of no-where my plane will be stuck there until I can sort out the problem with the manufacturer on the other side of the world. With backup oil temp and pressure gauges I can consider flying the aircraft home and then sorting out the problem with the monitor.
Fin 9A
 
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Finley Atherton said:
A backup will tell you if there is a problem with the monitor/transducer/wiring or if you really do have an oil pressure problem.
Click to expand...
Just an alternate perspective on this situation, Finley... will a backup tell you if there is a real problem or will it only tell you that one of your two instruments has a problem? Further, how will you know which instrument to trust?

I'm probably playing devils advocate and/or am a bit of a hypocrite, since I'm putting an extra ASI and altimeter in to back up my Dynon 180. No backup engine instruments at all on the philosophy that if anything fails in my Dynon, I land and get it sorted out. The backup flight instruments, however, will save me if I lose the screen.

I also probably agree with Randy that the altimeter is not necessary in VFR. (Handheld GPS probably has altitude anyway).
 
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alpinelakespilot2000 said:
Just an alternate perspective on this situation, Finley... will a backup tell you if there is a real problem or will it only tell you that one of your two instruments has a problem? Further, how will you know which instrument to trust?
Click to expand...
I take your point. However if I have at least one instrument showing good oil pressure I will be inclined to believe that instrument and will land at the nearest airport rather than a landing in the nearest clearing. If I had to choose between the two gauges showing different readings I would be more likely to trust the mechanical gauge first (personal prejudice).

Fin 9A
 
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backup attitude indicator

KPmarc said:
I went to Sporty's site to refresh my memory on the cost and found that it's only for sale directly from Castleberry now. Uh-oh, I thought, now that the initial contract is up, they'll jack the price to the moon.

I was pleasantly surprised to see it offered at the same $1995, and you can buy direct from the site.

If I didn't have credit coming from my avionics shop on the ADI, I would have gone this route as a backup attitude indicator.

--Marc
Click to expand...
Is it just me? For that money, I'd get a(nother) Dynon. In my case, to back up my GRT dual EFIS system. You get so much more in one little 3&1/8" hole and internal battery back up available.
 
hevansrv7a said:
Is it just me? For that money, I'd get a(nother) Dynon. In my case, to back up my GRT dual EFIS system. You get so much more in one little 3&1/8" hole and internal battery back up available.
Click to expand...
I guess I'm a 'me too' here. I cannot believe what some want for their electric gyros (bound to wear out or tumble). Give me a couple of good solid state gyros.
 
...... and on separate busses and batteries (I plan a dual electric system).

I've even considered dual pitot/static systems with one feeding each efis??

I want as little mechanical instrumentation and complete redundancy and feel that dual efis/engine monitors from the likes of dynon is by far the most economical??????? I absolutely refuse to have a vacuum system.

I plan to fly IFR regularly and as "hard" as my currency and comfort in the -8 dictates.
 
alpinelakespilot2000 said:
I also probably agree with Randy that the altimeter is not necessary in VFR. (Handheld GPS probably has altitude anyway).
Click to expand...
What use would GPS altitude be if you lost the barometric altimeter when VFR? There can be several hundred feet difference between GPS altitude and barometric altitude. If you want to stay at a VFR altitude, then you need a barometric altimeter. You don't need an altimeter to avoid hitting the ground if you are VFR - the Mk 1 eye ball will be good enough.
 
[QUOTE
I also probably agree with Randy that the altimeter is not necessary in VFR. (Handheld GPS probably has altitude anyway).[/QUOTE]


Also, if your using a GTX 327 transponder it gives presure altitude on the display, it makes a nice back up for your altimeter.
Kevin
 
Kevin Horton said:
What use would GPS altitude be if you lost the barometric altimeter when VFR? There can be several hundred feet difference between GPS altitude and barometric altitude.
Click to expand...

FWIW, over the last couple of years, I've been comparing GPS with WAAS altitude, to posted signs at mountain summit's, national parks, and city limits. Usually, the GPS is easily within 20' of what's posted. I can't say for sure, that the sign is exact altitude; yet the GPS sure is a lot closer than what they use to be!

All this test report, is from the mountain west area.

L.Adamson
 
I noticed that Cessna, Mooney & Cirrus all have 3 backups to their otherwise glass panels: Altimeter, ASI & artificial horizon. Considering that the altimeter & ASI both operate independently of the electrical system, I presume the AH is vacuum operated. These are IFR aircraft and the logic makes sense to me. For VFR, delete the AH.

Too many backups, you add weight, losing one of the benefits of a glass panel.

Before adding backups, review Bob Nuckolls' book and think about his design philosophy, which is to design the electrical system so that no matter what fails, you can make it to your planned destination without breaking a sweat. Rejiggering the electrical system may give more benefit than adding backups.
 
I will likely add also some backup meters but defenitely not for the engine. How likely your EFIS/EMS will fail and after that what are the odds getting also some failure at engine side? The propability exists no doubt but...

So, I would backup with VSI, vertical card compass, altimeter and bank. And it wouldn't harm to have map and/or handheld GPS with you either. Just the system that is not related your electricial system.

One consideration which I've been thinking is airspeed -- if your pitot gets blocked by a bug or such, then you will lose airspeed of EFIS and VSI. However doubling pitot system will be also a bit against odds.
As GPS will give you ground speed you should be able to fly safe even after losing pitot -- just note the wind.

Keep it simple.
 
L.Adamson said:
FWIW, over the last couple of years, I've been comparing GPS with WAAS altitude, to posted signs at mountain summit's, national parks, and city limits. Usually, the GPS is easily within 20' of what's posted. I can't say for sure, that the sign is exact altitude; yet the GPS sure is a lot closer than what they use to be!
Click to expand...
I have no doubt that a GPS with WAAS will display altitudes that are very close to actual geometric altitudes. But please understand that this is very different from the barometric altitude that you read on an altimeter, and that ATC expects you to use.

A barometric altimeter measures air pressure, and converts that to barometric altitude. It would be quite accurate, if the atmospheric pressure vs geometric height relationship always matched that described in the International Standard Atmosphere. But, in the real world, non-standard temperatures have a major effect. The altimeter setting allows you to make the barometric altitude and geometric altitude match at one point. If the temperature is warmer than standard, this pushes the pressure altitudes further apart, so as you climb the barometric altimeter indication increase less than the actual change in geometric altitude. The reverse happens in colder than standard temperatures. The difference between barometric altitude and GPS altitude will often be several hundred feet at typical cross country cruising altitudes.
 
Controversy YOU DON'T NEED ANYTHING

My biggest concern is getting HOME legally, VFR, if my "Glass" fails.

EIS 4000 fails (fuel level, oil temp/press, fuel press, RPM, MAP and so on)? Well I can hear the engine and knowing what I had fuel wise and having time x rate calculations can determine my endurance. Backing up the 20 items this one unit monitors would be difficult, except may be have a spare "brain Box" in the baggage compartment.

Dynon fails (airspeed, altitude and compass)? Well I can see how high I am and know power + attitude = airspeed. Of course the GPS has airspeed and altitude. The most basic back up would be airspeed/altimeter and a wet compass.

Garmin handheld GPS fails (Nav with secondary airspeed and approx alt.)? How about pilotage and dead reckoning? A second cheap GPS would be a backup carried in the "away kit".​

(We can assume we will not lose ALL three or even two at one time.)



After research the fact is I CAN KEEP FLYING with out ANY instruments (any), day VFR in an experimental if I want. FAR Part 91.205 does not apply! (see note 1 below)


Leaglly I can do it but safe and prudent are another issue. Flying along, all is well and the EIS goes dark and I've got no engine of fuel info. Could I fly another hour to get to home field with out all my engine system gauges (EIS4000)? Well that is a call I'd have to make.

I thought about backing up my GLASS with a backup mechanical gauges or dual GLASS. I thought about it and said NOPE, I am VFR and I know if it all went dark I could fly my plane VFR with no panel. The easy things to add and most useful would be mechanical pitot/static altimeter and airspeed instruments. However with a GPS you kind of have a POOR-MANs airspeed/altimeter. Granted its ground speed and the GPS altitude can be off many 100's of feet, but I'm talking VFR, eye balls looking out the canopy.

Bottom Line: Going with bare glass (Dynon, EIS4000, handheld GPS) with no backup. I AM GOING TO TAKE A CHANCE ON LIFE AND BE A WILD MAN AND LIVE ON THE EDGE. :rolleyes: :D


Note (1): I know you say, NO George, you must have all the part 91.205 instruments. NOPE you do not need them in an experimental amateur built plane from a FAR stand point. Don't believe me call the EAA legal dept. I will not argue it. It makes no sense to me but that is actually the LAW! You still may need a transponder or elt but not basic VFR instruments for VFR. However under the catch all, safe operation you may be in violation and I would NOT do it blatantly or cavalierly.
 
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Summary: Thru George's reply....

gmcjetpilot said:
<bunch of snipping>The easy things to add and most useful would be mechanical pitot/static altimeter and airspeed instruments. However with a GPS you kind of have a POOR-MANs airspeed/altimeter. Granted its ground speed and the GPS altitude can be off many 100's of feet, but I'm talking VFR, eye balls looking out the canopy.
Click to expand...
My original list:
FLIGHT:
1. Air Speed
2. Altimeter
3. ?

My current list:
FLIGHT:
1. Air Speed (mechanical, pitot, static
2. Altimeter (mechanical, static)
3. Personal choice, whatever you feel confortable with.
 
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Grayhawk,

I forgot to mention earlier that the simplist backup can be found on a Garmin GPS. A friend used his 196 (?) for all his underhood work on his BFR & did just fine. Check out what the "panel" screen provides. Light weight, uses batteries so it will still work in case of an electrical failure, the 196 can be had second hand for less than $500 or $800 new. Or you could go with some of the more expensive Garmins, but the 196 gets you all the backup you need and you get a GPS you can use in your car, also.
 
Kevin Horton said:
The difference between barometric altitude and GPS altitude will often be several hundred feet at typical cross country cruising altitudes.
Click to expand...

I agree. My thinking has to do with actual distances between the aircraft & rising terrain.

Just remebering the "pre WAAS" old days (around 15 years ago) where you'd be lucky to get elevations within 300' of actual.

L.Adamson
 
RScott said:
Grayhawk,

I forgot to mention earlier that the simplist backup can be found on a Garmin GPS. A friend used his 196 (?) for all his underhood work on his BFR & did just fine. Check out what the "panel" screen provides. Light weight, uses batteries so it will still work in case of an electrical failure, the 196 can be had second hand for less than $500 or $800 new. Or you could go with some of the more expensive Garmins, but the 196 gets you all the backup you need and you get a GPS you can use in your car, also.
Click to expand...
I have a Garmin 196 that I use now.

In the panel upgrade, I am hoping to move to color, and something a little larger (in panel mount). Yes the Garmin 296,396,496,596 are nice but too much $$$$ for such a small size. I like the moving map shown on the AFS EFIS unit but $750 for just software?? Have to think about that; but yes, the moving map as background to flight and engine instruments is neat.

I have also been toying with the idea of just getting a high brightness Optrex display and an ARM 9 based SBC with development system,AHRS, SIRF GPS module, and doing some of my own work. After all, we are 'experimental'. My world would be without Garmin & Jeppensen; but with in flight weather.
 
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I have a 196 and am curious as to where people are mounting the antenna. Can I place the antenna under the cowling as I've seen other people do with panel mount GPS's or will there be too much interference because of the fiberglass? Will the exterior mount antennas from panel mount units work with the 196? By the way, love the extended runway centerlines on the 196.
 
Ultimate backup

Have a look at our Flight II (under Maxi-Singles) at www.MGLAvionics.co.za. Almost a full EFIS with some engine stuff (even fuel flow/level), fits in a standard 3.5" hole and best of all - it is dirt cheap. Altimeter and ASI will most likely outperform whatever you are using now so one could argue as to exactly what is backing up what...
Runs for many hours on a little 9V transistor radio battery if need be.

As to vertical accuracy of GPS receivers, we don't (unfortunately) have WAAS coverage in South Africa but we find modern GPS receivers like the incredible, Swiss made U-Blox we use in our Enigma allows us to fly GPS aided approaches (GPS simulated ILS/Glideslope - we call it GLS) and it puts us onto the touch down spot within a few feet every time - including vertical.

Rainier
CEO MGL Avionics
 
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