What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Backup AI for all glass experimental

timotb

Member
Hi

I built an RV7 panel using an AFS-3500 EFIS with engine sensors, GNS 430, Trutrak autopilot from AFS all powered through Vertical Power VPX pro. Everything works beautifully as expected.

I'm concerned about having some kind basic back up flight instruments. I started with a basic/cheap airspeed and altimeter from ebay. I lucked out on the altimeter but found the airspeed indicator had leaks when I went for the IFR pitot/static test. For $170 an inexpensive new Falcon non-tso'd airspeed indicator from Spruce can be had.

The one that has been giving me frustration is finding an inexpensive but reliable electric attitude indicator for less than $500. Truktrak has them for 1300, occasionally something used might be found for 700-1000 on ebay. Anything new is 2000.

I'm just looking for something basic and simple to get me out of the clouds should there be a failure of the EFIS or electrical system. I have been experimenting with a Samsung Android S2 phone with a attitude app. Sensors seem to be slow to react. Considered experimenting with an IPhone.

Anyone find an inexpensive solution to the electric backup attitude indicator?
 
I doubt you'll find a reliable electric AI for $500. And then, you're still dependent on your electrical system.
A back up EFIS like the GRT Mini or Dynon D6 can be had new for around $1.5 K complete with its own battery. Sell the ASI and altimeter.
 
You can get a Dynon D2 for under $1,000 which is a real attitude display, and has a multi-hour backup battery.

For a total backup, it's usually cheaper to buy a D6, and get a full airspeed, altitude, attitude, heading system for about $1,500, brand new, also with a backup battery.
 
Dynon d6

Im considering the d1 or d2. But first, I want to exhaust the inexpensive route since this is all just for back up.
 
Last edited:
Backup AI

I have a good condition lighted 12v electric attitude indicator 3.25" size with canon connector. Old tech but it works. $600. Email me if you want to see and hear it run in a short video.

Don B

[email protected]

RV 9 Rebuild in Progress
 
Think of it as an Insurance Policy

You're not going to look at it much until you REALLY need it. At that point, I'd want something I know is going to perform, giving me not only reliability, but also dependable information. Maybe everything else on your panel has gone blank while flying instruments at night -This is when you find out that price and cost are not the same thing.
Good luck in your search.
Terry, CFI
RV9A N323TP
 
As well as the instrument you show consider how power is provided. If all the power depends on the VPX it doesn't matter how many AIs are fitted, the VPX is a single point failure. Any reasonable AI will be around $1200 +. My current favourite is the GRT Mini, Mini-X is probably worth while as it does not rely on GPS. Do consider that just because something has a display that looks like an AI does not mean it will perform as an AI does. When installing any un-certified equipment it is the owner who must check the instrument functions as required (expected), in all phases of flight. Cheap and good value don't often go together...

Pete
 
Last edited:
If you have battery backup in the 3500 you already have redundancy, sort of.

I have close to the same equipment sans the VPX. If you loose ships power, you have some time left on the 3500 with the backup battery. If you loose the 3500, the autopilot will keep you straight and level, and you can dial in a turn to get yourself back out of the cloud. Or at least that's been my thinking.

All the same though, I guess if you're intentionally IFR, having another horizon to look at would probably be more comforting.

You're plan still has a flaw in it by planning an electric artificial horizon though. If you loose ships power, you've lost both of your horizons.
 
All good comments, I've considered. My AFS EFIS 3500 has a battery backup. If I go with the D1, which Im strongly favoring, it also has an internal battery for back up.
 
Why not just go for a needle/ ball, airspeed and compass that's all you need to get down through the clouds if everything goes south.
 
Or , you could just refer to your foreflight , or similar ,Attitude / G speed as a basic reference if needed. Plenty of redundancy these days .
 
Last edited:
You can get a Dynon D2 for under $1,000 which is a real attitude display, and has a multi-hour backup battery.

For a total backup, it's usually cheaper to buy a D6, and get a full airspeed, altitude, attitude, heading system for about $1,500, brand new, also with a backup battery.

That was my solution. Both EFISes (EFISi?) have backup batteries, and one (I forget now which :) ) is on the essential bus, as well.
 
Backup?

How about an ADAHRS and a tablet? iLevil has a nice unit

http://www.aviation.levil.com/ilevil-aw.html

Garmin too. GDL family of options.

Garmin

Others as well.

Then an android tablet with software will get you a lot more than just backup your other instruments.

Mount the tablet on the firewall or make it mountable in line of sight.

Tablets have battery backup.

AND Hardware and Software is improving according to Morre's Law

CC
 
As well as the instrument you show consider how power is provided. If all the power depends on the VPX it doesn't matter how many AIs are fitted, the VPX is a single point failure. Pete

I apologize for the thread drift to the OP.

Not entirely accurate. It depends on which model VPX that you have. The current Pro model has two buses within the unit. If one bus fails, the other remains active. While this doesn't resolve all risks, it does mitigate some.

There are also ways to mitigate power related risks outside of the VPX as well as other single points of failure in a typical electrical system. For example, my RV-10 has two independent electrical buses that can be run independently or in parallel. I have two alternators, although the backup one has significantly less capacity. All my EFIS have internal backup batteries.

The VPX can switch two circuits to the EBUS. I also have other switches (external to the VPX) that allows me to switch critical components needed in IMC to the EBUS as well.

While have reliable avionics is import, even more important is having a good electrical system design and complete understanding of all the failure modes and procedures to mitigate those failures.

Back to the thread......

Both the Dynon, Trutrak, and GRT products mentioned are all nice backup instruments. I have a Trutrak Gemini. If I were to purchase again, I would probably consider a Dynon or GRT mini solution. I'm also an IT guy, which makes me a little skeptical with software bugs in avionics. If planning on flying in IMC, I would recommend that your backup be from a different vendor. Granted this risk of a software bug taking out everything is very small, but it is a risk. With choosing a different vendor, it ensures you that there shouldn't be any common code.
 
I bought a used Dynon D10A thinking that if/when I upgraded further from steam to glass I could always sell it again to help finance the change. But now that i've flown with it, and looked at what else is available for backup instruments, I don't think I will. It's a really, really good backup unit all on its own.

Still, watch the classifieds here for D6's and D10's coming up for sale used as people upgrade. They're great buys.
 
Also, any backup instrument that has a backup battery eliminates the single point of failure from a power side. I'm not sure if the Gemini has it, but it is available for Dynon D1, w, 6 & 10; GRT Mini and the TruTrak ADI, all of which are great backup instruments.

From a software side, the ADI is not the same software as any of the TruTrak EFIS products were, or the Gemini. The Dynon D6/10 is different software from the Skyview system. The D1/2 is yet different software. I think thenGRT mini is likely the only one mentioned that could possibly share software bugs with heir bigger EFIS products.
 
Also, any backup instrument that has a backup battery eliminates the single point of failure from a power side. I'm not sure if the Gemini has it, but it is available for Dynon D1, w, 6 & 10; GRT Mini and the TruTrak ADI, all of which are great backup instruments.

From a software side, the ADI is not the same software as any of the TruTrak EFIS products were, or the Gemini. The Dynon D6/10 is different software from the Skyview system. The D1/2 is yet different software. I think thenGRT mini is likely the only one mentioned that could possibly share software bugs with heir bigger EFIS products.
 
You can get a Dynon D2 for under $1,000 which is a real attitude display, and has a multi-hour backup battery.

For a total backup, it's usually cheaper to buy a D6, and get a full airspeed, altitude, attitude, heading system for about $1,500, brand new, also with a backup battery.

Im considering the d1 or d2. But first, I want to exhaust the inexpensive route since this is all just for back up.

The Dynon Pocket Panel is the cheap route. No wiring, no connection to to the pitot / static system, etc.

Between that and the 496 I have kept in the panel, I can aviate and navigate should for hours should I have an electrical failure or pitot / static obstruction (think ice).
 
All good responses from previous posters, not much left for me to add other than the product mentioned are all favorites of ours and our customers. The GRT mini has become quite popular, but in an existing panel can be a bit more of a difficult retrofit with the square hole, but will be much easier when the release their 3" mounting hole kit. The Dynon D1/D2 are quite popular, but if you're going to permanently mount one of them, then the D6 is a much nicer looking solution as you can make it aesthetically more appealing (as you can with the TruTrak as well).

All of them are in the $1K - $1500 price range (and all things considered offer a fantastic value for the price). I built an RV6 years ago (VFR) where the ONLY flight instrument I had was one of the original D10's and it flew that way for many years and it was plenty sufficient...just to give you an idea.

Either way you'll end up with a good backup. Just my 2 cents as usual!

Cheers,
Stein
 
Also, any backup instrument that has a backup battery eliminates the single point of failure from a power side. I'm not sure if the Gemini has it, but it is available for Dynon D1, w, 6 & 10; GRT Mini and the TruTrak ADI, all of which are great backup instruments.

From a software side, the ADI is not the same software as any of the TruTrak EFIS products were, or the Gemini. The Dynon D6/10 is different software from the Skyview system. The D1/2 is yet different software. I think thenGRT mini is likely the only one mentioned that could possibly share software bugs with heir bigger EFIS products.

I'll repeat what I've said here many times before...n-version programming does NOT solve the problem. It has been demonstrated that even having completely different teams of developers, albeit working to the same requirements, will generate *the same types of software errors*. There are many reasons for this, but the bottom line is that relying on "different" software is a facile approach to the reliability problem.
 
I'll repeat what I've said here many times before...n-version programming does NOT solve the problem. It has been demonstrated that even having completely different teams of developers, albeit working to the same requirements, will generate *the same types of software errors*. There are many reasons for this, but the bottom line is that relying on "different" software is a facile approach to the reliability problem.

Yes - but most manufacturer's work to slightly different requirements (everyone considers their's to be the best), so the result is that you can avoid simple common-mode code bugs.

The big old "Heavy Glider" had a back-up software flight control system that did the same thing as the primary but was thinned down considerably - so the requirements documents looked completely different. And....the BFS had its own completely different bugs than the PASS. :rolleyes:
 
Also, any backup instrument that has a backup battery eliminates the single point of failure from a power side. I'm not sure if the Gemini has it, but it is available for Dynon D1, w, 6 & 10; GRT Mini and the TruTrak ADI, all of which are great backup instruments.

From a software side, the ADI is not the same software as any of the TruTrak EFIS products were, or the Gemini. The Dynon D6/10 is different software from the Skyview system. The D1/2 is yet different software. I think thenGRT mini is likely the only one mentioned that could possibly share software bugs with heir bigger EFIS products.

I have a battery available for all the Gemini product lines as well.
 
Zombie Thread

I'm looking for an electric AI and will not consider the D1.

I''ll have the Dynon D-100 as my primary, and below it I want round dial Airspeed, Electric AI, and Altimeter. The AI will be wired to my Emergency switch so if I have Alternator problems everything is powered off except the AI and the left ignition which are then powered direct from the battery (approx 30 mins to get on the ground)

I'd go with a vacuum AI if I had a vacuum system, but that is also not the answer.

So.. what you think?

Skysports, Falcon, RC Allen....

I'm expecting ~1500$ for the instrument. I don't want to be penny-wise as they say.
 
I had an RC Allen electric AI for a couple of years. It was a real piece of junk - but it was "TSO". I sold it for about the same money to buy a Dynon D10A. The D10A was flawless for five years and now is the "backup" for a single 10" SkyView back fit in my RV-8A I sold.

The D10A fills the same hole as an electric AI - provides full EFIS capability and is, in my experience, far more reliable.

Carl
 
I think the Trutrac ADI (not ADI Pilot) is very hard to beat as a bone simple backup AI. Besides, it may be the only one available in a 2-1/4" format. It has saved my bacon.
 
Thanks for the thread!

Thanks to the OP for the thread.

I just looked up the Trutrak ADI, that would make a nice backup for me, I have an empty spot for one now in just the right spot on my panel. Anyone have a used one available?

Jim
 
Pulled the trigger

I've purchased the Gemini ADI.

Now I'm going back and forth about wiring.

Option 1) Wire it to my GX-60 for GPS track input
Option 2) Don't wire the GPS and be in the habit of slewing it to known headings.

Option 1 makes sense, since it is the designed operational mode
Option 2 makes sense since it fits the usual ground mode, set the the DG that we learned for our PPL.

I've seen some posts about people in OPT2 mode, but they were 3+ years ago.

Any current thoughts are appreciated.
 
I have the Gemini PFD as my backup. It's wired to my GTN 650. Not sure that really helps with your decision as I never even considered not wiring it to a GPS when I built my wiring harness and later installed it in the panel
 
Last edited:
I've purchased the Gemini ADI.

Now I'm going back and forth about wiring.

Option 1) Wire it to my GX-60 for GPS track input
Option 2) Don't wire the GPS and be in the habit of slewing it to known headings.

Any current thoughts are appreciated.

Have the best of both worlds, and put the GPS serial line on a switch. Turn GPS aiding off if you want.

My guess is, after only a couple flights, that switch would stay on all the time.
 
I've purchased the Gemini ADI.... (snip)

Option 2) Don't wire the GPS and be in the habit of slewing it to known headings.

From a pros/cons list what advantages, if any, does this provide over the serial input from the GX-60? I'm not aware of any. I assume this is more of a "is it worth the work of breaking into the existing harness"?

I say wire it up to the GX-60
 
I was thinking that my primary DG is from the magnetometer on the D-100, so wouldn't I want my backup to also be based on magnetic?

Then if I'm navigating on either of them the data is the same.
 
If it were me, I wouldn't want to ever look at an unslaved DG if I didn't have to. :) If the ADI is your standby/backup only, do you really care if your primary is magnetic based and your backup track based? In a failure situation, you'll have one or the other. If the GPS fails, you'll have an unslaved DG on the Gemini anyway.

Cliff's notes: I'd hook up the GPS to it :D
 
Just my 2 cents. Since 2006 or so I've had the 3 inch version of the TruTrak ADI with GPS ground track and it's been a wonderful, reliable instrument for flying with reference only to instruments. I put it on a switchable secondary electrical system just in case primary system ever faiis however TruTrak sells a more elegant solution for that. The 3 inch version is now only available occasionally on eBay, usually about $600 when I've seen them. I bought my 3 incher from Gulf Coast and think I paid $1100. The 2 inch version which TT still sells is pretty pricey at $1300. Electronics generally go down in price over time, not up. Don't know what the story is with the 2 inch ADI that makes it an exception to this trend.

The Dynon D1/D2, BTW, is totally dependent on a GPS signal. Yes, it has MEMS and AHRS chips but for some perverse reason still requires a GPS signal in order to function. Lose your GPS signal for any reason and you've lost your attitude. The TruTrak ADI is a self-contained attitude instrument, using GPS only for ground track.

Although TT still has the ADI in the 2 inch format, I think it was a poor decision for them to do away with the larger version. I suppose it was to force customers to go to the Gemini if they want an attitude indicator larger than 2 inches. Having not looked into it I don't know this but I suspect the Gemini works the same as the ADI, but clutters up the screen with altitude and airspeed info - things we've always got with even the simplest GPS and altimeter. I love my 3 inch ADI with its straightforward display of just attitude and heading . . . and its instantaneous responsiveness. It suits my fingertip control aircraft perfectly when hand flying in the soup. I hope it continues to run forever.
 
Just my 2 cents. Since 2006 or so I've had the 3 inch version of the TruTrak ADI with GPS ground track and it's been a wonderful, reliable instrument for flying with reference only to instruments. I put it on a switchable secondary electrical system just in case primary system ever faiis however TruTrak sells a more elegant solution for that. The 3 inch version is now only available occasionally on eBay, usually about $600 when I've seen them. I bought my 3 incher from Gulf Coast and think I paid $1100. The 2 inch version which TT still sells is pretty pricey at $1300. Electronics generally go down in price over time, not up. Don't know what the story is with the 2 inch ADI that makes it an exception to this trend.

The Dynon D1/D2, BTW, is totally dependent on a GPS signal. Yes, it has MEMS and AHRS chips but for some perverse reason still requires a GPS signal in order to function. Lose your GPS signal for any reason and you've lost your attitude. The TruTrak ADI is a self-contained attitude instrument, using GPS only for ground track.

Although TT still has the ADI in the 2 inch format, I think it was a poor decision for them to do away with the larger version. I suppose it was to force customers to go to the Gemini if they want an attitude indicator larger than 2 inches. Having not looked into it I don't know this but I suspect the Gemini works the same as the ADI, but clutters up the screen with altitude and airspeed info - things we've always got with even the simplest GPS and altimeter. I love my 3 inch ADI with its straightforward display of just attitude and heading . . . and its instantaneous responsiveness. It suits my fingertip control aircraft perfectly when hand flying in the soup. I hope it continues to run forever.

Hi Mike, I'm happy to see if I can clear a little up for you.

We do offer two versions of the Gemini, the ADI and the PFD. The ADI is exactly what you're expecting; a glass version of our older mechanical ADI. No airspeed tape, no altitude tape, GPS used only for the ground track. The best part is, it's actually cheaper (as a new unit) than the ADI was when we still manufactured.

On the 2" ADI, think about a comparison with cell phones. Each year, the internal components get smaller and each version costs more than the last. It's the same thing here. It actually costs more to make it smaller.

The reason behind discontinuing the ADI 3 was due to the release of the Gemini. Glass is all the rage and it allows us to make the product lighter, thinner, and with zero moving parts.

I hope this helps a little!
 
Thank you Lucas. Didn't now about the bare bones Gemini but then I haven't been paying attention. What I AM paying attention to is my position on the waiting list for that ECO. Please stop spending time on the forum responding to dodos like me and go light a fire under those vendors' rear ends that are holding up this project :)
 
Back
Top