Thoughts on backup AI

Bill

Bill

Touchdown! Greaser!
PoA Supporter
Joined
Mar 2, 2005
Messages
15,344
Location
Southeast Tennessee
Display Name
Display name:
This page intentionally left blank
So I was pondering the use of an electric backup AI like the one sportys has that can replace the TC. This seems like a great idea if both your AI and DG are vac powered, but I wonder if it is quite as important with an electric DG/HSI.

I fly IFR using DG as primary roll and ALT as primary pitch, with the other instruments as verification. If a vac DG and AI went out in turb, and the whiskey compass was bouncing all around, then yes I think the elect backup AI would be great.

But, if a vac failure only takes out the AI, and the elect DG is still good, then I wonder how much the backup AI really helps.

Of course, if both the vac and elect fail, then a battery backup AI is about the only thing that will keep you shiny side up.

Discussion?
 
I'm just a lowly PP (no IR) but I have thought about it as it's been bandied about.

To me it is less about the value of the backup AI then it is about the value of having the TC in the panel.. If (like most people) it is used primarily as a "skid indicator" instead of a turn coordinator, then that hole is better used by something else. I guess as I've thought about it, it seemed to me that there were other ways of getting attitude information if you lost your AI, but why not have this in there if you're not using the TC to make timed turns?

Anything that can help to keep you from falling farther behind when the chips are down would seem like a wise investment to me.
 
Damn....Already want to upgrade and we haven't even taken possession of the plane!!:eek: What kind of guy did I decide to partner up with??:D Just don't put me in the poor house.
 
backup AI, IMO would save the day in a conventional vaccum powered panel with a vaccum failure. I had a vaccum failure in VMC so it was no big deal, but I was happy to be able to see the symptoms as the gyros started to wind down. Of course technically you can fly the thing safely on needle, ball, and airspeed, but the accident record doesnt seem to support this.

Ken Ibold posted earlier about how he had a wiring harness installed by his A&P that a solid state electric AI plugged into. This made the AI not permanent, therefore not requiring a 337, or for the AI to be certified. I wonder if you could do the same for a Dynon 10A, i think it fits in a standard hole, but the display needs a lot of room around it. Would be an even better backup than a standard size AI.

As far as you wondering about losing the AI and flying on with the DG and Alt, go try it. I suspect that it will be much easier than flying with an AI and DG failure. Then decide if you still want the electric AI backup.

Personally, if I had the dough, id get the AI instead of the TC. or a backup vaccum system.
 
Funny you should mention this. I was pondering the question today ( when I got the new Sporty's Catalogue) as to whether one would be smarter getting a 430 or the New Electric AI.

The GPS makes things soooo easy but the back up AI can save a life IMHO. Yes we IR guys train to fly partial panel but Why fly it if you don't have to . The price is not too bad and I think It would bring you a LOT of piece of mind.

My dad has a great way of evaluating Health and Saftey issues. He is a family doc and when he has a patient who smokes or drinks too much and the patient says I don't have to quite I'll be fine. My dad asks them " What would you want your son or daughter to do?"

So Bill if it were your wife in the plane or you kids would you want them to rely on the TC and whiskey compass in a vac failure in IMC or would you want them to have the back up AI?( all assuming cost is not the issue)
 
AdamZ said:
The GPS makes things soooo easy but the back up AI can save a life IMHO.
Click to expand...

So that brings up an interesting question. The Garmin x96 family have a pseudo panel page that basically shows you a set of gauges based on the GPS reciever (see pic below). I wonder if the simulated DG and TC are useful enough to provide actual roll information in the event of a worst case vac and elect failure? Anyone with these products know?

So Bill if it were your wife in the plane or you kids would you want them to rely on the TC and whiskey compass in a vac failure in IMC or would you want them to have the back up AI?( all assuming cost is not the issue)
Click to expand...

Food for thought, to be sure.
 

Attachments

  • pt-GPSMAP396Large019.jpg
    pt-GPSMAP396Large019.jpg
    43.3 KB · Views: 16
Bill Jennings said:
I wonder if the simulated DG and TC are useful enough to provide actual roll information in the event of a worst case vac and elect failure? Anyone with these products know?
Click to expand...
Garmin's test pilot demos flying a single engine ILS in a Baron with a towel covering his head and blocking out everything but the x96 instrument screen. Not been onboard myself, but those who saw it using a 396 report it resulted in an acceptable if not particularly smooth approach.
 
Ken Ibold said:
Not been onboard myself, but those who saw it using a 396 report it resulted in an acceptable if not particularly smooth approach.
Click to expand...

Impressive. So, it *could* possibly get you out of trouble in a full failure situation.
 
AdamZ said:
Funny you should mention this. I was pondering the question today ( when I got the new Sporty's Catalogue) as to whether one would be smarter getting a 430 or the New Electric AI.

The GPS makes things soooo easy but the back up AI can save a life IMHO. Yes we IR guys train to fly partial panel but Why fly it if you don't have to . The price is not too bad and I think It would bring you a LOT of piece of mind.
Click to expand...

After reading Ken's response above to my 396 questions, I'd say of the three, the 396 would be what I'd buy first:

1.) The moving map and weather is useful everyday.
2.) In the event of a full electrical out, not only can it guide you to nearest or out of the soup, but you could use the pseudo panel to fly your way out.
 
Bill Jennings said:
After reading Ken's response above to my 396 questions, I'd say of the three, the 396 would be what I'd buy first:

1.) The moving map and weather is useful everyday.
2.) In the event of a full electrical out, not only can it guide you to nearest or out of the soup, but you could use the pseudo panel to fly your way out.
Click to expand...

Boy, I sure think I'd want to give that a try before betting the farm on it. :yes:
 
i guess i forgot about the gps. most of the time when i fly ifr i dont have a handheld. it will probably get you out of a jam, just keep the batteries up, and practice flying on it so you dont have to teach yourself how when the **** hits the fan!
 
Instrument redundancy

I went thru this analysis back in late 1999 not long after the Jakoby accident. I figured that if the Bonanza Society's recognized expert in partial panel flight couldn't handle it with the whiskey compass, what chance did I have?
http://www.ntsb.gov/NTSB/brief.asp?ev_id=20001212X20151&key=1
So I spent the $$$ to put in the electric gyro compass and Sandel HSI, keeping the vacuum AI and DG along with the electric TC. I'm comfortable with this setup, using a Garmin 155 to feed GPS to the Sandel.

The Sandel minimizes scan. In the T210, the location of a moving map elsewhere on the panel would detract from scan ability.

I vote for full redundancy in electric and vacuum driven instruments, without reliance on the whiskey compass.
 
Re: Instrument redundancy

Dick Madding said:
I vote for full redundancy in electric and vacuum driven instruments, without reliance on the whiskey compass.
Click to expand...

If you have the panel space, I see the logic in that approach.
 
Bill Jennings said:
So that brings up an interesting question. The Garmin x96 family have a pseudo panel page that basically shows you a set of gauges based on the GPS reciever (see pic below). I wonder if the simulated DG and TC are useful enough to provide actual roll information in the event of a worst case vac and elect failure? Anyone with these products know?
Food for thought, to be sure.
Click to expand...

I've attemtped to fly with that "panel" on my 296 and while it definitely possible, it's not very comfortable. For one thing, the 296 and 396 update at 1 Hz which is a long time for feedback, especially if your scan happens to be on something else for many updates. There's also no real pitch information, something I feel is crucial. If you can live without that, your TC and compass will be adequate IMO. What I do believe you get with the x96 is a good stable heading source (as long as the GPS keeps working) so it may indeed be a good backup to a DG.

To answer your original question, in my airplane I have two vacuum pumps and warning lights on each source near the gyros. The only thing the pumps power is the AI (which also drives the autopilot) as I have an electric HSI. I have always felt that a loss of the AI in IMC near the ground would be dicey at best (and deadly at worst) and therefore jumped at the chance to install one of the new crop of electric AIs for backup. I had contemplated going the route that Ken did (velcro an unapproved electronic AI into the panel) and I also looked at installing a second identical vacuum AI with a transfer switch so I could still use the autopilot if the primary AI failed (that was a non-starter since the autopilot has to be adjusted for the specific AI it's attached to). I ended up with Sporty's electric AI (actually made by Castlebury). It's currently located at the top of the "six pack" where the original AI was and that was moved to the left of my turn gyro (the STC allows you to replace the turn gyro with the AI but I elected to keep it) but I plan to swap those two soon so that the backup (original) AI is closer to the primary one for easy comparison. Actually I had told the shop that did the install to move the turn gyro over but they failed to do so and gave me some BS about it wouldn't fit (it will I checked it myself).

One issue worth mentioning is that electric AIs erect much more slowly than vacuum powered ones. It's not unusual for me to find that it hasn't completely erected when I'm ready for takeoff several minutes after starting my engines. There is a "quick erect" knob, but IME if it's not already self erected, pulling the knob sets it to the wrong attitude (my airplane sits on the ground about 3 degrees nose up and the know sets it to level) and it takes just as long for it to correct as it would have to complete the original alignment.

I'm also finding that it's difficult add a second AI to my instrument scan, old habits die hard I guess.
 
lancefisher said:
----------------snip----------------
One issue worth mentioning is that electric AIs erect much more slowly than vacuum powered ones. It's not unusual for me to find that it hasn't completely erected when I'm ready for takeoff several minutes after starting my engines. There is a "quick erect" knob, but IME if it's not already self erected, pulling the knob sets it to the wrong attitude (my airplane sits on the ground about 3 degrees nose up and the know sets it to level) and it takes just as long for it to correct as it would have to complete the original alignment.

I'm also finding that it's difficult add a second AI to my instrument scan, old habits die hard I guess.
Click to expand...

Jakoby apparently took off with his electric TC not operating, and subsequently suffered a vacuum failure. While the Wx wasn't that bad- 2-1/2 miles of visibility, light rain and mist, 600 foot scattered, 1,300 foot broken, and he reportedly suffered the failure at 900 ft. Unfortunately he chose to follow ATC instructions regarding assigned altitude [in IMC] and making turns. While the NTSB stresses the medication he was on as a major causual factor, he had been taking this medicine since 1976, and in my opinion his decision to attempt to follow ATC instructions rather than declare an emergency and hold his [trimmed] climb attitude and heading until on top [approx. 3000 ft.] was the major causual factor. I took note of this decision and its consequences should I find myself in a similiar predicament [but I won't be taking off into any IMC/night with TC inop].

My electric turn coordinator is sluggish when cold, which is one of the reasons I use a small space heater with built-in fan on a timer in the cabin at OATs of 45F and below.
 
I've had both power (vacuum) and instrument failures cause me to lose my AI in flight. In both cases I still had the electric HSI, so it wasn't quite as bad as it could have been. However, I am still convinced that a second AI independently powered is a Very Good Thing, and when I owned an airplane I installed one right after the primary instrument failed. The first rebuilt AI after that incident failed in a different way, and the backup made that a non-event, even though it was IMC in mountain waves and I constantly needed to adjust pitch and power to maintain altitude.

I will definitely put one in on the next airplane I buy if it doesn't have one, and if I had panel space I might even want a total of three (pilot, copilot, standby) so that I could use the "two out of three" principle to determine which instrument had failed. I don't like to work hard in IMC, even though I practice partial panel so that I can do it if the need arises.
 
Assuming one's partial panel skills are up to par, the critical issue is recognizing that the AI is failing. During my last IPC we did plenty of partial panel so both I and my instructor knew I could do it. Then, in the sim, he put me in a high-workload environment and failed the AI. I followed that little bastard right into the ground. He told me that a huge percentage of GA instrument pilots do the same thing. A Sporty's backup AI is being installed in my plane right now. It's real value is to help me recognize an AI problem early (I hope).

Regards,
Joe
 
Joe B said:
Assuming one's partial panel skills are up to par, the critical issue is recognizing that the AI is failing. During my last IPC we did plenty of partial panel so both I and my instructor knew I could do it. Then, in the sim, he put me in a high-workload environment and failed the AI. I followed that little bastard right into the ground. He told me that a huge percentage of GA instrument pilots do the same thing. A Sporty's backup AI is being installed in my plane right now. It's real value is to help me recognize an AI problem early (I hope).

Regards,
Joe
Click to expand...


I agree with all of that. I've run several scenarios with OnTop where the vacuum system or AI fails (that program has some fairly realistic failure modes) and even when you know it's going to happen sometime during a "flight" it can easily take you by surprise when the AI slowly rolls over. I did find that after some practice with this, I could recognize the failure in a reasonably short time, even without the sensations of actual motion. A big remaining issue IMO is that it's much easier to recognize that "something ain't right" than to sort out exactly what's wrong. This is the typical sequence that I found with OnTop:

1> I noticed that I was drifting off whatever I was tracking.

2> I noticed that the DG was turning when I held the wings "level" according to the failing AI. Notice that at this point it looks just like rapid DG precession and you could actually have both problems if the DG and AI are both vacuum powered. Checking the suction gauge at this point would help, but IME that's not a typical response because you are fighting for control. This is where a glance at a second AI would immediately convince you that one of the AIs has failed and since you were using the primary AI when things got out of whack, it follows that the backup AI is very likely telling the truth.

3> Comparing the DG rotation direction with the T/C shows that they agree assuming the DG is still working, if not you must bring the suction gauge into the equation to determine what's not working. This is nowhere near intuitive and I believe it's easy to make the wrong call at this point, especially if you've experienced rapid DG precession before as the human mind tends to interpret things per our preconceived notions. And keep in mind that on an approach or departure in IMC, your heart will be racing and your mind will want to freeze up at this point. OTOH if you had a second AI and rolling that one level stops the turn, you have an easily recognizable situation and things are basically back under control at that point.

4> Once you convince yourself in step 3 that the AI is lying, you can simply stop the turn with the turn gyro, cover the failed AI and proceed on partial panel.

Something that would really be nice is an electronic way to compare the two AIs and warn the pilot when they differ significantly. I do have two waning lights below the HSI (they wouldn't fit by the AI) so I would know without looking at the suction gauge (way over on the right side of the panel) if I had lost power to the AI, but that doesn't tell anything about a failure of the AI itself.
 
Lance, I too use On Top, and was extremely surprised at how hard it is to catch a failing AI even though I'd programmed it to fail just minutes before! So I am concerned; however...
My AI is the only thing in the airplane that uses vacuum. I have two full size vacuum pumps, the regular one on the engine and an electric motor powered backup (gotta flick a switch to activate it). The electric STEC50 A/P runs from its electric TC, the HSI is electric, the GPS is electric. Since I don't have any more panel space for a b/u electric AI, and since I feel much more vulnerable electrically than vacuum-wise; I don't think a b/u electric AI would be of much help.
Am I missing something in my thinking here?
 
Lance F said:
Lance, I too use On Top, and was extremely surprised at how hard it is to catch a failing AI even though I'd programmed it to fail just minutes before! So I am concerned; however...
My AI is the only thing in the airplane that uses vacuum. I have two full size vacuum pumps, the regular one on the engine and an electric motor powered backup (gotta flick a switch to activate it). The electric STEC50 A/P runs from its electric TC, the HSI is electric, the GPS is electric. Since I don't have any more panel space for a b/u electric AI, and since I feel much more vulnerable electrically than vacuum-wise; I don't think a b/u electric AI would be of much help.
Am I missing something in my thinking here?
Click to expand...

The thing you're missing is a failure of the AI itself, not the power source for it. My MSE had the same set-up, with a vacuum pump and a standby electric pump in the tail. When my AI started indicating a climb with no corresponding change in VS or altitude, I checked the suction - looked good, activated the standby pump just in case, still looked good, and STILL the AI indicated an increasing rate of climb, till it showed 20+ degrees nose up, and then it started to indicate a roll to the left.

I consider myself fortunate that it started to diverge in pitch first. If it started to flake out in roll at first, I think I'd have been more likely to follow it and possibly lose control. I got out a cover and flew the rest of the trip partial panel, and I was missing the AI on the ILS approach that ended the trip. The return trip was in VMC, and a replacement AI was installed, along with a backup. The replacement AI failed in a similar fashion later, but the backup AI made it a non-event. The third AI was the charm, and was operating well when I sold my interest in the airplane a year later.
 
Last edited:
Lance F said:
Since I don't have any more panel space for a b/u electric AI,
Click to expand...

FWIW, I think you could mount the T/C somewhere off the panel and install a backup AI where it was.

and since I feel much more vulnerable electrically than vacuum-wise; I don't think a b/u electric AI would be of much help.
Am I missing something in my thinking here?
Click to expand...

As I stated earlier, I think that we are most vulnerable when near the ground on approach or taking off. And unless you always use the autopilot when in IMC close to the ground, the fact that your A/P is rate based won't help. Even though you are mostly electric, an electric AI would still provide a quick way to determine if your primary AI has failed internally or for lack of suction. If you really want independence from the aircraft electrical, there's always the "lifesaver gyro" from Mid Continent which comes with an internal battery for backup power.

http://www.lifesavergyro.com
 
Lance F said:
Am I missing something in my thinking here?
Click to expand...

A back-up source of electricity? My cockpit is like yours - all electric except for the AI. After it sank in just how thoroughly screwed I'd be if the electrons stopped flowing in IMC I installed a standby alternator. I've a 296 on the yoke - but it's not my only line of defense!

Regards,
Joe
 
Joe B said:
Assuming one's partial panel skills are up to par, the critical issue is recognizing that the AI is failing. During my last IPC we did plenty of partial panel so both I and my instructor knew I could do it. Then, in the sim, he put me in a high-workload environment and failed the AI. I followed that little bastard right into the ground. He told me that a huge percentage of GA instrument pilots do the same thing. A Sporty's backup AI is being installed in my plane right now. It's real value is to help me recognize an AI problem early (I hope).

Regards,
Joe
Click to expand...

I had a vacuum failure in VMC and watched the AI spin down ever so slowly. When it goes TU I am going to replace it with one that has a flag on it to tell me it is not working.
 
Bill:

I've wrestled with this too. I've been in sim training where they failed both the DG and AI and I caught it, but I was about 2,000 feet AGL being vectored for an approach. While I did recover, if it had happened lower, I wouldn't have.

The KFC-200 is connected to both the AI and HSI; so, if you lose one of those, your AP is off line (it's happened to me when I lost an HSI). You shouldn't have the gradual failure of the AI problem with the electric HSI. (IN my plane, I have the Sandel). In the sym, where both failed, that is much less likely in my plane with the vacuum (actually pressure) AI but the electric HSI (Sandel).

I've become comfortable without the backup AI because two separate systems would have to fail. Of course, engine failure could cause the vacuum to go quickly and the electric to have limited time (especially in a single).

I also have a 396 and have flown approaches using it; it does refresh slowly and in turbulence could be a real challenge. The turn and bank would also be a real challenge in turbulence.

The 436 seems to do a much better job at refreshing and guys that have purchased them, have told me it's a much better back up.

It's all trade offs. Of course, you'll have to decide. I really like the backup AI if it has battery power. But, as has been said, if you have other back up systems and different sources for the AI and HSI, you're certainly in better shape than a lot of GA guys.

Best,

Dave
 
smigaldi said:
I had a vacuum failure in VMC and watched the AI spin down ever so slowly. When it goes TU I am going to replace it with one that has a flag on it to tell me it is not working.
Click to expand...

All of our club planes have a low vac light. Nice and red and bright, hard to ignore.
 
Bill Jennings said:
All of our club planes have a low vac light. Nice and red and bright, hard to ignore.
Click to expand...

I have two lights but I would still like the reminder flag. That was because when the failure happened you would scan the instrument see it was tilting and start to make correction without thinking. When you saw the light and would take out the correction
 
smigaldi said:
I have two lights but I would still like the reminder flag. That was because when the failure happened you would scan the instrument see it was tilting and start to make correction without thinking. When you saw the light and would take out the correction
Click to expand...

OK, got it. I'll have to check, but I don't think our to be AI has a flag. :(
 
Btw are you looking at Stand-by vacuum systems at all? I have that in my plane. There are limitation to it's effectiveness but cost wise it is a inexpensive way to have another level of redundancy to your system
 
smigaldi said:
Btw are you looking at Stand-by vacuum systems at all? I have that in my plane. There are limitation to it's effectiveness but cost wise it is a inexpensive way to have another level of redundancy to your system
Click to expand...

Not yet, but that is something that could be put in at our first annual if we aren't sqwauked to death.
 
Joe B said:
A back-up source of electricity? My cockpit is like yours - all electric except for the AI. After it sank in just how thoroughly screwed I'd be if the electrons stopped flowing in IMC I installed a standby alternator. I've a 296 on the yoke - but it's not my only line of defense!

Regards,
Joe
Click to expand...
I wonder if anyone has an STC for a standby alternator for an IO360 in a Mooney. I can't imagine where you would put it, but it would be nice.

Does anybody know if an STEC T&B can be remotely mounted to free up the space for the backup AI?
 
Lance F said:
Does anybody know if an STEC T&B can be remotely mounted to free up the space for the backup AI?
Click to expand...

I don't KNOW, but given how Cessna installed the one for the KAP 140 in the G1000-equipped birds (stuffed behind the MFD, invisible until you take apart the panel), I'd think you could hide it somewhere.
 
Bill Jennings said:
Looks like the Sportys DOES NOT have an internal battery.
Click to expand...

That's correct. It does have an inclinometer and internal lighting, but no battery. It doesn't seem all that difficult to rig an external one though. But since the chances of losing both your suction and electric power, I don't see much point if your primary AI is air powered.
 
Lance F said:
I wonder if anyone has an STC for a standby alternator for an IO360 in a Mooney. I can't imagine where you would put it, but it would be nice.

Does anybody know if an STEC T&B can be remotely mounted to free up the space for the backup AI?
Click to expand...

An inexpensive and pretty good alternative to a standby generator is adding a low voltage alarm and replacing your battery before it loses much capacity.
 
lancefisher said:
An inexpensive and pretty good alternative to a standby generator is adding a low voltage alarm and replacing your battery before it loses much capacity.
Click to expand...
If you've got an engine monitor (and in a Mooney, you should), it should have a voltage alarm function.
 
lancefisher said:
An inexpensive and pretty good alternative to a standby generator is adding a low voltage alarm and replacing your battery before it loses much capacity.
Click to expand...
Good points, Lance. Thanks. My JPI will start flashing in a low voltage situation, and I bought a new Concord sealed battery just last year. It is my hope and expectation that that will be enough to get me on the ground or into VMC.
 
You must log in or register to reply here.
Back
Top