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Good AI backup, wish me luck
After having both a vac pump failure and an AI failure (not on the
same flight ) I decided its really time for a backup. I always consider my Mooney to be an "IFR anytime" type of plane, in that I consider it a solid IFR platform. When the vac pump goes out alarms starting sounding, my voice annunicator starting saying "check vac pressure" and the needle goes to 0. It's pretty obvious. I do a voluntary IPC every 6 months with a local DE and always do partial panel approaches so I'm as comfortable as you can be with that. A couple weeks ago I had my AI go out. WOW, that's another story!! The thing slowly rolled 30 degrees off and REMAINED RESPONSIVE!! When I banked, it banked, when I pitched, it piched. Figuring out that it was dead could be hard and it would be easy to miss it. I decided I need a back up and those vac backup systems are a waste of money(Precise Flight, electric vac, etc). After getting it back from overhaul my partner reported that it did it again! I called a couple gyro places and they said the vac AIs don't last very long because they have a stream of "dirty" air running through them. The electrics last much longer. So I'm getting an electric AI installed as my backup. I noticed that the non-TSO'd electric AIs are almost $1000 less than the TSO'd ones. I asked my mechanics and the FSDO and they said I could probably get a 337 approved by the FSDO for a non-TSO'd unit as long as it wasn't in the "T" area of the panel. One FSDO guy said I might need to label it "VFR only" and I'd have to promise not to do 135. In either case I'll end up having an electric backup AI for under $1500. That's less than the price of a backup electric vac pump installed about about the same price to put a Precise Flight in a Mooney (with California labor rates of $95/hr ) with twice the redundency. -Robert |
#2
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Robert M. Gary wrote:
After having both a vac pump failure and an AI failure (not on the same flight ) I decided its really time for a backup. I always consider my Mooney to be an "IFR anytime" type of plane, in that I consider it a solid IFR platform. When the vac pump goes out alarms starting sounding, my voice annunicator starting saying "check vac pressure" and the needle goes to 0. It's pretty obvious. I do a voluntary IPC every 6 months with a local DE and always do partial panel approaches so I'm as comfortable as you can be with that. A couple weeks ago I had my AI go out. WOW, that's another story!! The thing slowly rolled 30 degrees off and REMAINED RESPONSIVE!! When I banked, it banked, when I pitched, it piched. Figuring out that it was dead could be hard and it would be easy to miss it. I decided I need a back up and those vac backup systems are a waste of money(Precise Flight, electric vac, etc). After getting it back from overhaul my partner reported that it did it again! I called a couple gyro places and they said the vac AIs don't last very long because they have a stream of "dirty" air running through them. The electrics last much longer. So I'm getting an electric AI installed as my backup. I noticed that the non-TSO'd electric AIs are almost $1000 less than the TSO'd ones. I asked my mechanics and the FSDO and they said I could probably get a 337 approved by the FSDO for a non-TSO'd unit as long as it wasn't in the "T" area of the panel. One FSDO guy said I might need to label it "VFR only" and I'd have to promise not to do 135. In either case I'll end up having an electric backup AI for under $1500. That's less than the price of a backup electric vac pump installed about about the same price to put a Precise Flight in a Mooney (with California labor rates of $95/hr ) with twice the redundency. FWIW, I have an electric AI in my Mooney and I wouldn't do it again. It's expensive, failure prone, and too far out of my scan to be useful as a backup. I've had the Precise Flight system in a previous airplane, and it was OK, but has some drawbacks. Since it depends on the intake manifold as a vacuum source, the vacuum available is dependant on throttle setting. In order to maintain vacuum for the instruments, you may need a throttle setting that's not what you'd prefer. I now have the Aero-Advantage STCed dual-rotor vacuum pump and think it is overall the best solution. It offers more redundancy and more reliable backup for a reasonable price. http://www.aeroadvantage.com Including installation it will be less than your electric AI, and a better solution, IMO. Dave Remove SHIRT to reply directly. |
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#4
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Dave Butler wrote in message ...
I now have the Aero-Advantage STCed dual-rotor vacuum pump and think it is overall the best solution. It offers more redundancy and more reliable backup for a reasonable price. http://www.aeroadvantage.com Including installation it will be less than your electric AI, and a better solution, IMO. I'm not so worried about losing the vac. What I'm worried about is lossing the AI. BTW: What is the purpose of the dual rotor pump. When my pumps have gone out its always been because a vain got stuck and sheared off the pump shaft. My mechanic said that's how they usually fail. Wouldn't that kill both rotors? -Robert |
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#6
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Robert M. Gary wrote:
After having both a vac pump failure and an AI failure (not on the same flight ) I decided its really time for a backup. I had a similar revelation recently, after a challenging IPC at night and a quiet reflection on a AI that did fail one me, albeit on a nice day. Did lot of soul searching and decided to postpone a GPS upgrade in favor of some attitude information backup first. Dave Butler wrote: FWIW, I have an electric AI in my Mooney and I wouldn't do it again. It's expensive, failure prone, and too far out of my scan to be useful as a backup. Did you have a lot of problems with the electric AI ? I am also considering one (the dual pumps sound promising, but still don't back up the gyro...), so I am curious how they hold up (the RCA-26 series or the non-TSO'd Falcon, the AIM / Midcontinet stuff is just too expensive). I heard mixed reviews on the RC Allen, some people have had them for years without any problems and some claim they they don't hold up as well as quality vacuum gyros. Re Falcon, I strongly considered the possibility (337 or not), but with a custom tilt they are over $1100 (Chief), not *that* cheap considering a brand new RCA goes for $1650 at the discounters (like Spruce), factory tilt included and less paperwork hassle. Still, $500 is money, so if they are OK, might be worth considering. There seems to be very little info on them besides the manufacturer, unfortunately.... Thanks, Martin |
#7
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There are some non-TSO's EFIS systems around for under $2000! I saw
one at Oshkosh and was impressed! No moving parts, fully electronic. Check out http://www.dynonavionics.com Doug |
#8
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Robert M. Gary wrote:
I'm not so worried about losing the vac. What I'm worried about is lossing the AI. Am I missing something? How is installing a 2nd AI going to solve the problem of identifying an inaccurate indication? The old saying goes, "A man with one watch knows the time, a man with two watches is never sure." If you have two AIs and they disagree, how will you determine which one is correct? You will have to cross check against the DG and TC, same as you would if you had only one AI. Seems to me a better approach would be to practice cross-check in a simulator, where you can practice with an erratic AI rather than simply covering it up. Ross Oliver |
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If you have two AIs and they disagree, how will you determine which one is correct? You at least know one has gone south, and you can go PP. With only one AI, you could be leaning first. Jose -- (for Email, make the obvious changes in my address) |
#10
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Robert,
There was a recent article in Aviation Consumer about this (not sure if you subscribe): http://www.aviationconsumer.com/arch...ty/5307-1.html Among other things, they discuss: dual chamber vac with a backup gyro and PDA-style all electronic backups. If memory serves, a dual chamber vac with a backup gyro is not terribly expensive and probably wouldn't require fancy paperwork. I think they quote a price in the ballpark of $2000 for that solution. The PDA-style all electronic solution is a bit more pricey and wouldn't be panel mount. mark "Robert M. Gary" wrote in message om... After having both a vac pump failure and an AI failure (not on the same flight ) I decided its really time for a backup. I always consider my Mooney to be an "IFR anytime" type of plane, in that I consider it a solid IFR platform. When the vac pump goes out alarms starting sounding, my voice annunicator starting saying "check vac pressure" and the needle goes to 0. It's pretty obvious. I do a voluntary IPC every 6 months with a local DE and always do partial panel approaches so I'm as comfortable as you can be with that. A couple weeks ago I had my AI go out. WOW, that's another story!! The thing slowly rolled 30 degrees off and REMAINED RESPONSIVE!! When I banked, it banked, when I pitched, it piched. Figuring out that it was dead could be hard and it would be easy to miss it. I decided I need a back up and those vac backup systems are a waste of money(Precise Flight, electric vac, etc). After getting it back from overhaul my partner reported that it did it again! I called a couple gyro places and they said the vac AIs don't last very long because they have a stream of "dirty" air running through them. The electrics last much longer. So I'm getting an electric AI installed as my backup. I noticed that the non-TSO'd electric AIs are almost $1000 less than the TSO'd ones. I asked my mechanics and the FSDO and they said I could probably get a 337 approved by the FSDO for a non-TSO'd unit as long as it wasn't in the "T" area of the panel. One FSDO guy said I might need to label it "VFR only" and I'd have to promise not to do 135. In either case I'll end up having an electric backup AI for under $1500. That's less than the price of a backup electric vac pump installed about about the same price to put a Precise Flight in a Mooney (with California labor rates of $95/hr ) with twice the redundency. -Robert |
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