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#21
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#22
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#23
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Jonathan Goodish wrote in message ...
In article , (Robert M. Gary) wrote: Let's see, I have 4 instruments in a basic IFR panel that can indicate the position of the wings. AI, DG, TC, and wet compass. If my AI starts to roll over 5 or 10 degrees and I level it, that's not going to put me in a death spiral, but I should notice heading changes regardless of what the TC is doing. If the ride is so rough that you can't obtain meaningful data from any of the other instruments, then you're not the guy I'd send to buy my lottery ticket. Its very common for me to be in actual conditions that are bouncy enough that the TC isn't going to do anything other than keep me upright. I'd be banking back and forth like a mad man as it flopped around. The compass is pretty useless, it just spins back and forth. That's the problem with most IFR, its usually very, very bouncy. If I had to pick between having the TC, DG, altimeter, and airspeed as my AI backup, or picking a second AI, I'd take the data from 4 instruments rather than one. But its not one, its two. If you look at the two AIs and they disagree you will say to yourself "Hmmm, something is wrong". The ability to say that is HUGE. A real AI failure is so mild that you probably would never notice. If just using the TC, DG and compass worked, you wouldn't hear about people dieing after partial panel situations. You wouldn't see big warnings on vac pumps. The airlines decided to get extra AIs and dump the TC a while ago. |
#24
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Dave Butler wrote in message ...
Mark Astley wrote: 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. Aviation Consumer's original article on the subject, written by Coy Jacobs, was pretty negative on the dual vacuum pump. It seems that Coy likes the items that he sells in his shop and tends to not like the items that are not sold in his shop. I've never been very happy with his objectivity. The whole scandal with the CorrosionX vs the competitor was a good reason for me to drop the subscriptions. Clearly he was going after the company that didn't want to let him resell their goo (in my opinion). -Robert |
#25
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Followup after talking to one of my partners: We're pretty sure it's an RC
Allen. It's been in a little longer than I thought, more like 12 years instead of 10. It's been repaired twice in the 12 years. The first time was relatively reasonable and cost a few hundred dollars. The second time was over a thousand and was called an 'overhaul'. The overhaul was done by Kelly Instruments. My partner's feeling is that the reliability and repair cost was no different from any typical gyro. The net is that maybe it's not as bad as I thought. The installation in my airplane is over on the copilot's side, so it's way out of my scan and therefore pretty much worthless. I'd go partial panel with the turn coordinator and mag compass before I'd try to use a gauge so far out of my scan. If you install an electric, be sure to put it where you can see it. Dave, thanks for the feedback ! Sounds like RCA, Kelly Inst. is the manufacturer of that brand. I bit the bullet and got one, will put it just right of the center stack for now, but I could also go into what is now the #2 CDI spot and move that to the right. That would look a bit funny, but may make for a much better cross-check. In any case, I'll definitely practice with it before considering it a solid backup. Martin |
#26
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I'm surprised no one has mentioned wet vacuum pumps. I'm considering a
wet pump when the current dry pump gives up the ghost, as it sounds like wet pumps are nearly bullet-proof. That said, I have been lucky in that I still have not had a vacuum pump go out on me. I have had several gyros fail though. -- --Ray Andraka, P.E. President, the Andraka Consulting Group, Inc. 401/884-7930 Fax 401/884-7950 http://www.andraka.com "They that give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -Benjamin Franklin, 1759 |
#27
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If you already have a few oil leaks, then the wet pump won't annoy you.
Those oil/air separators in the discharge are not perfect. ---JRC--- "Ray Andraka" wrote in message = ... I'm surprised no one has mentioned wet vacuum pumps. I'm considering = a wet pump when the current dry pump gives up the ghost, as it sounds = like wet pumps are nearly bullet-proof. That said, I have been lucky in = that I still have not had a vacuum pump go out on me. I have had several = gyros fail though. =20 |
#28
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Ray Andraka opined
I'm surprised no one has mentioned wet vacuum pumps. I'm considering a wet pump when the current dry pump gives up the ghost, as it sounds like wet pumps are nearly bullet-proof. That said, I have been lucky in that I still have not had a vacuum pump go out on me. I have had several gyros fail though. At one point I thought about replacing the dry pumps on a Twin Comanche with wet ones. Seems that you need to go through a bunch of STC or 337 field approval paper work to do the swap. So I dropped the idea. -ash Cthulhu for President! Why vote for a lesser evil? |
#29
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"Ash Wyllie" wrote in message = ... Ray Andraka opined =20 I'm surprised no one has mentioned wet vacuum pumps. I'm considering = a wet pump when the current dry pump gives up the ghost, as it sounds = like wet pumps are nearly bullet-proof. That said, I have been lucky in = that I still have not had a vacuum pump go out on me. I have had several = gyros fail though. =20 At one point I thought about replacing the dry pumps on a Twin = Comanche with wet ones. Seems that you need to go through a bunch of STC or 337 = field approval paper work to do the swap. So I dropped the idea. =20 =20 I don't know about Lycoming engines, but Continentals still have the oil = galleries under the mounting pads for the vacuum pumps. I know because I recently had to replace a leaking seal on one of my dry = pumps. Probably a simple 337 would suffice for Continentals. You'd just be changing back to the configuration they were originally = designed for. ---JRC--- |
#30
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Mine (a '65 model) originally had a wet pump, and I believe it is what is listed
on the TC. At one point I thought about replacing the dry pumps on a Twin Comanche with wet ones. Seems that you need to go through a bunch of STC or 337 field approval paper work to do the swap. So I dropped the idea. -ash Cthulhu for President! Why vote for a lesser evil? -- --Ray Andraka, P.E. President, the Andraka Consulting Group, Inc. 401/884-7930 Fax 401/884-7950 http://www.andraka.com "They that give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -Benjamin Franklin, 1759 |
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