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#11
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Bill Hale wrote:
The gyros will typically run for ~ 5 min, but they lose the erection function caused by the vacuum loss. You must have way better bearings than I do... or maybe you're measuring the time to when they stop spinning. They become useless for attitude control way before they stop spinning. Not sure what the 'erection function' is. I'm afraid to ask. |
#12
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Dave Butler wrote
Not sure what the 'erection function' is. I'm afraid to ask. Research pendulous vanes. Bob Moore |
#13
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Bob Moore wrote:
Research pendulous vanes. Thanks, Bob, I know what pendulous vanes are, but I was having trouble relating pendulous vanes to the context of lost vacuum due to engine stoppage. The poster wrote: The gyros will typically run for ~ 5 min, but they lose the erection function caused by the vacuum loss. |
#14
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Bob Moore wrote:
Dave Butler wrote Not sure what the 'erection function' is. I'm afraid to ask. Research pendulous vanes. Sort of gyroscopic viagra? |
#15
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On Wed, 13 Oct 2004 04:39:47 GMT, Matt Young
wrote: Ok, a curious question just popped in my mind. Say that one was flying IFR in a piston single, maybe a 172 or 182. While enroute, either in actual or above a cloud layer, the engine fails. Will the windmilling prop keep the vacuum pump going enough to make the AI and DG usuable during descent through the clouds, or will the gyros keep spinning fast enough long enough to make the vacuum pump irrelevant? Your 're going to get answers all over the spectrum, but my take would be it might happen, but don't count on it to save your bacon. IOW, I'd not count on them working, or staying accurate which is _far_worse_ than not working when you are in the clouds. There are many variables such as the actual engine, prop, and vacuum pump combination as well as best glide speed. Its been my experience (which may not be typical) that a wet pump will do better with the low RPM than the dry pump. This is assuming you still have RPM which with a catastrophic failure you probably won't. In my particular airplane which has a wet pump and a constant speed prop, once the instruments are spun up even vacuum at idle (which is well below the minimum) will keep the AI and DG working. The AI stays accurate. The DG will start precessing but slowly although it does hold well with a prolonged idle on the ground. Actually it's close to being in tolerance. With full vacuum I don't have to reset it during a 3 to 4 hour flight. So, I'd expect to see the vacuum instruments "on mine" hold for some time, but even knowing them as well as I do, I'd still depend on partial panel and consider any use out of the vacuum instruments a bonus. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com |
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