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Kellym
Joined: 10 Jan 2006
Posts: 1700
Location: Sun Lakes AZ
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 Posted: Mon Jul 31, 2006 8:13 am Post subject: Vacuum pumps and gyros (was: What upgrades |
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I've seen a fair number of alternator failures in a lot less than 500
hours, and/or regulator failures, over voltage failures, noise filter
failures.
If you fly a radial you expect oil. If you fly a flat four or six, you
don't. While wet pumps are reliable, they do waste oil, require
sizeable oil separators and are very costly compared to dry pumps. I
can easily buy 4-5 dry pumps for what a wet pump and oil separator
install costs. Vacuum pumps failing from sheared quill and unexpected
causes are relatively rare, and mean someone screwed up the install
and didn't clean the lines/replace the old cracked lines or otherwise
contaminated the suction side. If you do a proper install, failures
are rather rare. I really wasn't defending the use of a vacuum system
per se. I was pointing out that the most cost effective backup is
replacing T&B/TC with electric AI, or if you have space, just putting
in electric AI. Gives you true dual system, with only minor loss of
heading information if vacuum fails.
Quoting Brian Lloyd <brian-yak(at)lloyd.com>:
| Quote: |
On Jul 31, 2006, at 12:12 AM, Kelly McMullen wrote:
> You know, that claim is actually funny. You are touting the reliability
of a system that has passed 500 hours. If you had alternators that were
failing every 500 hours you would probably be really annoyed with their
poor quality. And if the alternator fails you still have the battery to
proved backup. There is no inherent backup with a vacuum system.
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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
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brian
Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA
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| Posted: Mon Jul 31, 2006 10:26 am Post subject: Vacuum pumps and gyros (was: What upgrades |
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On Jul , 26, at 2: PM, Kelly McMullen wrote:
| Quote: |
<kellym(at)aviating.com>
I've seen a fair number of alternator failures in a lot less than
5 hours, and/or regulator failures, over voltage failures, noise
filter failures.
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Sure they fail. I have seen engine failures at much less than TBO too
but, in general, alternators last longer than vacuum pumps by a wide
margin. And the rest of what I said, that there is an intrinsic
backup from the battery that doesn't exist with a vacuum pump, is
also true.
| Quote: | If you fly a radial you expect oil.
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Surprisingly, this is not necessarily true. I have seen dry radials.
(I used to own one.) When they are flinging oil everywhere it usually
means something needs to be tightened. Of course, flying
| Quote: | If you fly a flat four or six, you don't. While wet pumps are
reliable, they do waste oil,
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Well, no, not really. Sure some oil goes out the pump exhaust but it
is not a lot of oil. Let me put it this way -- I could not discern
the difference in oil consumption between wet and dry vacuum pumps.
The engine uses so much more than the vacuum pump does that you just
can't tell.
| Quote: | require sizeable oil separators
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It depends on your point of view. *I* don't think it requires an oil
separator but a lot of other people seem to think so.
| Quote: | and are very costly compared to dry pumps. I can easily buy 4-5 dry
pumps for what a wet pump and oil separator install costs.
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An overhauled wet pump is not all that expensive. It is certainly
worth considering if you have a vacuum system and your dry pump has
failed.
| Quote: | Vacuum pumps failing from sheared quill and unexpected causes are
relatively rare,
and mean someone screwed up the install and didn't clean the lines/
replace the old cracked lines or otherwise contaminated the suction
side. If you do a proper install, failures are rather rare.
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You should check with your local repair station if you think that is
true.
The truth of the matter is simple:
. A wet vacuum pump is more reliable than a dry vacuum pump.
2. An electrical system, almost ANY electrical system, is more
reliable than a vacuum system for powering gyros. The electrical
systems proposed by Electric Bob are so far more reliable than vacuum
pumps that they aren't even in the same universe.
| Quote: | I really wasn't defending the use of a vacuum system per se. I was
pointing out that the most cost effective backup is replacing T&B/
TC with electric AI, or if you have space, just putting in electric
AI. Gives you true dual system, with only minor loss of heading
information if vacuum fails.
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Or go to an all electric panel and have your no-single-point-of-
failure electrical system provide reliable power to your gyros too.
Fortunately OBAM aircraft owners have that option. Most of the new
aircraft are going to all-electric panels. They aren't going to the
trouble of getting them certified with the hidebound FAA just for
chuckles.
Brian Lloyd 6 Catterline Way
brian-yak AT lloyd DOT com Folsom, CA 956
+.96.67.2 (voice) +.27.92.788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
— Antoine de Saint-Exupéry
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery |
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