brian
Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA
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 Posted: Mon Jul 31, 2006 3:09 am Post subject: Vacuum pumps and gyros (was: What upgrades are possible on a |
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On Jul 31, 2006, at 12:12 AM, Kelly McMullen wrote:
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<kellym(at)aviating.com>
Rapco and Tempest both offer that warranty on dry pumps. I wouldn't
touch a wet pump, I don't want an oil soaked belly and I don't have
room for a triple stage separator.
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There are worse things than oil on the belly ... like vacuum pump
failure. But then again, you probably have not lived with a radial
engine (otherwise known as the automatic airframe lubrication
system). I guess I accept a well-lubricated airframe as more or less
normal. Just remember, an oil-soaked airframe is less likely to
corrode. 
| Quote: | I'm over 500 hours on my current Rapco pump now..and on my plane it
drives a retractable step, and wing leveler system as well as the
gyros.
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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.
Engines that go to TBO rarely fail catastrophically. They have
problems but they keep working. Surprisingly most gyros fail
gradually too. Vacuum pumps fail, jam, shear their couplings, and
become inert hunks of junk with no warning. (I know, someone is going
to point out that dry pumps may produce more graphite at the output
before they fail but hey, who looks at that and can really tell if it
is more or less.) Now consider the consequences for many pilots when
two of their three gyros stop working in IFR conditions. I wonder
which is more likely to be survivable under IFR conditions: engine
failure or gyro failure? (And we can argue about that too but the
fact that it is arguable says something, don't you think?)
If I were starting from scratch on an airplane there is no way I
would include a vacuum system. Where I would have a vacuum pump I can
have a second source of electrical power. I can use that power not
only for my gyros but also for lights, radios, etc. So I end up with
a backup power source that can be used with all my devices. Also,
wire is smaller, lighter, and easier to route than a vacuum hose. I'm
sorry but to argue the merits of air-powered gyros strikes me as just
plain silly. The only reason to keep air powered gyros is because the
FAA won't let you change. (And that is telling also.)
I know, someone is going to jump in here and tell me that air-powered
gyros are less expensive. I know they are. But if you are going to
fly IFR your life depends more on the health of your gyros than on
just about anything else. If you are worried about the cost then get
a cheaper GPS or nav-com. Don't skimp on your gyros.
Brian Lloyd 361 Catterline Way
brian-yak AT lloyd DOT com Folsom, CA 95630
+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-Exupéry
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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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