Message-ID: <19981109235310.10429.qmail@www04.netaddress.usa.net>
Date: Mon, 09 Nov 1998 23:53:10
From: Dan Schaefer <dfschaefer@usa.net>
To: lancair.list@olsusa.com
Subject: gear pressure bleed-down
Mime-Version: 1.0

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To Ed de Chazal, when you answered Angier Ames re: gear pressure bleed
-down, I don't think Angier was talking about bleed-down while 
retracted. Instead, I think some of the Glasair Gang has been spooking 
him about the bad things that will happen when, not if, his hydro 
pressure bleeds down while the gear is extended and on the ground.
To that, with a Lancair, the answer is "Nada" - but not for a Glasair.
They use hydro pressure to down-lock so if it ever goes away, the 
gear will collapse. I speak from eye-ball evidence of the guy in the 
hangar next to me - last year he had a hydro failure in his Glasair 
III, following which I honestly believe his prop was just a bit too 
short to be useful.

As you know, when the gear is up, it is held up by hydro pressure.
For you folks that haven't flown yet, or are just getting 
started, there is an exciting little happening that you WILL 
experience sooner or later. One that no one has probably thought to 
tell you about yet. This *fun* thing will happen at an unexpected 
moment while you are happily droning along being pretty smug about 
things. Just when you're at your most relaxed, all the electrical 
stuff on the panel goes "TWITCH!" accompanied by a subliminal "GRUNT!" 
 - GUARANTEED to get your attention and your heart rate up six 
or seven zillion beats! Depending on a lot of variables in a system 
that must have some leakage, the up-lock pressure can bleed down
enough to let the high-pressure limit switch kick in for just a pulse 
when it will immediately turn itself off again.

The pump starting up, particularly into an already high pressure, 
guarantees that it will pull a big current pulse and the results will
definitely get your attention! Hence the TWITCH! and GRUNT! In my 
plane, while on cruise, I'd see it about every 35-45 minutes. (That 
frequency was likely due to a sightly higher than normal high pressure
(up-side) leakage rate - around the threads of the junky, brass, gear 
dump-valve that came with the kit [subsequently replaced with a high 
quality valve]). Until I figured out what the H--- was going on, I
must say, I was a little spooked!

Not being too bright, I took the wife with me on a 2 1/2 hour flight 
before I had figured out what was going on. The "TWITCH!" and "GRUNT!"
did not escape her notice. As she's still of a mind that *real* 
airplanes are only entered from a carpeted walk directly from the 
first class lounge - and anything that happened on my little buzz-bomb
that was in any way unusual (meaning that I turned white and sweated
when it happened) was a BAD THING. Funny how the wife's insistance 
that I get her on the ground *now!* forces one to really think. Also
fortunately, I had caught the "Gear in transit" light flash at the 
same time as the TWITCH! 'n GRUNT! and I had the proverbial light 
flash over my head at the same time, and I figured it out. Not a 
moment too soon too! I really think she believed me when I casually 
turned and said "Oh! Don't worry about the TWITCH! 'n GRUNT!, that's 
just a 'normal little thing', keeps the gear tightly retracted so we 
don't slow down too much, and it's going to happen about every 35-40 
minutes". Since she didn't insist again that we land immediately, and
the TWITCH! 'n GRUNT! happened right on schedule 38 minutes later, I
got away with one. Of course, now that I've replaced the junky valve
with one that doesn't leak much at all, the T 'n G occurs only about
once in a four hour flight, if that. Now the wife wants to know why 
the T 'n G isn't happening any more and worries about it. Can't win!

Dan Schaefer
N235SP


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