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Hard to say why, Chris - clearly you might think
insufficient torque of the nut/bolt when it was tightened.
- but, (yes, another Ed Anderson story) the
immediate cause of my 12 mile engine out glide was having a fuel fitting (flop
tube) nut come unscrewed inside the fuel tank after 160 hours of flight.
Now, I presume I simply did not tighten it sufficiently - but, I can't help but
wonder why it held on for 160 hours before coming loose. Could other
factors like temperature variation somehow cause the clamping forces to
slowly lessen? Wish I knew, but loctie should help.
From what I have heard is that due to the large surface
area of the main bearings that if lightly loaded even when oil pressure drops
near zero - the engine can continue to run (for a short period) without causing
damage. Now if under full throttle less time is available to catch
it. Hopefully that blinking alarm caught your attention shortly after
pressure fail below your alarm limit.
As others have already mentioned check the oil for metal
shavings - I like to pour the oil in a clear jar and let it set for a day or so
- normally the metal shavings (if any) will tend to settle to the bottom of the
jar. But, metal bearings babbit metal can become hot enough to deform/melt
without necessarily leaving a lot of metal in the oil. Also a magnet will
not attract babbit material - non-magnetic.
If I were disinclined to tear down the engine, I think I
would fix the problem, button it back up and then fire up the engine watching
the oil pressure very, very closely - if the oil pressure is within 2 psi of
what it was before at the various rpm points, particularly the lower rpm points
like idle, taxi, etc, then you are probably OK. If it varies by more
than 5 psi up or down, I would tear the engine down. Just my
viewpoint
Ed
Sent: Sunday, October 03, 2010 4:57 PM
Subject: [FlyRotary] Re: Smoking Gun -Loss of oil
pressure
I hope I have some luck cuz obviously I am not as good as I would have
liked to think :-/
I have not heard of this occurring either but hopefully my "solution" will
help the problem.
Sent from my iPhone 4
Chris, You must have been born lucky! It's just amazing that you've
found of all the things before getting airborne. I just hope you find
the one remaining item :) Regards, John On 10/3/2010 2:19
PM, Chris Barber wrote:
I removed the engine on Friday. Dropped the pan today, Sunday. The first thing I saw was the spring from the pressure control valve dangling from the bottom of the engine/engine mount. Then, as now expected, the pressure control valve sitting in the pan.
Well, to quote Mythbuster's "There's your problem.". So, now to re-read the install to see what I missed and perhaps add some Lock Tight.
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