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<< Lancair Builders' Mail List >>
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To all Lancair IV builders and drivers
I am the builder that submitted the report of a problem to Ross at Lancair.
To their credit, they responded with the directive within one day. The
problem that we encountered did not result in any incident or accident as the
problem was encountered during gear cycle testing.
I am posting this report to let everyone know just how serious this problem
was and is if you have this particular filter in your return line. When I
assembled the system all lines were blown out with filtered shop air just
prior to the lines being screwed to their fittings. All fittings were kept
covered immediately after being installed into the manifold or hydraulic
cylinders. All cylinders had their plugs in place until their fittings were
installed. In other words I was very careful to keep dirt out of the system.
The hydraulic fluid that I bought came from an almost new 50 Gal drum at my
friendly FBO.
When I did my initial gear testing about 6 months ago the system seemed to
work perfect. After about 20 or so cycles I noticed that the pump was
cycling on and off and the gear was moving slower than it had. At that time
I thought that it was a low battery. I stopped the tests and went on to work
on other stuff.
Recently Brad Simmons came to Detroit to help me hang the engine and install
the cowl. One other thing that I wanted help with was to fix kinked brake
lines where they exit the trunion so we needed to once again cycle the gear.
As soon as we started cycling the gear we noticed that the gear was moving
slower than it should and the pump was cycling on and off every few seconds.
As the cycle tests continued the problem got worse and worse until the whole
system was locked and I mean Locked. The main and nose gear were half way
down. The flaps would not work and the hand pump was locked in place. A
gorilla could not move it.
I called Ross at Lancair and reported the problem. He said that the return
line had to be plugged some where and suggester a trouble shooting procedure
to isolate where the system was plugged. We followed his procedure and found
that the filter was completely plugged. I removed disassembled the filter
and did not find any evidence of visible dirt or crud but the filter element
felt gritty. I then put the filter back together without the filter element
or spring and the hydraulic system worked normal.
Since I was very careful when assembling the system and was not able to find
any visible dirt in the filter, I for one will not be reinstalling the guts
in my filter until we have some of bypass. A filter may me a good thing, But
not at the expense of a CATASTROPHIC Failure where the gear can be stuck half
way and no emergency procedure can get it down.
Tom Byrnes
Lancair N54TB
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LML website: http://www.olsusa.com/mkaye/maillist.html
LML Builders' Bookstore: http://www.buildersbooks.com/lancair
Please send your photos and drawings to marvkaye@olsusa.com.
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