Lancair IV
fellows!
I have the one and
only Lancair IV in Sweden. First flight on May 11 and now undergoing a 50 hour
testflight before final approvement by our EAA. Yes! in Sweden EAA
grants this permission and not the official swedish flightauthorities.
The testflying is a hard procedure so far. Every flight creates a new little
problem that has to be fixed before next testflight. So far only flew 16
hours of the 50 and soon arrives winter with snow and ice on tarmac and a
Lancair IV is totally impossible to taxi on ice.
One
day when opening the hangardoor whole floor was covered by hydraulic oil.
Flight before nothing was indicating to be faulty. After a
normal landing I taxied back
to the hangar. Nothing special was
discovered when the aircraft was pushed into the hangar. After inspection two days later we found that the left main
gear hydraulic cylinder was leaking. The
leakage caused to drain the oiltank of the hydralic
pump. The high pressure in the system from
the small pressuretank helped to blow out all the oil. If
the leakage had occured in the
air when bringing down the main gear during landing then the
left main gear should not have reached the looked position before
all oilpressure had disapeared.
When we began to check the reason for this
leakage we found a damaged sealingring on the piston rod. A closer look
to the sealingring shows four marks on it. Have a look at enclosed pic. We think that
this damage occured when the sealingring was mounted on the piston rod.
The reason for that is that the rod has a sharp square cutout at the end to
make it possible to turn the rod with a monkey wrench. We think that the
packing was damaged when pushing it over the square cutout when
mounting it on the rod. When removing the right hydralic
cylinder we found the same damage on the packing even there. It was
probably only a matter of time before this ring should begin to leak and this time maybe
the gear could not have been
loocked. Landing on the belly creates a
lot of damage. Assembling of these hydraulic
cylinders are presumably made by some phillipin who does not feel any
responsability for his job. Lancair in Redmond obviously does not check that
these very important parts are correct mounted.
The kit to this aircraft was delivered late
2000. If this bad mounting exist
on other hydraulic cylinders many accidents might occur or
maybe have already occured. How many of
you Lancair IV colleges have faced the same
problem?
It is time to publish a warning. Lancair technical department is advised of this
problem but I haven't so far got any reaction from
them.
This case
creates another question.
If the
hydraulic oil disappears during flight what kind of emergency procedure to you
have then? It is good to have a handdriven pump when the mainpump fails but to
what use if no oil in the system.
Last
question: On the pic you see the small red pressure cylinder that is mounted
in connection with the hydraulic oil system. Can anybody tell me when you need
the function of that little pressure tank. As I understood it the high
pressure in the small should be enough to lower and lock the gears if main
pump fails. But then you have your manual handle to pump down the gears with.
So what is the use for this pressure tank? It should be filled with high
pressure nitrogen but there is no info in kit instruction how high.
Anybody knows that?