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?