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Dom,
I can confirm your observations!
Many years ago I dicussed this subject with NEICO and gave
them following explanation:
- when hydraulic pump is off it shut off the high and low
pressure lines too
- opening the free fall valve create a short way of the two
chambers of the hydraulic actuator
- problem is: the chamber capacity of the retracting is
smaller than the extending caused by the piston rod
- hydraulic fluid is almoust
incompressible
- now free fall of gear
- this cause a vacuum in the pusing sinde of the actuator
(too less fluid for chamber)
- the lowering gear has to work against this
vacuum
- the vacuum gradually disapear because of
air leakage through the o-rings
You can do the opposite test:
- when gear is down and locked
- open the free fall valve
- now try to push in the gear
-> you won´t be able to do so because now you are
working against the (incombressibel) hydraulic fluid!
Typical design error ... ;-(
Johannes
D-ESWS LNC2
I’d like to draw on the opinion
of listers regarding LNC2 gear free fall problem.
The main gear is slow to free
fall, and on the jacks (most likely in the air) the RMG won’t lock
in.
Slight pressure on the wheel
locks it in, which is handy if one wing walks upside down.
Disconnected the actuator strut
and it drops like a beauty and snaps into position.
I doubt the actuator struts are
the problem because both main gear have exhibited the same problem at the same
time. The LMG does eventually lock down on the jacks.
One thing I’ve noticed is the
NG is slower to lock down under normal extension than it usually does. Until
recently, it was always the first, and quick to lock down. Under free fall the
gas strut dives the NG down and locks as it should quite
quickly.
Wondered if anyone might have a
trouble shooting sequence I can draw upon.
Thanks
Dom Crain
VH-CZJ
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