I thought that this (vibration) might be the problem and tried
various ways of tightening the fit (used rubber between the door and airframe
etc) but apparently ground observers say my door hangs completely open in
flight and sometimes I would hear a short cycle from the pump and the buzzing
would stop abruptly when it slammed shut. The current problem is that on
retracting the gear it doesn't close at all.
 
  I used to have the problem with back pressure in the down line..this
manifested as the nose gear door closing in 3 quick jerks as the pressure bled
off during retraction. I'm pretty certain the current problem commenced after
I replaced the valve assembly which solved problem number one (the jerky
closure). I wonder if the spool valve problem manifests itself in various
ways??? Do you have any

Gerhard,

 

If the nose gear door sequence valve is not adjusted properly, then all of these problems could occur.

 

1.  not closing or sometimes closing - depends on whether the nose gear actually trips the valve.

 

2.  intermittent could be because pressure leakage when the valve is just opened the weeest bit, the hi pressure bleeds down a bit (trying to close the door), pump runs, repeat this same sequence a few times until everything is finally done in.

 

Remember that the sequence valve is a defeated check valve.  Fluid can always run from OUT to IN as when the door opens and the fluid from the hi pressure side of the actuator runs back to the reservoir.  The fluid is not allowed to run from IN to OUT until the plunger is depressed, thus defeating the "check valve" function.

 

Scott Krueger