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Of course there's a pressure spike. Standard in all
hydraulic systems.
That's what happens when you start pumping fluid
faster than the inertia of the gear can follow.
Think about it
. . . when you start to push your car you have to
apply a lot of pressure
. . . but less pressure to keep it
rolling.
So the pressure spike can open up the switch
. . . fine
. . . then the pressure gets relieved as the gear
starts to move
. . . and the switch closes again
. . . and the motor runs again
. . . until the real end of stroke makes the
pressure go high and stay hi holding the pressure switch open.
This is a non-problem. . . . let it go
already.
Wolfgang
----- Original Message -----
Sent: Thursday, May 15, 2014 7:33
AM
Subject: Hydraulic Pressure Spike
Video
Using my iPhone I took a video of my pressure gauges while extending my
gear on a flight today. It is starting to warm up out
here. We're not cooking yet, but it is enough to start observing
the hydraulic pressure spike which was the subject of a previous LML
thread.
It was a bit bumpy on downwind, but the gauges are still clearly visible
in the video.
The high pressure circuit was just a hair under 1,500 psi when gear-down
was selected. One can hear the pump fire up and release the gear,
The high side pressure begins to drop and then the spike immediately hits the
low side. It reached 450 psi in this clip. If the spike reaches the low
side pressure switch setting, the pump solenoid will open and the pump will
shut down. I have my low side pressure switch set to 800 psi which has
proven to be high enough to avoid any gear hesitations and/or extension
failures.
Chris Zavatson
N91CZ
360std
www.N91CZ.net
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