Wolfgang,
The
‘failure to retract’ issue, to which you refer, sounds like a pump
configuration issue.
For example, the current pump sold by
Lancair for the 320/360/Legacy contains spool return springs. This configuration has the
potential to lock up due to thermal heating. This configuration is simply not
compatible with the design of the Lancair two-seat hydraulic systems.
With personnel turn-over at both companies,
neither side knows why the return springs were added. However, both Parker and Lancair
agree that a lock up on the ground is possible with the springs
installed. This lock-up has
been experienced by some, including the factory Legacy. It just has not been reported enough
to drive an engineering change at Lancair.
Parker
has graciously supplied parts to revert currently sold “CZZ” pumps back to
the original 320/360 configuration with respect to spool operation. I have been forwarding these parts
free of charge to anyone who needs them.
I applaud your ingenuity in devising your
circuit. Unfortunately your
energy seems to be a little misplaced. I would prefer to investigate
and fix the root cause of any out of the ordinary behavior-especially on an
airplane! If my engine
was burning a quart of oil per hour, the fix would not to design a
gadget that would pump oil from an onboard supply into the sump and
replenish the lost oil. The
solution, albeit painful in the short term, would be to open up
the engine, find and fix the problem and then fly like other
engines.
I understand that removing a pump, in
particular those mounted behind the baggage bulkhead is no fun. Poor access is a real deterrent for
any maintenance activity. That
is simply human nature. In the
grand scheme of things, it is a small price to pay.
My offer still stands to examine your
(Lorn’s) pump or any other that is able to lock-up both circuits. I have not yet come
across one that did not have an obvious cause-like the springs mentioned
above, so any such reported behavior of great interest to me and is worth
investigating.
Chris
Zavatson
N91CZ
360std
www.N91CZ.net
From: Wolfgang
<Wolfgang@MiCom.net>
To: lml@lancaironline.net
Sent: Wednesday, September 5, 2012 9:28
AM
Subject: [LML] Re:
Thermal influence on Hydraulic Pressure
Let's not forget this thermal influence causing
non-function can also happen in reverse. It has been reported that a thermal
a soak on the ground after a cold night can and has caused a failure to
retract after take off.
A while back I offered a solution of bumping
the pump automatically whenever both pressure switches, HI and LO, are open
due to high pressure. This would put the system back in normal
operation mode without the need for pilot intervention
Wolfgang