Gary,
That is truly the simplest approach. The Parker pumps are in theory set up in the same way. It is just that the tripping pressure was set far too high (by a "non-adjustable" relief valve) to be useful for us.
On the ground it is not such a big deal since leaving the dump valve open will keep the entire system unpressurized. In-flight could really use a more appropriate setting to make use of the hardware already resident in the pump. Turns out not to be that hard to do. -just need to add a jam nut and adjust like the pressure relief valves on the pump side of the circuit.
Chris Zavatson
N91CZ
360std
From: Gary Casey <casey.gary@yahoo.com>
To: lml@lancaironline.net
Sent: Saturday, September 8, 2012 3:22 PM
Subject: [LML] Re: Thermal influence on Hydraulic Pressure
| I don't know much about the problem, but....I've owned a couple of retractible Cessnas and their approach, as well as Piper's was also to "dead-head" the pressure, in some cases just in the retracted position and in others both the up and down position. They had a relief valve that I assume would relieve the pressure caused by temperature increases. That was coupled with a pressure switch that would turn on the pump in case the pressure decayed, either from a temperature drop or from a leak. A very simple setup and I have never heard of a problem caused by that arrangement. One difference was that there was no gauge or warning switch that would let the pilot know that the pressure was rising. Just wondering, that's all...
Gary Casey
gear "down and welded" |