| With the dump valve open someone crawling under the plane could push up on the drag link collapsing the nose gear, perhaps crushing them. A rather expensive mouse trap. If the link is not over center, say due to a small piece of debris in the link, the nose gear will collapse when you open the dump valve. Bill H. If your IV is pressurized, make the header tank strong enough to resist maximum possible pressurization differential. A crushed header tank in flight could be messy. You could test it by pulling the equivalent suction pressure on the tank.
Eskesen <breskesen@comcast.net> wrote: To: lml@lancaironline.net
Date: Fri, 21 Mar 2008 17:58:38 -0400
From: "Eskesen" <breskesen@comcast.net>
Subject: [LML] Gear wouldn't come up, LNC2
Gerard, As Randy S points out, opening the dump valve merely equalizes the pressure on both sides. But, it's a much lower pressure and therefore allows the up pressure switch to stay open even when the fluid temperature has increased substantially. I shut down the engine, turn off the master, and then open the dump valve which I leave open while parked. Remember that the landing gear has an over center mechanism on each gear leg that locks the gear in the extended position. The gear stays locked until hydraulic pressure
is used to unlock the over center mechanism(s) at the beginning of the retract cycle. If you were to open the dump valve with the master switch on, the pump will run continuously but will build no pressure till the valve is closed. For those of us who occassionally have the pump not respond to the down switch while in flight, opening the dump valve momentarilly will reduce the hydraulic pressure that has built up during our flight through changing temperatures, thus allowing the pump to come on and extending the gear. Byron Eskesen
Regards, Bill Hannahan
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