Return-Path: Received: from [65.33.87.175] (account ) by logan.com (CommuniGate Pro WebUser 4.0.5) with HTTP id 2001476 for ; Tue, 28 Jan 2003 08:38:54 -0500 From: "Marvin Kaye" Subject: Re: [LML] Re: LNC2-320 To: lml X-Mailer: CommuniGate Pro Web Mailer v.4.0.5 Date: Tue, 28 Jan 2003 08:38:54 -0500 Message-ID: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format="flowed" Content-Transfer-Encoding: 8bit Posted for "Christopher Zavatson" : George, Robert, I have experienced the same thing twice in my 750 hours. I also heard about the theory of a slow leak from the high to low side while in-flight, thus pressurizing the low side enough to trip the switch. At first this sounds quite reasonable, but I have been puzzling over two questions. First, if enough pressure bleeds of the high side to bring the low side up to 500 psi why didn't the high side have to cycle at least once some time during the flight. (Which it didn't in my case) The second question deals with the inner workings of the pump itself. While the up side is pressurized, the spool valve opens a back pressure circuit to dump the extra rod volume as the cylinders retract. With this circuit engaged the max pressure achievable in the low pressure side is 150 psi, the setting of the back pressure relief valve. I did not have pressure gauges installed at the time. They would have come in handy for diagnosing this event. I did, however, have momentary by-pass switches for both high and low pressure circuits. A quick push of the button sent the pump off and running. If it ever happens again, I will glance at the gauges before doing anything. Chris Zavatson N91CZ L360 std >>>This event as described has happened to me many times over the eight years and almost 900 hrs. with my airplane. I attribute it to a very slight leakage through the gear dump valve from the gear up pressure to the down side, and just enough to push open the gear down pressure switch. <<<