lml@lancaironline.net Mailing List Archive

Charley,

Lancair started adding return springs inside the spool valve for Legacy pumps in about 2005. One of the consequences of doing this is what you have observed in the hangar. You sort of have a 'get out of jail free' card in that your hydraulic system has a three-way valve. It doesn't prevent the lock-up. It just gives you a way out. Folks installing the 'Legacy' pump in 300 series plane with a two-way valve can get stuck. Fortunately the springs are easily removed and Parker has been providing the parts free-of-charge to reset pumps back to the pre-2005 configuration.

Chris

Chris Zavatson

N91CZ

360std. 1,400 hrs

http://www.n91cz.net/

From: Charles Brown <browncc1@verizon.net>
To: lml@lancaironline.net
Sent: Friday, January 25, 2013 11:07 PM
Subject: [LML] Re: Thermal influence on Hydraulic Pressure

This has happened to me even at the beginning of a flight, if the temps in the hangar have gone from cold on a previous day, to warm on flight day. I guess cold temps shrink the fluid and suck more from the reservoir into the lines, and when it warms, the pressure builds on both sides of the system, so that the "up" and "down" pressure switches are both open and the gear won't move until I pop the bleed valve.

Nasty when the gear won't retract just after blasting off into a low overcast.

Charley Brown

Legacy #299 200 hr

On Jan 25, 2013, at 7:23 AM, randy snarr wrote:

. I dont like having to open the dump valve but it is necessary once in a while especially when it is cold. The pressures on both sides of the system climb due to the engine heat and the gear sometimes will not move without dumping the pressure.