Adam,

Are you running the Stock Lancair gear system or are you using your gear system ?

Do you have the first generation pump or the high capacity one ?

From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Adam Molny
Sent: Monday, April 16, 2012 7:14 AM
To: lml@lancaironline.net
Subject: [LML] Excessive down hydraulic pressure

On my fourth test flight I tested the normal and emergency gear extension/retraction and everything worked fine. My first landing attempt resulted in a go-around due to gusty winds. When I extended the gear again on downwind nothing happened. After a few seconds of head-scratching I momentarily cracked the dump valve. That fixed the problem and the landing was uneventful (if a bit firm). http://www.youtube.com/watch?v=fo1qnhBuqS8

The attached JPG file shows the up and down hydraulic pressure readings throughout the flight. The x-axis is time, with the flight beginning at 20:32Z and ending at 21:12Z. You can see the gear retraction tests beginning around 20:43 and 3500' altitude. Notice that after the last test the down pressure remains around 500psi for about 90 seconds even though the gear is retracted. The up pressure fluctuates a bit then the down pressure drops to near zero. 

The bottom graph is a closer view of the landing sequence. The go-around occurs at 21:05Z. When I retracted the gear the up pressure went to 950psi as expected, but the down pressure fluctuated around 500psi. This kept the down pressure switch open, preventing gear extension.

Does anyone have an idea as to what's causing the pressure buildup on the down side? 

Thanks,

Adam Molny

N181AM 6.1hrs hobbs time