Richard,

Write or call me off-line and I’ll go through the details with you, but the basic theory of operation is that the flap cylinder has pressure applied to both the extend and retract sides when the flap control lever is in the up position. The flaps are held up/retracted in this situation because the piston surface area inside the flap operating cylinder is less (by the cross section of the operating rod) on the extend side than on the retract side. This causes the flaps to retract when normal pressure is applied to the hydraulic system. The flaps are extended by venting/dumping the pressure to the larger side of the cylinder, causing it to move the other direction.

Lancair provides an adjustable valve to control the rate of extension, and it is useful. I installed an additional valve in the “retract” side of the cylinder (stock item from McMaster Carr) that free-flows in one flow direction and is adjustable in the other. This allows me to set both the extend and retract speed to approximately 4 seconds each way. In the “stock” configuration, my flaps would retract in about one second—fast enough to cause difficulty in controlling the pitching moments during takeoff/go around.

Hope this helps…

Bob Pastusek

N437RP @ 90 hours