> =20 Naf, A few more things to check: 1. The maximum obtainable system pressure is set by the relief valves = inside the hydraulic pump. The relief valve protects all components from = over-pressure in case something causes the pump to run continuously or = thermal expansion etc. The relief valve should be set a few hundred psi = above the nominal operating pressure. I have tested our cylinders to over = 2000 psi. The pump is, however, capable of much more so the relief valve = needs to be set properly. 2. There are two paths for fluid to get past the piston: The main piston = seal and a sealing washer under the nut. Leaks past the main seal tend to = via scratches in the cylinder walls. These leaks can range in severity - = bleed down in minutes, hours or days. =20 Failure of the sealing washer is a bit more dramatic. It can flow a = relatively large amount of fluid and cause the pump to run continuously. = The sealing washers are probably missed during many rebuilds since they = are not visible upon initial disassembly of the cylinders and they are not = included in the seal kits from Lancair. =20 Chris Zavatson N91CZ 360 std. www.N91CZ.com --=__PartDDFF62FD.0__= Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Description: HTML

<<I= removed all hydraulic components and had my hydraulic shop at work check = out the switches and actuators. All good except hi pressure switch = was switching high off-scale. Nose gear actuator was allowing fluid = past the piston. I suspect that actuator was responsible for the = incident and that the switch was the root cause of the nose actuator = failure.>>

<<How did the nose gear gas strut (spring) check out - 100# of = force?>>

Naf,

A few more things to check:

1. The maximum obtainable system pressure is set by the relief = valves inside the hydraulic pump. The relief valve protects all = components from over-pressure in case something causes the pump to run = continuously or thermal expansion etc. The relief valve should be = set a few hundred psi above the nominal operating pressure. I = have tested our cylinders to over 2000 psi. The pump is, however, = capable of much more so the relief valve needs to be set properly.

2. There are two paths for fluid to get past the piston: = The main piston seal and a sealing washer under the nut. Leaks = past the main seal tend to via scratches in the cylinder walls. = These leaks can range in severity - bleed down in minutes, hours or = days.

Failure of the sealing washer is a bit more dramatic. It can = flow a relatively large amount of fluid and cause the pump to run = continuously. The sealing washers are probably missed during = many rebuilds since they are not visible upon initial disassembly of = the cylinders and they are not included in the seal kits from = Lancair.

Chris Zavatson

N91CZ

360 std.

www.N91CZ.com

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