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Gerard,
I wonder if your problem is not with the hydraulics at all and is the door itself. There has been a long history of people having buzzing noises coming from their nose gear doors at higher speeds. The problem in this case has been that the belly is slightly curved (front to rear) but the door itself tends to be straight. If you retract the gear while on jacks and look at the nose gear door it will appear to be fully closed and held tightly by the hydraulic cylinder. However, test how tight the fit is at the trailing edge of the nose door. I bet it isn't even touching the fuselage or, if it is, it is quite a loose fit.
When I built my 320 I had heard about this problem and some people resolved it by making the door out of AL and inducing a curve into it. I went ahead with the glass door but built it with a slight curve and haven't yet had any buzzing sounds. I also remember some folks mentioning that they had the problem and then induced a curve in the rear edge of the door (behind the hinge line) with heat. This solved the problem for a while until the door started to straighten out again.
So, get it up on jacks and check it out. You may be able to bend your door (this should be a quick test, anyway) to solve the problem or you may want to fabricate a new door.
Best of luck!
Dan Olsen
N320DK - 150hrs
Fort Collins, CO
Larry, have been trying for ages to get the damn thing (nose gear door) to close properly. I replaced the valve assembly some time ago but the spool valve orientation was never verified as correct so I still have to do this as it apparently can produce a weak retraction although my guage is still reading 1500 psi on the up side.
From memory the problem first manifested itself shortly after the valve assembly was replaced, as a buzzing noise from outside, which I eventually (through the process of elimination and ground observers) tracked to the nose gear door not closing and thus catching the airflow at higher airspeeds. All leaks have been fixed (cylinders replaced and sequence valves replaced) which appeard to temporarily correct the problem. This was short lived however. ANother possibilty is perhaps tiny bits of hose breaking off and blocking the spool valve. My hose is over 10 years old..am sure there are better qualitiy availabe other the the original lancair issue stuff (circa 1990) which I'm told wasn't that great to begin with.
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Gerard O Connell
Melbourne, Australia
VH-LPD (LNC2)
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