Gear problem

[skymstr02]

Sounds like you have an up lock switch that is losing its contact when the gear settles into the up locks, or a wire going to the switch is deteriorated.

[Hank]

Thanks. I have visually checked the main gear uplocks and all appears fine, the nose gear uplock is under an inspection panel that only be opened when the plane is on jacks. Can the switches be tested when the plane is on the ground or does the plane need to be on jacks? And to add to the confusion sometimes the gear works normally on the first try.

[skymstr02]

The panel on the belly behind the nose gear can be opened without the plane on jacks. Take the two tie rods from the aft door to the NLG loose, and swing the door towards the gear. This will expose the row of screws on the leading edge of the panel.

[WebMaster]

Would anyone be willing to take some pictures of the various limit switches, up locks, and adjustment points??
Since the landing gear is always an issue, I would gladly make up a web page for gear issues.

[Skymaster337B]

Switches are the usual suspects. However, I always start with the basics. Is the hydraulic fluid full? Since the gear seems to work after trying it 2 or 3 times it might be low of fluid...because the pressure has to be build-up to complete the uplock sequence even after the limit switches have made contact. The other possibility is air in the system too, and since it is a "self bleeding" system after 2 or 3 cycles any air will "bled" out thus allowing pressure to build up on the 2nd or 3rd try.

[Hank]

The level was checked and a little low. After filling with fluid the gear did the same thing on the up cycle - the gear would go up, light comes on, doors close but before the handle would go back to neutral the light goes out and the doors open. However on the next flight the gear operated normally. Tom Carr at CPA suggested a broken wire in the uplock circuit. So today the plane goes on jacks and the wires in the uplock circuit are flexed to see if any cause the light to go out and the uplock switches are tested. He said any break or loss of contact in that circuit would case the doors to open.

[Roger]

I am somewhat reluctant to mention this as there are a lot of A&P's here that probably know better, but I will merely advise what has worked for my like gear problems in the past.
a) Open the doors
b) Wipe all the switches off with a clean rag
c) Spray the switches with a degreasing compound
d) Blow air on the switches with an air compressor.
e) Wipe them off again
f) Spray them with WD40.



My experience has been that the switches are so sensitive that a bit of oil, grease, sand etc... has a tendancy to make them finicky. Keep them clean and lubricated, and it will potentially help with their operation.