Gear Doors will not close

[Cliff Dickehut]

My 1971 337F landing gear work with no problem, however we are having trouble getting the gear doors to close. Flew it yesterday and everything worked fine on takeoff and initial gear retraction. The doors closed just fine. When on desent to land the gear came down, locked, and got the green light, but the doors would not close. Several cycles produced the same results. The doors would not close.

I know some of you have had this problem. Looking for some help.

Yours for Christ,
Cliff:

[Skymaster337B]

Check hyd levels.

[Kim Geyer]

You might want to check the micro switch on the power pack it controls the door valve when the gear handle returns to the neutral position

[jchronic]

Both good suggestions, but follow Skymaster 337B's first (start simple). Had the same problem a few years back on a leased airplane that had a slow hydraulic leak.

Joe

[Ernie Martin]

This is NOT likely to be the issue, but if the above suggestions and other efforts fail to find the problem, check your speed when lowering and retracting the gear. Notice that it worked fine on retraction (when you are climbing and tend to be at a slower speed) but the doors failed to close on your descent, when you tend to have a higher speed.

If you look at the open doors -- especially the rear ones -- they are BIG and act like a small parachute. I'm thinking that if the powerpack is weak, it will work fine while you climb because of your lower speed, and it will lower the gear on descent, but it might be struggling trying to close the doors on your faster descent. I bring my speed down to under 130 MPH to drop the gear.

Again, follow all other suggestions first, but check this if all others fail.

Ernie

[Cliff Dickehut]

I will check everything you guys suggested. We replaced all of the hydraulic hoses and then hooked up a mule and did many cycles to get all of the air out. We are replacing the micro switch now that controls the doors. I will also slow to under 130 mph before cycling to see if the lower speed helps.

Thanks again everyone.

[jchronic]

And to riff a little on the point Ernie makes, I make it an operating practice to always slow when able to 110-120 mph before throwing flaps or gear out. I rarely see any reason to extend them at higher speeds...and these airframes and gear doors and associated mechanisms ain't getting any younger.

Joe

[Cliff Dickehut]

Thanks to all that had suggestions. We replaced the micro switch located under the panel right above the pilot's left knee. This switch controls the gear doors opening and closing. After replacing the switch the doors were still not working properly. Finally my mechanic bent the small metal arm that activates the push button on the switch. We are now getting good depression of the switch button and everything works great.

Thanks again to all that had ideas.

Yours for Christ,
Cliff