Author Topic: Landing gear locking pin  (Read 1710 times)

Dan Rhinehart

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Landing gear locking pin
« on: September 27, 2015, 03:53:18 PM »
Hi all,

I have been working on my wings and have been trying to determine how much play/clearance the down lock pin in the landing gear should have.

I realize that too loose and the gear legs have too much play (side to side) and too tight of a clearance and the locking pin might not slide in.

Any thoughts?

Tim Lunceford

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Re: Landing gear locking pin
« Reply #1 on: September 28, 2015, 02:32:23 PM »
Dan,  I am in the middle of repairing/adjusting the gear on my daughter Cadet after a close call a couple of weeks ago.  Fortunately the pilot was persistent in getting the gear selector to engage and was able to engage the lock pins, landing without mishap.  Investigating I discovered that the left push tube was bend slightly where the threaded link exits the tube. I am replacing the links and installing rod ends.  I believe that had the holes in the top of the gear legs not been slightly elongated horizontally the pins would not have engaged.  I will measure the bore of the holes tonight.  I will also try and measure the amount of side to side play in my gear.   Tim

Tim Lunceford

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Re: Landing gear locking pin
« Reply #2 on: September 28, 2015, 06:55:47 PM »
Dan,  here is a picture of the push tube.  Bottom one is from the left side.

Tim Lunceford

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Re: Landing gear locking pin
« Reply #3 on: October 05, 2015, 01:00:00 PM »
I completed the installation of the new landing gear links this weekend.  Attached is a picture, they work very well with no clearance issues.  In order to determine the side to side play of the strut with the gear extended and the lock pins in place I disconnected the push tube to the lock pin bell-crank. Using the horizontal centerline at the end of the axle as the reference measured 1/8th of an inch side to side of play.  This seems to work very well on my installation.  By moving the gear leg slightly and manipulating the lock pin with my hand I could feel the correct position for the gear leg making it easy to adjust the landing gear push tube to the correct length.  Remember that this is all done on the right side with the left disconnected.  Once the right side was working correctly I readjusted the gear box stop screw and completed the assembly of the left side.  The gear now works very smoothly and with the gear extended while on the jacks the lock pins slip into place using the gear selector lever without any effort at all.  I might mention that previous to this incident the gear had work fine for 150 hours.  I have not determined what might have caused the old link to bend.  We have gear doors installed and I suspect that the additional stress caused by the doors resulted in the links giving a little over time until the right side reached a point that it deflected enough to create a larger bend.  Once this happened the lock pin would be misaligned and would malfunctioned.  I expect that the new links because of the added stiffness will resolve this issue.

Bill Poynter

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Re: Landing gear locking pin
« Reply #4 on: October 06, 2015, 09:08:15 AM »
I think the gear doors could have played a part in bending the link.  Another cause can be the C spring taking a set and not fully extending the gear.  This can result in the wheel rubbing the outer edge of the wheel well when retracted.  Forcing the wheel into the wheel well will definitely bend the linkage.  Guess how I know?

Tim Lunceford

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Re: Landing gear locking pin
« Reply #5 on: October 06, 2015, 11:46:06 AM »
Thanks Bill,  in my first two post I stated that the left link was bent.  It was actually the right side.  I guess I was thinking upside down and backward, nothing new for me.  Anyway I am sure you are aware that the right side leads the left and therefore is the first to be stressed.  Mark Penner has been following along and was kind enough to point out my error.