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  Squat Switch Wiring Break - Potential Intermittent Gear Operation


Baron B58 owner Larry O., had a mysterious gear problem where his gear would retract partially then come to a complete stop. This problem could crop up in B55 and Bonanza aircraft with a squat switch mounted on one or both gear legs.


Conventional troubleshooting of the gear motor and switches came up with nothing unusual.


Here is what Larry found:


I had a gear wire break in the wheel well, pix attached. I'm posting because this is the second time this has happened (once on each gear)... so it could be common.


This is where the wire bundle comes from the down safety switch and goes back to a connector at the rear of the wheel well. (This is a mid 70s B58, but could be similar in other planes).


This is just a heads up. Perhaps hard to troubleshoot, to find out if a wire is "going to break", but if the wrapping is in poor shape, there's a though to take it off and examine the wires. Much easier to deal with on jacks than airborne.


The wire that broke in my case was the wire that goes from the safety switch to the gear motor. When the gear switch is put up, the safety switch closes and this wire provides power to raise the gear. There's two parts to the safety switch, and the other side opens when the plane lifts off and disconnects the gear up warning horn when the plane is on the ground.



Well, I had a well respected mechanic (actually two of them), mis- diagnose this issue by identifying the switch as being defective after crossing power from the horn circuit to the gear motor, thinking it was the gear circuit..... After I replaced the switch and it still didn't work, I dug into the wiring diagram and with some help from Stuart S. (another Baron owner/operator/IA), got to the right place.


Food for thought......


Here is the bend area that takes the most stress over the years. Bonanza and B55 Barons are similar in that the wiring must make a bend to go up into the wing from the squat switch. This bend takes all the flexing over the years of gear cycles.


B55 Baron owner, Lance F., offers some additional thoughts:


Note that the squat switch can only prevent the gear from retracting, if the switch fails or the wire breaks it will still go down. Also, if the switch is in the "weight on wheels" position with the gear selector in the UP position, the gear horn will sound but if a wire break stops the gear mid cycle the horn won't sound. It's also possible for a break in the same bundle to prevent the horn from working when the plane's on the ground with the gear selector in the UP position.


From time to time it might be a good idea to give this area of your wiring a close inspection for cracked insulation or wire breaking.


Check your specific wiring diagram for your SN airframe for the exact details of your squat switch wiring system.





The little rubber bootie protector on top of the switch actuator can deteriorate (left picture) and allow moisture and crud into the mechanism. Guess what happens next, yup, you've got a switch that no longer works! Check yours at annual to be sure it remains intact and functional. The picture on the right is the same bootie repaired with a rubber epoxy/sealant.


Check RAPID for this little gem. The OLD squat switch bootie is reported to be 35-361148 @ $22.95 on 6/17/2011. BUT, remember to check YOUR parts catalog for the PN for YOUR airplane.



Great find and pictures Larry!


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