Squat Switch

[markejackson02]

Is the squat switch on the main landing gear normally closed or open on the ground?  I attached a link to a picture of the switch.  This is a 1976 M20J, early, serial #48.

 

I would have guessed that the switch was pressed closed on the ground.  It might be set up this way so a bounce on the taxi doesn't unload the switch resulting in inadvertant retraction.

 

Took the plane up for a test flight after a new engine was installed and the gear didn't retract.  Rather than fart around with the override swtich, selected gear down and landed.  The plane has been sitting for seven years.  Is there any recommended cleaning for the switch?

 

http://tinypic.com/m/i1ack6/4

 

Mark Jackson

 

[TTaylor]

There is a wiring diagram from my 75 F in my album. If the plane was sitting for seven years it is likely the doughnuts and not the switch. It is a common problem, especially in cold weather. Replacing the doughnuts will likely be required. The override switch should work in the meantime.

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[Marauder]

Mark - the picture shows the squat switch in the normal position on the ground. As Tim mentions, once airborne, the expansion of the gear donuts will allow the plate to contact the switch, enabling retraction.

On an early 76, you may not have this override switch:

[markejackson02]

I do have the override switch.  Going to try that on jacks and see if the switch closes.  Sounds like new shock donuts are in order.

[Marauder]

There is a date code stamped on the donuts so you should be able to tell how old they are. Mine were replaced in 1989 and again this past Spring. I did have problems back in the early 90s with really cold weather and the switch not activating. I had the override switch installed. So... Even with fairly "fresh" donuts I was still getting the fault. When I moved to a warmer climate, the problem wasn't very frequent -- that is until late last year and almost every flight I had to use the override switch. The new donuts cured it and I also noticed my plane sat a little higher. Sent from my iPad using Tapatalk

[jetdriven]

Glue a 1/8" piece of silicone baffle material to the arm where it contacts the squat switch.

[markejackson02]

I was able to use the override switch this weekend.  

 

The donuts will need to be replaced but at $200 a pop, that will have to wait another few months.  Hopefully warmer weather will cause them to expand.

[Marauder]

I was able to use the override switch this weekend.

The donuts will need to be replaced but at $200 a pop, that will have to wait another few months. Hopefully warmer weather will cause them to expand.

Donuts should be around $100/each. Others recently had their donuts replaced and can tell you where to get them. Good to hear the override work. How old are the donuts? Also, keep in mind, it could still be a faulty squat switch, but if your plane sat that long, the donuts are probably pretty bad.

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[TTaylor]

Glad to see the plane flying. South West Texas Aviation has a full set of 11 for $1023.

 

http://www.swta.net/monthlyspecial.html