Gear Up Limit Switches

[MichiganMooney]

Where are the gear up limit switches located on my Mooney 201?  What do they look like?

[jetdriven]

The gear up and gear down limit switches are located next to the right main retract tube under the floor.  The long ones that go from the main bellcrank to a 90 degree bellcrank at the rear of the rear belly panel. The tab that depresses the switch to cutoff the motor are mounted on the tube itself.   This is a multi-step process to adjust this from the service manual, and its really critical to get the proper up and down preload.

[MichiganMooney]

So you can't see the switches without removing panels?

 

When it is very cold, my gear retracts and stops in a position that appears to be full up.  (It doesn't strain so I'm assuming that it is stopped by the normal switch).  Unfortunately, the gear still shows as unsafe on the panel and it sounds a beeping warning.  If I recycle the gear after a few minutes of flight, it works fine.  This regularly happens when it is cold (below 10 degrees).  My thought is that it might be some type of switch that is frozen on one of the gear.  Does this make sense?  If so, where would that be.  If not, what is the problem?

[Marauder]

So you can't see the switches without removing panels?

When it is very cold, my gear retracts and stops in a position that appears to be full up. (It doesn't strain so I'm assuming that it is stopped by the normal switch). Unfortunately, the gear still shows as unsafe on the panel and it sounds a beeping warning. If I recycle the gear after a few minutes of flight, it works fine. This regularly happens when it is cold (below 10 degrees). My thought is that it might be some type of switch that is frozen on one of the gear. Does this make sense? If so, where would that be. If not, what is the problem?

What year Mooney? My 75F had this problem and it was related to the donuts getting old and not fully expanding in cold weather. I installed the override switch because on really cold days, it still may do it.

[Marauder]

BTW -- the switch involved is the squat switch. This is on older Mooneys. The newer ones use an airspeed switch.

[jetdriven]

Ours is starting to do that too. Ten years ago, Mooney installed a cold weather kit on ours to cure it, but its back only below 40 degrees.  I have also heard its the donuts not expanding enough.

[MichiganMooney]

_{I have a '77 M20J.  I don't think that I have a squat switch because the gear retracts fine, the airplane just doesn't know that it is fully retracted.  The motor stops, but the indicator still shows "Gear Unsafe".  Would a sensor that determines the gear position not work because of frozen donuts?}

[jetdriven]

I'm pretty sure you have a squat switch. We do. If the donuts don't clans enough to trip the squat switch it shuts the motor off.

_{I have a '77 M20J. I don't think that I have a squat switch because the gear retracts fine, the airplane just doesn't know that it is fully retracted. The motor stops, but the indicator still shows "Gear Unsafe". Would a sensor that determines the gear position not work because of frozen donuts?}

I'm pretty sure you have a squat switch. We do. If the donuts don't expand enough to trip the squat switch it shuts the motor off.

[N201MKTurbo]

I have a 77 201 and it has a squat switch.

The limit switch is a double throw switch it has normally closed and normally open contacts. The normally closed contacts stop the gear motor. The normally open contacts light the green light.

It is possible for one set of contacts to fail and the other set to work.

I would clean the switch with contact cleaner or tri flo.

[Marauder]

_{I have a '77 M20J.  I don't think that I have a squat switch because the gear retracts fine, the airplane just doesn't know that it is fully retracted.  The motor stops, but the indicator still shows "Gear Unsafe".  Would a sensor that determines the gear position not work because of frozen donuts?}

 

When you say the gear is "up" what reference are you using? The floor indicator?  

 

The squat switch is there to prevent accidental gear retraction on the ground. With the weight of the plane on the donuts, the squat switch is not contacted thus preventing the gear motor from engaging. On take-off, the weight is off the donuts and they expand contacting the squat switch and allowing the motor to operate. The failure mode of my squat switch not getting activated is exactly how you described. If the gear is not up and the squat has not been activated, you would get the beeping sound you mention and a gear unsafe light.

 

Do you have one of these on your panel?

 

[MichiganMooney]

No, I don't have one of those buttons.

 

If it was a squat switch problem, wouldn't the gear fail to retract?  I hear and feel the gear retract for the normal length of time.  When I recycle, I can hear and feel the gear extend.  Would a non-functioning squat switch allow the gear to go up but not indicate that the gear is fully up?

[Marauder]

If the squat switch is not activated once airborne, the gear will not retract, the unsafe gear light will come on and you will get an alarm sound -- at least that is what my 75 does and it should be similar to your 77. I have a hard time hearing my gear transit up. I'm surprised you can hear your's. That is why I asked if the floor indicator shows the gear is up. If you are certain it is up, then the problem is in the limit switches. The approach to correcting those were described above. The switch pictured was not standard until later J models. There was a service bulletin that allowed retrofits on older electric gear and I had it installed to deal with extremely cold weather ops where the gear would not retract.

[MichiganMooney]

I have noise cancelling headsets.  Perhaps that is why I can hear it.

 

Can I damage my gear if follow my current protocol of raising the gear and they recycling after a few minutes?  The gear motor isn't straining and shuts off at the proper time.