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Mystery with emergency gear extension

Oscar Avalle
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Oscar Avalle Grand Master

Oscar Avalle

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I am hitting a wall with a problem I encountered during my annual. Neither Don, nor anybody else has been able to find a solution for it.

A while ago I had a problem with my landing gear motor and I engaged the manual emergency gear extension. The handle started to turn and I immediately disconnected the circuit breaker. The motor was send for overhaul and it has been working well.

Now during the annual I tried to use the emergency gear extension system. Although the handle and the cable did move as expected, it was never able to engage it to lower the gear manually. I send the motor assembly in, but it checked out well... so the cable seems to be ok, the motor too... so what is wrong?

Any ideas on how to solve it are welcome...

Thank you

Oscar

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Mooneymite Grand Master

Mooneymite

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Just now, Oscar Avalle said:


No, it does not engage
 

Okay, that's helpful.  So, there's a disconnect somewhere between the handle and the motor shaft.....

When you rotate the handle in the cockpit, does the output shaft to the flex-drive rotate?

 

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Oscar Avalle Grand Master

Oscar Avalle

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Okay, that's helpful.  So, there's a disconnect somewhere between the handle and the motor shaft.....
When you rotate the handle in the cockpit, does the output shaft to the flex-drive rotate?
 

Thank you! Yes it does rotate, but it seems that the shaft does not get to engage


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carusoam Grand Master

carusoam

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The weakness in the system is usually a brass piece that gets a small deformation that then blocks the entry of one part into the other...

Our MSer that has provided the best photos is Andrew, aka Hyett....

i believe this is related to no back clutch spring or whatever that thing is called.  :)

Best regards,

-a-

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Oscar Avalle Grand Master

Oscar Avalle

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The weakness in the system is usually a brass piece that gets a small deformation that then blocks the entry of one part into the other...
Our MSer that has provided the best photos is Andrew, aka Hyett....
i believe this is related to no back clutch spring or whatever that thing is called.  
Best regards,
-a-

Thank you! I will look for the pictures.


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Mooneymite Grand Master

Mooneymite

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Just now, Oscar Avalle said:


Thank you! Yes it does rotate, but it seems that the shaft does not get to engage
 

Okay, I'm getting confused.  Does the flexible shaft itself rotate?

What I'm working toward is that one end of the flexible shaft, or the other may have been damaged and no longer "grabs".

To the best of your knowledge, the emergency extension mechanism has never been used to retract the gear, correct?

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Mooneymite Grand Master

Mooneymite

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Just now, carusoam said:

.....i believe this is related to no back clutch spring or whatever that thing is called.  :)

Happily, the mighty C does not have that no-back spring.  The C's emergency extension system is pretty basic....a handle in the cockpit just turns the motor shaft.

 

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Mooneymite Grand Master

Mooneymite

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Oscar, from you description, it sounds like the worm gear may be the problem, but if that was so, it would not extend electrically!

Pretty strange that the gear extends electrically, but not when the motor shaft is turned mechanically.  :blink:

Looking at the pictures in the Service Bulletin might be helpful....

 

Edited by Mooneymite
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TTaylor Experienced

TTaylor

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Several years ago my manual extention would not work. We removed the gearbox where the flexible cable joins the electric drive and cleaned it in a chemical bath and replaced all the grease. The grease had become hard and limited the movement of the cable.

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Cyril Gibb Experienced

Cyril Gibb

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If your emergency gear actuator is the same as my F, the red lever that engages the mechanism pushes the splined end of the rotating cable into a splined female sleeve in the actuator.  On mine, the grease and accumulated crap from the previous owners inadequate maintenance was preventing the splines from engaging.

 

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  • 2 weeks later...
N201MKTurbo Grand Master

N201MKTurbo

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Ok, there are two splined shafts one on the motor and one on the flexible shaft. There is a coupling with interior splines that slides  on the spline of the flexible cable. There is a spring that pushes the coupling so it slides over the motor splined shaft coupling the flexible cable to the motor shaft. The lever on the disconnect mechanism has a fork that pushes on a flange on the splined coupling which compresses the spring and disconnects the flexable cable from the motor. 

To troubleshoot, have someone in the cockpit engage the emergency extension and move the crank back and forth 1/2 turn. Look at the rubber coupling between the motor and the gearbox, it should move with the handle. If it doesn't then the splines are not engaging. 

It only takes a slight burr on the coupling or the shaft to keep them from engaging. Small burrs can be fixed with a small file or a razor blade.

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