Mystery with emergency gear extension

[Oscar Avalle]

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]

Oscar, when you rotate the handle in the cockpit, does the motor shaft turn?

 

[Oscar Avalle]

Oscar, when you rotate the handle in the cockpit, does the motor shaft turn?
 

No, it does not engage


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[Mooneymite]

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?

 

[Oscar Avalle]

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]

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-

[Oscar Avalle]

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]

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?

[Oscar Avalle]

It has not been used to retract, the shaft rotates it does not engage or as you say no longer"grabs"


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[carusoam]

Brass is a soft material and gets easily misshapen by harder SS materials. It is probably selected for it's lower friction and ease of manufacture.

Best regards,

-a-

[Mooneymite]

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.

 

[Mooneymite]

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.  

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

 

Edited November 15, 2016 by Mooneymite

[Oscar Avalle]

Yes very strange, the cable turns, but the gear does not reach far enough to grab the shaft. It looks as if the cable is too short ?


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[Mooneymite]

The cheap and easy first step would be to disconnect the flexible drive at both ends and make sure of its integrity.

 

http://www.mooney.com/en/sb/M20-190B.pdf

 

 

[Oscar Avalle]

Thank you!!! Will do and get back


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[TTaylor]

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.

[Cyril Gibb]

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.

 

[Oscar Avalle]

Yes that is the case. What did you do?


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[Cyril Gibb]

Clarences guys took it out (as part of the annual ITT servicing) and thoroughly cleaned and lubed.  Worked fine after.  Unfortunately there isn't any kind of boot to prevent stuff from accumulating in the mechanism.  Add a few years of hardened grease....

 

[Oscar Avalle]

Sorry to be so repetitive, but this is where the cable does not engage...

 

[Cyril Gibb]

Yup.... and it was the engagement lever just above the head of your arrow that was the problem.  It wasn't stuff in the splines that was the issue.  It was the gunk preventing the free movement of the little lever.

[carusoam]

The power of MS is always interesting!

Best regards,

-a-

[Oscar Avalle]

We are an amazing group! Thank you, I will report back on what is going on...

[Oscar Avalle]

We are an amazing group! Thank you, I will report back on what is going on...

Just heard back from the gear motor shop. Everything checked out well...so no explanation why the emergency gear extension cable is not connecting well...getting frustrated...


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[N201MKTurbo]

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.