Manual Gear Extension Fail

[tcal780]

Hello All,

I wrapped up my transition training in my M20C and one of the last things we did was an emergency gear extension. After I engaged the lever and cranked, no luck. I felt winding feedback in the handle, it took some effort to crank, maybe 10-15 lbs of pressure (not like the crank wasn't connected to anything), and the gear up light never went out. Fortunately, the gear operated normally afterwards.

The bird is fresh out of annual (from the shop at the airport where the plane was previously based) and my gear actuator was repaired by lasar. Tomorrow, I plan to contact my local shop and schedule the repair, but my questions are:

1. Is the manual gear extension something that is regularly checked in an annual inspection?

2. Knowing the actuator was uninstalled/reinstalled, should the shop have at least verified the manual extension was operational at that time?

3. What is the likely cause?

 

Thanks,

Tcal

[0TreeLemur]

19 minutes ago, tcal780 said:

1. Is the manual gear extension something that is regularly checked in an annual inspection?

yes.

2. Knowing the actuator was uninstalled/reinstalled, should the shop have at least verified the manual extension was operational at that time?

yes.

3. What is the likely cause?

Good question.

 

[EricJ]

23 minutes ago, tcal780 said:

Hello All,

I wrapped up my transition training in my M20C and one of the last things we did was an emergency gear extension. After I engaged the lever and cranked, no luck. I felt winding feedback in the handle, it took some effort to crank, maybe 10-15 lbs of pressure (not like the crank wasn't connected to anything), and the gear up light never went out. Fortunately, the gear operated normally afterwards.

The bird is fresh out of annual (from the shop at the airport where the plane was previously based) and my gear actuator was repaired by lasar. Tomorrow, I plan to contact my local shop and schedule the repair, but my questions are:

1. Is the manual gear extension something that is regularly checked in an annual inspection?

Yes, it is a required inspection task to test the emergency gear extension during an annual inspection.

23 minutes ago, tcal780 said:

2. Knowing the actuator was uninstalled/reinstalled, should the shop have at least verified the manual extension was operational at that time?

Yes, if it was done during the annual.   Even if it wasn't it should be checked.   The maintenance manual should say what needs to be done.

23 minutes ago, tcal780 said:

3. What is the likely cause?

 

Thanks,

Tcal

Good question. 

 

Edited June 13, 2022 by EricJ

[cbarry]

I’m not a mechanic, but it sounds as if the engagement spline was in a bind when you the pushed the emergency engagement lever forward.  Did you try barely rocking the crank handle back and forth and confirm the engagement lever was full forward? Also, you could try disengaging the lever and then engaging it again to see if the binding is gone.

[Ron McBride]

Did you follow the Poh instructions, pull the breaker, engage the crank, then it takes about 50+ cranks. 
 

also, it is not recommended to practice this in the air, these units are fragile.  Have your mechanic put it on jacks, then practice. 
 

 

[Hank]

21 minutes ago, Ron McBride said:

Did you follow the Poh instructions, pull the breaker, engage the crank, then it takes about 50+ cranks. 
 

also, it is not recommended to practice this in the air, these units are fragile.  Have your mechanic put it on jacks, then practice. 

It's good to do it once in the air during transition training. 

On my C, it's 52 cranks. The one time I had to do it for real, I had a total electrical failure after dropping the gear. I knew exactly what to do, but because it had already started, it only went 12 turns. But the floor indicator was green.

Knowing what to do, and having done it, I knew it was not a big deal. The CFII beside me was worries and wanted the POH, I just leveled off and cranked as much as I could first, then pulled the Owners Manual from the seat back pocket and opened it to the Emergency Page.

Edited June 13, 2022 by Hank

[Ragsf15e]

Since the manual extension turns the electric motor for the normal extension system, and that was replaced at annual, I’m guessing they were definitely working on it. It’s a pretty simple system, so shouldn’t be hard to figure out once you pull the belly panels.

Did you pull the circuit breaker and follow the checklist?

[KSMooniac]

I bet the manual system was not rigged correctly when they worked on the actuator. It should've been checked during the maintenance and/or at annual. I'd bet a dollar your coupling spline is now toast, so your next step should be putting it on jacks and inspecting everything.

Maybe 7 years ago I bought the spline from LASAR so you might start there if you find yours failed.

Good luck

Sent from my LM-V405 using Tapatalk

[BDPetersen]

Interesting that it is 52 cranks on a Mooney, Bonanza, and C310. Sorry to hear the Mooney system is fragile.

[Guest]

A few possible fails here.  Something wrong in the maintenance, and in the flight training.  Your first manual gear extension for training should have been done in the shop on jacks.

Clarence

[Fly Boomer]

2 hours ago, M20Doc said:

Your first manual gear extension for training should have been done in the shop on jacks.

And the next manual extension too.

[tcal780]

I followed the POH. (Pull breaker, down switch, push lever forward, then crank)

Thanks for the responses. I will follow up!

[Ragsf15e]

55 minutes ago, tcal780 said:

I followed the POH. (Pull breaker, down switch, push lever forward, then crank)

Thanks for the responses. I will follow up!

While I agree that it would be better to do your first one in the shop on jacks, my first one was in my transition training too.  And it also went horribly wrong.  The “Mooney” cfi kind of guessed how to go through the exercise, and I didn’t know any better.  We followed the checklist and got the gear down, but there’s no checklist to get it back up.  We failed to disengage the manual crank and it spun real fast backwards when we engaged the motor up.  Could have destroyed my knee and destroyed the manual system.  I got lucky and no damage.

The Mooney manual backup system may not be perfect in every failure.  It seems most applicable to a loss of electrical power to the gear motor.  In that case, it works really well.  If somehow your electric motor is jammed/seized, the backup is likely useless.  I’m not saying that happens, but the manual system just manually actuates the primary system.

Let us know what you find out.

[FlySafe]

I second @KSMooniaccheck the rigging on the manual extension; it has to be exact. I have seen a few instances after annuals when it's been inspected/adjust, while dealing with the 2 reoccuring gear ADs, subsequent failures of the spline gear socket to engage.  Have inspected by your A&P asap, as it can be only partially engaged and simply rotating on the gear engagement shaft when the gear cycles causing damage ....personal experience, see pics (1st bad, 2nd good), LASAR has or did have part, good luck.  

k

[tcal780]

Great feedback.

Shop claims to have cycled the manual gear extension 3 times. Not like they'd admit it if they didn't.

I'm flying it back this Sunday morning (gear down). I'll stay there and observe while they pull it apart.

[Hank]

2 hours ago, tcal780 said:

I'm flying it back this Sunday morning (gear down). I'll stay there and observe while they pull it apart.

 Nothing like a slow flight below gear speed to make you appreciate your Mooney even more!

I had to do that when I took friends to lunch, and the lineman told me one of my nose gear doors was flapping. One of the arms had broken, so I flew home slowly, gear down, and ordered some parts--about half of the nose truss. Hope yours comes out better!

[carusoam]

Nice pics of the gear spline!

Hitting the electric gear switch with the Manual back-up system semi-engaged has caused this challenge several times…

The Preflight check list has been modified by several MSers to emphasize making sure the system is properly locked…

Thanks for sharing them…

Best regards,

-a-

[tcal780]

@FlySafe I see your photo of the mashed spline. I'm curious what the male end of that coupling looks like after this situation. Is it damaged also?

[KSMooniac]

15 hours ago, tcal780 said:

@FlySafe I see your photo of the mashed spline. I'm curious what the male end of that coupling looks like after this situation. Is it damaged also?

When mine failed, it looked exactly like the pics above, and the other end was just fine... Very likely intentionally harder than the coupler that is easy to replace.  That is good engineering, except for the single point of failure.

[FlySafe]

21 hours ago, tcal780 said:

I see your photo of the mashed spline. I'm curious what the male end of that coupling looks like after this situation. Is it damaged also?

Hi tcal78, similar to KSMooniac's experience, the male end looked fine.  And, as carusoam, mentioned, the fist step in my checklist upon entering the cabin is now to check the emergency extension handle position. I'm teachable especially when $$$ associated with the event  

[N201MKTurbo]

1 hour ago, FlySafe said:

Hi tcal78, similar to KSMooniac's experience, the male end looked fine.  And, as carusoam, mentioned, the fist step in my checklist upon entering the cabin is now to check the emergency extension handle position. I'm teachable especially when $$$ associated with the event  

I take a 15 inch piece of safety wire and twist loops in each end around a socket. Then I wrap it around the crank center and the lever knob shaft then twist a few twists in the wire like a twist tie. It makes absolutely sure that lever won't move and it is easy to get off if needed.

[tcal780]

Follow up:

Thankfully, the issue was only a piece of sheet metal binding the cable and preventing the spring from engaging the drive when the lever was engaged. You'll see in the pic exactly where. A little adjustment and a zip tie solved the problem.

Pretty windy on Sunday. It took me an hour to get there, gear down, with a 30kt tailwind. 1.0 hour return trip home with the gear up!

I'm just thrilled it was an easy fix.

[Fly Boomer]

On 6/20/2022 at 11:30 PM, tcal780 said:

the issue was only a piece of sheet metal binding the cable and preventing the spring from engaging the drive when the lever was engaged.

I don't understand.  The arrow points to a location where the sheath passes through a hole in the sheet metal.  As far as I know, the sheath is not supposed to move -- only the cable/wire inside the sheath.

[RobertGary1]

On 6/12/2022 at 7:18 PM, Ron McBride said:

Did you follow the Poh instructions, pull the breaker, engage the crank, then it takes about 50+ cranks. 
 

also, it is not recommended to practice this in the air, these units are fragile.  Have your mechanic put it on jacks, then practice. 
 

 

That’s likely the issue. Will work fine without an air load. If the splines are a little worn they may slip under load but work on the jacks 

[tcal780]

18 hours ago, Fly Boomer said:

I don't understand.  The arrow points to a location where the sheath passes through a hole in the sheet metal.  As far as I know, the sheath is not supposed to move -- only the cable/wire inside the sheath.

I thought the same thing when I put eyes on it. After all, the cable is affixed to the actuator, too.  Sure enough, after they secured the cable better the lever worked fine.

In retrospect, and in my opinion, I think the locking cable could use better/more lubrication, it seemed like the spring was struggling to engage it.

Edited June 23, 2022 by tcal780