M20 C uncommanded gear extension

[Urs_Wildermuth]

Folks, a question for you.

In recent days, we have had multiple cases where the landing gear of my M20C extended uncommanded, after the Johnson Bar escaped the uplock. This is not very funny when it happens, two cases were below 120mph and one at 140 mph.

First of all, is there any maintenance action necessary if the gear has extended above 120mph? We did a visual inspection after landing and everything seemed ok.

2ndly: What can cause this? We never had this in 7 years of ownership and now 3 times in a row. The last time I was PIC and I did retract the gear again and it held, so maybe it was not completely in. Are there still sources to get a better uplock? Maybe ours is too worn?

 

I always thought of the manual gear as being an assett, but right now I have my doubts.

[yvesg]

I had one such event a few months ago while flying formation with Ned. Same model, same year... Since then I pay more attention to the way I latch it after take off and it has not happened since. I believe it was not properly latched by inattention. Maybe lubbing this will help ease the mechanism in place?

Yves

[gsxrpilot]

22 minutes ago, Urs_Wildermuth said:

I always thought of the manual gear as being an asset

No, it still is. I wish I had manual gear on my 252.

But you can also expect that after 52 years of service, the hold down blocks can get worn. Check with LASAR for better than new replacements.

Those of us who have many hours with the manual gear, are fairly certain that main reason for the low gear speed limitation is the problem of controlling the Johnson bar with one arm. It won't hurt the gear.

[RLCarter]

I was talking to  Russell Stallings several years back and he had a rear seat pax hit the J-bar and unlock it at 150kts with no issues. I would definitely get it up on jacks and see what's up, the J-bar whacking you in the arm/elbow wouldn't feel good at all

Edited May 12, 2017 by RLCarter

[Wildhorsesracing]

I have tried to lower my gear a couple of times when I was still above 120 and realize the speed factor because it is so hard to do when I am going too fast.  When you think about it, the landing gear is designed to take a direct hit with the ground at between 60 and 80 mph, so being lowered into the airstream at 120+ is a non event to it's structure.  The gear doors on the other hand... 

[Sabremech]

This is what we believe caused the J-Bar in mine to be bent. Inadvertent release in flight and slamming forward into the downlock. Definitely caused me issues later with getting the gear in the down position with one hand until I discovered the cause. Might want to check the J-bar for straightness. 

David

[carusoam]

Take a picture of the up-lock block to see if it is wearing like the down-lock block does.

Early on in ownership I intentionally released the gear at ever increasing airspeeds. It goes from hard to put the gear down to easy. Then goes on to too easy and flat out dangerous as the jbar swings through the cabin...

There is a limit to where the release of the gear at speed no longer makes a lot of sense.

Other things like carpet, pens, and seat belts can get in the way of locking up properly.

M20C PP ideas that come to mind...

Best regards,

-a-

Edited May 12, 2017 by carusoam

[Ned Gravel]

4 hours ago, yvesg said:

I had one such event a few months ago while flying formation with Ned. Same model, same year... Since then I pay more attention to the way I latch it after take off and it has not happened since. I believe it was not properly latched by inattention. Maybe lubbing this will help ease the mechanism in place?

Yves

One of the things Yves and I learned from this incident is that an uncommanded gear drop is not sufficient reason for the wingman to call "blind" and then peel off to do a 360 and then catch up.  Catching up takes another 10 minutes or so.  

That was my call at the time and we have decided that should such happen again, the wingman will simply slow down (and drop about 40 feet) to match the lead's speed (it will have to be quick without the wingman deploying their own speed brakes - gear) but is it doable.  

[Boilermonkey]

I've had it happen while training in an M20C where I didn't get the bar all the way to the floor and in the block.   I use the same "thumbnail check" for the up and down position.  I should not be able to put my thumbnail between the block and the collar of the bar. 

[MBDiagMan]

Very educational thread!

I am surprised though that the bar coming out of the block would keep going all the way to the gear extended position.  It is a break over center type linkage and seems to require a little pull once out of the gear retracted block on the floor in order to extend the gear.  I will be paying more attention though to ensure that the bar is fully locked when on the floor.  I don't want that bar whacking Sandy's elbow.  I am not too excited about experience it hitting my elbow either.

[rbridges]

I guess if it has enough momentum, it could hit the block. I typically release it and keep enough hand pressure on it at the halfway point where it rests to rotate my grip to lock it. 

Btw, I thought the speed limitation was for the gear doors. Someone at my airport wrecked his front doors by dropping gear at high speed in his ovation. 

[Boilermonkey]

Better down than up though!

[gsxrpilot]

3 hours ago, rbridges said:

Btw, I thought the speed limitation was for the gear doors. Someone at my airport wrecked his front doors by dropping gear at high speed in his ovation. 

The gear speeds on the electric gear Mooney's are much higher.  I do believe that if you exceed THOSE gear speeds you risk wrecking the doors.

But with the manual gear Mooney, my belief is that you could drop the gear at up to electric gear speeds without damaging any doors. But the lower speed is because of needing to control the swing of the Johnson bar.  That is just my speculation, but it makes sense to my engineering mind. 

Please insert @carusoam's standard list of disclaimers here... it's just my opinion.

[rbridges]

26 minutes ago, gsxrpilot said:

The gear speeds on the electric gear Mooney's are much higher.  I do believe that if you exceed THOSE gear speeds you risk wrecking the doors.

But with the manual gear Mooney, my belief is that you could drop the gear at up to electric gear speeds without damaging any doors. But the lower speed is because of needing to control the swing of the Johnson bar.  That is just my speculation, but it makes sense to my engineering mind. 

Please insert @carusoam's standard list of disclaimers here... it's just my opinion.

makes sense to me, too.  You can tell a huge difference over just a few knots when trying to retract the gear.

 

no worries, carusoam would still approve.

[1964-M20E]

I have had this happen once before.  When raising the gear make sure it is firmly in the block.  Also if it is not at least on mine I can feel the trim whel on the jbar handle.

[Urs_Wildermuth]

Thanks guys!

This is pretty much what I thought.

The thought of hitting the downlock in an uncommanded release is outright scary, but I wonder how that happened. In the event I had, the lever never got higher than my tigh and the gear stayed there, right in transit about 50% between up and down. I immediately pulled the throttle back and kept the nose up to get the speed down and then initally put the gear all the way down and locked first, then, after a short assessment, put it back up again at about 80 mph. What I did notice however was a quite pronounced nose down pitch movement, the moment the gear released which the AP could not counter initially.

Wondering how to include this in our abnormal checklist.

Uncommanded gear extension

- Speed ....................... reduce to below 120 mph

- Gear .........................  down and lock

- Situation ..................  assess

If no damage visible and airplane flies normally

- Gear .........................   as required

- Consider following abnormal Landing Gear Indication Procedure

If abnormal behaviour encountered or damage evident

- Landing gear............... keep down and locked

Follow abnormal Landing Gear Indication Procedure

 

 

[Hank]

The downpitch is not surprising, the gear added a lot of drag on the bottom of the plane. Being only halfway down, it was a higher drag configuration than you usually see, plus the higher speed also made for much more drag (like lift, drag is proportional to speed).

It's probably a good idea to jack the plane and swing the gear a couple of times. This will let you check the Up Block and the Down Block that the Jbar locks into, as well as how the gear doors close.

After several collapses, people began checking the aluminum Down blocks, and many were replaced. You may be spotting similar wear on the Up block. Another owner reported a similar event. Isn't it fun to be on the leading edge of a problem? But it may have been just not engaged properly, thus the recommendation to check the block.

Please check everything and report back. Sounds like you were lucky the Jbar only came up halfway and didn't smack any arms, elbows, etc. Your luck may not hold the next time this happens . . . . . .

[gsxrpilot]

I don't think a checklist item is warranted. Sometimes shit happens and you just react to it. You reacted properly By the time you pull out a checklist on this one, you're several steps behind.

[Chocks]

Just remember, just like a door coming open in flight, your gear - just like the door - without force, will only partially deploy and be flexible into the wind.

No damage issues at higher speed that I can think of, as long as you're not attempting to push the gear into a fixed down position. Re-retract the gear and slow normally then extend and verify proper deployment of the gear. Good to go.

 

Just get the locking mech checked.

 

 

Sent from my iPhone using Tapatalk

 

[M20FTraveler]

12 hours ago, "Chocks" said:

Just remember, just like a door coming open in flight, your gear - just like the door - without force, will only partially deploy and be flexible into the wind.

This happened to me yesterday, but as I was less than 5nm from the airport I bled off the speed to 120 and locked the gear down.  That was after a 60nm trip when that happened.  Wife not pleased, but at least it didn't hit her upon release.  I will inspect the floor block. 

[RLCarter]

When on the jacks, verify that the handle engages fully into the block on the floor and the one under the panel as well. I don't have a lot of time (>50hrs) with a J-bar but I have to pay attention or I will unbuckle one or both front seatbelts (shoulder harness)

[mooniac15u]

On May 12, 2017 at 9:02 AM, gsxrpilot said:

No, it still is. I wish I had manual gear on my 252.

But you can also expect that after 52 years of service, the hold down blocks can get worn. Check with LASAR for better than new replacements.

Those of us who have many hours with the manual gear, are fairly certain that main reason for the low gear speed limitation is the problem of controlling the Johnson bar with one arm. It won't hurt the gear.

Didn't your old C suffer a gear collapse recently?  Did they find a good explanation for that incident?

Maybe the consequences of high speed extensions aren't immediately obvious. 

[gsxrpilot]

It did, but I haven't gotten a complete explanation. It wasn't my plane at the time. Don Maxwell has said that there have been a couple of these lately. He might have a good explanation.

[mooniac15u]

If @Sabremech is right and an inadvertent release of the gear generates enough force to bend a Johnson bar then it seems like there would also be some strong loads on the rest of the retraction system. 

[Sabremech]

1 hour ago, mooniac15u said:

If @Sabremech is right and an inadvertent release of the gear generates enough force to bend a Johnson bar then it seems like there would also be some strong loads on the rest of the retraction system. 

Maybe not. The Johnson bar is a long arm and not that heavy a wall tubing. It has some beef where it's attached to the cross shaft under the floor.