Landing gear problem

[Shadrach]

14 minutes ago, steingar said:

When I'm flying I swing it at 80 mph.  It is quite easy, though you are correct, the most resistance is right where you said.  I've never had trouble swinging the gear, my problems were always in locking it.  Thankfully those are in the rear view mirror now.

I don't really use the ASI for retraction, but know from experience that 80MIAS just happens to be about how fast I am going after verifying positive rate and staring the swing. Raising the gear at VLO requires a bit more muscle. Glad you got it sorted!

[0TreeLemur]

Glad you got it solved too.  My a/c is on jacks- need to lube those up/down locks and the sliding collar.

[MinneMooney]

What do you use to lubricate the up lock? I am having problems getting mine to engage. No problem locking down, thankfully.

[carusoam]

Sounds like a different problem, MinneM...

Things That Get in the way of closing the gap are usually at the floor.  New rug?

Things that make it difficult to put the gear up, the air speed that occurs while waiting too long, convert speed to altitude for the gear movement... wind on the gear doors makes it challenging. More wind, more challenge...

lubing the gear lock block sounds pretty messy.

Any questions on this usually leads to putting the plane on jacks and operating the system while there is no wind.

Since you are looking, make sure both blocks are not worn to egg shapes... usually the down lock block shows wear...

PP thoughts only.

Best regards,

-a-

[M20F-1968]

I have never put any sort of lubrication on my J bar handle nor the down or up lock blocks.  My concern would be getting oil or silicone on the outside of the handle and the chisel shaped tip of the thumb lock.  The chisel shaped thumb lock end fits into a groove in the j bar handle.  I would think that a bit of friction (accomplished by not lubricating the handle) would add to keeping the chisel tip in place and locked.  That is, of course, assuming that handle fits well into the down lock block and the thumb lock springs into place.

I wonder if there are some slight differences in the manner the new down lock blocks are machined.  If they are geometrically out of spec. slightly, that could cause some problems.

John Breda

[Shadrach]

2 minutes ago, M20F-1968 said:

I have never put any sort of lubrication on my J bar handle nor the down or up lock blocks.  My concern would be getting oil or silicone on the outside of the handle and the chisel shaped tip of the thumb lock.  The chisel shaped thumb lock end fits into a groove in the j bar handle.  I would think that a bit of friction (accomplished by not lubricating the handle) would add to keeping the chisel tip in place and locked.  That is, of course, assuming that handle fits well into the down lock block and the thumb lock springs into place.

I wonder if there are some slight differences in the manner the new down lock blocks are machined.  If they are geometrically out of spec. slightly, that could cause some problems.

John Breda

+1 no external lube applied to my Johnson bar. Gear work flawlessly without it.

[steingar]

Guys, if my gear did nothing but work flawlessly this thread wouldn't exist.  I didn't like much spraying lube on the thing, but I really didn't like the thought of landing my airplane with the gear retracted.  If there's any question at all deliver your airplane to your local Mooney savvy mechanic and let them do their thing.  I think what they did on mine was 0.3 AMU, which is as cheap a squawk as I can remember seeing on an airplane.

[MinneMooney]

On 1/24/2019 at 4:50 PM, carusoam said:

Sounds like a different problem, MinneM...

Things That Get in the way of closing the gap are usually at the floor.  New rug?

Things that make it difficult to put the gear up, the air speed that occurs while waiting too long, convert speed to altitude for the gear movement... wind on the gear doors makes it challenging. More wind, more challenge...

lubing the gear lock block sounds pretty messy.

Any questions on this usually leads to putting the plane on jacks and operating the system while there is no wind.

Since you are looking, make sure both blocks are not worn to egg shapes... usually the down lock block shows wear...

PP thoughts only.

Best regards,

-a-

Anthony, this is in my new(to me) 1965 M20C, N5901Q, that I just purchased from the EAA. I’ve had it for about a week now.

The carpet is fairly new but doesn’t appear to be obstructing the J bar in any way. I do feel like there’s not much room for my fingers to fit between the handle and the carpet, so I have tried engaging the uplock with my fingers on top only without any more success.

The uplock block does appear to be oval on one the front side and perfectly round on the back. Not sure why that would make it difficult to engage the handle however. No matter how hard I bore down, I could not force that handle to slide into the uplock block. I finally was successful after half a dozen cycles down and up of the J bar. I wondered if anyone had tried a spray on dry lubricant on the inside of the unlock block. Or, should I use some emery cloth on the inside bore of the block.

FYI, the downlock was replaced not too long ago and has consistently worked fine. Also, there has been recent work where the landing gear were removed, refurbished, and reinstalled, so rigging could be contributing to the problem?

I may try to get it up on jacks at my A&P’s hangar so we can investigate this further if there isn’t an obvious fix.

I will try to post some pictures and tell a little about the history of this plane soon, since I find it very interesting.

Kim

 

[carusoam]

Great pics!

The block at the panel is showing the wear...

the stripe and the oval egg hole shape... are 50 years old...

the chromed steel handle sliding on the aluminum block removes a few atoms of aluminum each time...   there must be some real forces at work while on the ground.

Somebody once posted a bent j bar... so anything can be possible...

 

When my 65C got a new carpet, it needed a trim right at the base of the J bar...

that part is hiding from sight in your pic.

in your pic of the block on the floor... there is a bit of excess rug wave? Any excess might add to your challenge...

Being up on jacks, it should be easy to find what is in the way... or not aligning properly.

Altering a 50 year old design that was working recently... hold off on that for now...

When the j bar is up, you may see a pattern where the rug is getting squished...

PP thoughts only...

-a-

[MinneMooney]

Actually the block that is worn is the uplock on the floor. 

I will look to see if the carpet is obstructing anything.

Thanks.

[Sabremech]

34 minutes ago, MinneMooney said:

Actually the block that is worn is the uplock on the floor. 

I will look to see if the carpet is obstructing anything.

Thanks.

If you’re having trouble locking the gear down, make sure your J bar is not bent down towards the floor. Put a straight edge on it to check it. Mine took both hands to get it in the down lock until I found the bar bent. 

Talking with Dmax, the bar can get bent by being accidentally kicked out of the up lock in flight and slamming into the down lock unable to lock in. This will surprise you and will bend the J bar.

David

[MinneMooney]

Thanks. No problem locking down, just up. 

[RLCarter]

Sounds like it needs to be put on jacks to see what's going on. My guess is the one or several of the gear doors are too tight causing resistance 

[Sabremech]

36 minutes ago, MinneMooney said:

Thanks. No problem locking down, just up. 

That should be pretty easy to find on jacks.

[Hank]

1 hour ago, MinneMooney said:

Thanks. No problem locking down, just up. 

I think what David @Sabremech is saying is that a previous owner could have dislodged the Jbar from the floor (wheels up, Jbar down) in flight; when the Jbar slams into the uplock (wheels down, Jbar up), it can put a very slight bend in the Jbar, making it difficult to lock into the wheels up, Jbar down position.

Also, small wrinkles in the carpet have been known to have this effect, too.

But my C has electric gear so I have no personal knowledge. It just sounds like unclear communication is happening here--at least one of the three of us has static on the line, and it could easily be me.

[Sabremech]

35 minutes ago, Hank said:

I think what David @Sabremech is saying is that a previous owner could have dislodged the Jbar from the floor (wheels up, Jbar down) in flight; when the Jbar slams into the uplock (wheels down, Jbar up), it can put a very slight bend in the Jbar, making it difficult to lock into the wheels up, Jbar down position.

Also, small wrinkles in the carpet have been known to have this effect, too.

But my C has electric gear so I have no personal knowledge. It just sounds like unclear communication is happening here--at least one of the three of us has static on the line, and it could easily be me.

Hi Hank, 

Not quite right. When the J bar hits the down lock (J bar up) it bends the J bar aft away from the panel. This makes it much harder to push forward into the down lock block. In theory, the gear would be easier to put in the up lock on the floor with a bent J bar. The gear might be hanging out from the belly depending on the severity of the bend though. 

David

[carusoam]

So there’s another reason to get this figured out...

Avoid getting the experience of having the J bar rip through the cabin at cruise speeds...

Proof that The wind against the gear doors is trying hard to put the gear down...

It is quite scary. If it can bend a j bar, it can break anything else that gets in its way...

Best regards,

-a-

[Shadrach]

5 hours ago, Sabremech said:

If you’re having trouble locking the gear down, make sure your J bar is not bent down towards the floor. Put a straight edge on it to check it. Mine took both hands to get it in the down lock until I found the bar bent. 

Talking with Dmax, the bar can get bent by being accidentally kicked out of the up lock in flight and slamming into the down lock unable to lock in. This will surprise you and will bend the J bar.

David

When I was green in the plane many years ago, I failed to fully lock the gear in the up position on departure. Cruising along at 140KIAS the j-bar pops up between the seats and sort of wags back and forth between 55 and 75 degrees from the floor. It never came close to hitting the panel. I don’t know what king of airspeed it would require for Don’s scenario to take place, but if it could bend the bar, it could break an arm, wrist or finger. My singular experience is that an inadvertent gear drop at cruise speed is a benign event.

Edited January 28, 2019 by Shadrach

[Shadrach]

5 minutes ago, carusoam said:

So there’s another reason to get this figured out...

Avoid getting the experience of having the J bar rip through the cabin at cruise speeds...

Proof that The wind against the gear doors is trying hard to put the gear down...

It is quite scary. If it can bend a j bar, it can break anything else that gets in its way...

Best regards,

-a-

Did it ever happen to you?

[carusoam]

10 minutes ago, Shadrach said:

Did it ever happen to you?

Once... but probably not at cruise speed...

Never run experiments without asking first... MS is a much better resource than figuring things out on your own...

Some young engineer must have noticed the relationship between Jbar forces and airspeed... But didn’t take into account the relationship is probably not very linear...

Lets say it is pretty loud when a baseball bat comes through the cabin, and smacks the down lock block...

That young engineer, isn’t very young anymore... 

Best regards,

-a-

[Andy95W]

1 hour ago, Shadrach said:

Did it ever happen to you?

It happened to me, also.  When I was buying my current M20C with manual gear, my first Johnson Bar swing was with the previous (then current) owner.  It slipped out of my hand and went WHANG! into the down lock block and bounced back.  To his credit, the owner only said "you need to not let that happen".

When I disassembled the gear a few years ago, I checked it because of what Sabremech said happened to his.  Glad to say mine was straight.

[steingar]

Me too.  When I was first starting out I had the damn bar slip a bunch of times, several at cruise speed.  Did what the other fellow said, came up between the seats.  Startled the hell out of me, but never hit the panel.  Maybe in an E, or in a dive.

Still, my problem was stickiness in the down lock.  Once that got lubed up the problem went away.  Like I said, for me it was actually a pretty cheap squawk.

[MinneMooney]

Mine popped out at about 140 mph and stopped about half way. I was more concerned about damage to the gear doors. BTW, it was much harder to move the J bar at that speed. It wasn’t until we had slowed to about 120 mph that I was able to push it all the way down to the floor. 

[Shadrach]

This discussion interests me because some are describing a situation as a steel bar arching powerfully through the cockpit in a violently crashing into the down lock.  Others (myself included) have had the bar do a benign and gentle swing from the floor to the neutral midway point where the bar then stops and float back and forth a few degrees.  I was in high power cruise at 4500ft when it happened to me and there was nothing violent about it. The bar lightly grazed my elbow as it settled in place.   The idea that should the up lock fail you stand a chance of getting whacked with a steel pipe is scary if true.  It seems unlikely that some planes are gentle and some are violent.  From what I am reading, I think that the "bar to block smash" happens when the gear handle slips out of your hand in the 20 degrees of retraction at low speed.  Which does not seem like it would bend the bar.  NO disrespect to DMax, but I think a more plausable theory is that bars get bent when there is FOD in between the seats. The pilot unknowingly tries to force the gear down and the bar bends about the new defacto fulcrum (FOD).

[Marauder]

Sorry guys. This thread was ripe for the picking.

I had it happens to me once as well. Pretty violent. Lost grip on the little knobby and it slapped back into “up” position. Could have lost a finger nail.




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