Landing gear problem M20J

[N201JG]

I've had a 77 M20J since December.  Yesterday, when I retracted the gear, the gear unsafe light stayed illuminated.  I tried to lower the gear and nothing.  There was no circuit breaker pop and no other indication that anything electrical was going on.  After doing a couple of fly-by's to determine that the gear was retracted, or at least mostly retracted, I climbed out and did the emergency extension without issue and made probably the nicest landing in my life.  On the ground, the people who were watching the two passes I made with the gear still retracted had a couple slightly different versions.  One said the gear looked like it may have been not fully retracted; the other said it was fully retracted.  The plane was performing as if they were retracted on the initial climb out.

After speaking with the guy who does my maintenance he said it was safe to fly and to see if it retracted on the next flight over to his airport.  It did not move.  That landing went fine but nearly as pretty as the previous one.  Training note to myself - always pretend you don't know if the gear is locked when you land.

I've looked through the other forums which have many different causes.  Obviously we are going to jack it up and see what the problem is.  The gear unsafe light leads me to believe that the gear was not fully retracted, but may have been very close where there wasn't any noticeable drop in performance.  The guys who I was communicating to on the ground after I did the emergency extension told me that I should keep turning the handle after the green light came on.  Please don't blast me for this.  At the time I didn't know that was a no-no and my mechanic wasn't happy that I did that.  I've seen in another forum that over-cranking can cause it to get bound up to a point the electric system won't retract it.  The breaker didn't pop or anything on the second flight.  Nothing happened. 

I'm thinking/hoping that maybe I have a loose wire somewhere or there is something with the switch.  I was recently messing around with some avionics in the vicinity of the gear switch.  It's flown without issue since then but it's possible I inadvertently loosened something there.   If it turns out to be the motor, can anyone recommend a good overhaul/repair/exchange option for that?  

Thanks!

Ryan  

[KSMooniac]

I wouldn't fly it again until you open the belly and inspect everything. Look for bent retract tubes, dirty limit switches, broken/loose wires and terminals, damaged gear doors, etc. Also check behind the panel if you were working there. You should perform some retraction cycles on jacks too until you're convinced everything is nominal.

Many years ago my gear motor failed and a shop in CA overhauled it... Maybe George's Electric? I also have a 77 J. Fast forward a few more years and we caught a failed emergency extension spline at annual! Rigging had slipped and the teeth for chewed-up rendering it unusable. Had the motor failed in that condition it would have been a gear-up landing. Be thankful yours worked.

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[N201MKTurbo]

If it won't move in either direction, that points to the motor itself. I had that happen once and one of the brushes fell out. I hope your repair is as cheap as mine was,

[N201JG]

Thanks for the input.  Everything external looks good as far as the gear itself.  The switch is fine.  We are going to jack it up and look in the belly later this week.  Hopefully just a bad connection somewhere.  The gear unsafe light is still bugging me.  I got a few more opinions from the people who saw the whole ordeal and they are confident the gear was completely retracted.  

[carusoam]

There isn’t any digital magic in the system…

relays, position switches, airspeed or squat switch, motor…

Know what you have for a gear unsafe switch…. Squat vs airspeed… one is easier to check than the other…

airspeed switches get old… and get OH’d

Squat switches are temperature sensitive… and it just got warm…

 

If squat..  how old are the donuts?

-a-

[Yetti]

Lube the gear really well.   pull the actuator apart and lube it.    While you are there with open panels lube the u joints and chain in the trim.   It is amazing what quality maintenance and a little lube will do for parts that move.

[KSMooniac]

You should have a squat switch on the left MLG. I suspect if it were balky the gear would not retract at all, but worth a look and cleaning if needed.

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[EricJ]

3 hours ago, N201JG said:

Thanks for the input.  Everything external looks good as far as the gear itself.  The switch is fine.  We are going to jack it up and look in the belly later this week.  Hopefully just a bad connection somewhere.  The gear unsafe light is still bugging me.  I got a few more opinions from the people who saw the whole ordeal and they are confident the gear was completely retracted.  

The gear unsafe light just means that it hasn't closed the up-limit travel switch, and the switch failing could be the problem or something preventing the gear from retracting completely.   

Getting it on jacks with the belly open and a chance to look at everything should reveal all, I'd think.

 

[Ragsf15e]

Since the gear doors don’t fully cover the wheels when the gear is up, it’s very easy for people to think the gear are partially down when looking up at a flyby.  I’ve had the same ground report from the tower when my gear were up and locked.

[N201JG]

4 hours ago, EricJ said:

The gear unsafe light just means that it hasn't closed the up-limit travel switch, and the switch failing could be the problem or something preventing the gear from retracting completely.   

Getting it on jacks with the belly open and a chance to look at everything should reveal all, I'd think.

 

That’s what I think happened.  There are some canvas-like covers on the inner side of the gear gear doors that aren’t in great condition as I inspected today.  They may have had the ability to block the gear from being fully retracted to the limit switch even if it was just a bit off.  I thought that would cause the breaker to go if the motor was still working to raise the gear, or maybe the overload just toasted the motor.  It’s all speculation I guess until we get a good look on the inside.  I appreciate the comments and I’ll let you know what I find out.

[carusoam]

Rat socks are designed to not get in the way of the function of the gear…

They are good to get replaced if needed…

Getting the plane up on jacks and seeing how everything works is a great educational tool as well…

Take video and pics…

Best regards,

-a-

[N201JG]

1 minute ago, carusoam said:

Rat socks are designed to not get in the way of the function of the gear…

They are good to get replaced if needed…

Getting the plane up on jacks and seeing how everything works is a great educational tool as well…

Take video and pics…

Best regards,

-a-

I agree.  I’m too embarrassed to show the condition of mine.  I have little doubt these shredded pieces of fabric caused the initial retract problem.  I’m also not sure if I reset the emergency gear extension handle and lock correctly.  I’ve read that doing it improperly could result in the electric system being disabled until reset correctly.

[carusoam]

2 minutes ago, N201JG said:

I agree.  I’m too embarrassed to show the condition of mine.  I have little doubt these shredded pieces of fabric caused the initial retract problem.  I’m also not sure if I reset the emergency gear extension handle and lock correctly.  I’ve read that doing it improperly could result in the electric system being disabled until reset correctly.

Having the e-gear partially enabled while the normal gear is operating… causes destruction of a brass gear used by both systems…  misery ensues…

 

Have your check list set up to make sure the E-gear is stowed…. Extra important with back seaters…. They don’t know if they have accidentally kicked the device…

So… while up on jacks… review the E-gear procedures and see how well it works…

PP thoughts only, not a mechanic…

Best regards,

-a-

[N201JG]

Mine has the crank on the left of the pilot and it worked well.  I took a couple of pictures today after I removed the belly pan.  There is wire that is coming from the up limit switch that is cut.  Another picture shows that the gear down line from the gear motor is in pretty bad shape.  I’m trying to come up with a scenario how this could have caused my issues.  I couldn’t find the other side of the disconnected wire.

[carusoam]

See if @M20Doc can lend an eye… (landing gear wiring challenge… half figured out.)

Best regards,

-a-

[N201JG]

I have a little more information from the professionals and am looking for a second/third opinion.  I have two mechanics who have seen this and they have very different views on the problem.  Both of them have been really good in the past with my other airplanes so I am by no means trying to second guess them.  The inspection revealed that the right main gear tube was bowed pretty badly.  It is the one that has the contacts with the limit switches.  I wish I had a picture but I've seen similar pictures on the site when researching this.  It's the tube that goes from the actuator down toward the tail.  One guy is saying that you can just bend it back.  The other is saying it needs to be replaced and this is the cause of all my gear shenanigans from a couple weeks ago.

I'm all for replacing the part (560244-501) if I can find one, and that is the plan.  Both guys agree the rigging is off and that probably caused the bowing.  I'm still having difficulty seeing how this could have caused my problems.  One of the guys thinks the wire issues I took pictures of wouldn't have caused this problem.  That begs the question why I would have a wire just hanging around in there not connected to anything coming from the up limit switch...  

Someone tell me where we could be wrong on this.  The bowed tube caused the gear retraction to not hit the up limit switch which caused the gear unsafe warning.  The breaker didn't pop or anything during this retraction.  I should add that I flew the plane the day before and had no issues or hard landings or anything out of the ordinary.  Would the gear then not extend because the up limit had not been reached?  I was under the impression it would still extend if the gear did not go up all the way.  The flybys I did with the gear retracted confirmed that the gear was indeed all the way up or very close to all the way.  During the emergency extension, I noted that I did overcrank it....I kept cranking after the green light came on.  After landing I stowed the emergency crank.  It looks like I did this properly.  One of the mechanics said it was safe to fly with the gear down, and that I could try to retract the gear.  I did and nothing happened.  In hindsight, that probably wasn't the best idea.

Could the bowed tube create all this?  Could I have bent the tube by overcranking the emergency extension?  

[KSMooniac]

It's easy to bend those tubes if the gear is impeded during motion. A quick overload causes them to buckle. I'm not sure if over cranking by hand would do it, but it would not surprise me. I would not fly it or even taxi it in that condition as you're risking a gear collapse if you over come the preload with a bump or side load.

You should replace it, or straighten it and do a welded splice repair over the top in accordance with 43.13.

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[N201JG]

Thanks for the input on the tube.  It's in the shop now so it's not moving until we get this figured out.  I'm starting to think something blocked it on the way up.  Could a rat sock do that if it was hanging in the gear path?  Mine need replacement and I was messing with them just prior to this flight so I could look into options for replacement.

[larrynimmo]

FYI….during annual, I had my AI remove my gear box so I could send it out for the spring replacement….after Re-installation, we had tested manual operation….problem is my AI left old tires under landing gear as a jack while gear box was removed.

we had exercised the manual extension and we bowed and bent a rod.  While we did remove and straightened the rod, my AI said I need a new rod….$650…

that was 3 years ago…not so painful anymore

[carusoam]

Landing gear rods are known to be sensitive to improper rigging…

It doesn’t take much force to bend or break them…

Broken rods have been known to cause a gear collapse…

 

I haven’t heard of mis-using the manual extension causing an issue…

The gear are either down, or not down…

We have two indicators for that…. The light is nice… the window on the floor let’s you see the gear in position or not….

 

Rigging the gear… Find somebody that has done this before…. It is too easy to not recognize something incorrect…

Adding other variable into the mix… like unbending a rod, or welding one….   
 

The objective of this conversation is to end up with less questions than you started with….

 

Welding a control rod for a seat is one thing… adding a variable to how the gear system works….  That would cause me to lose sleep every night before a flight…

See if you can find examples of where people have repaired any of the gear rods…. There has got to be some example around here somewhere…

There was a long body that had a gear up caused by mis rigging and a broken rod….  I don’t recall how it got fixed…

Best regards,

-a-