Bent Push Pull Rods

[BlueDun]

Had occasional nose shimmy. Appeared fixed after 2020 annual. Shimmy came back and fixed at 2021 annual (with new shop). At 2022 annual, gear made an odd noise when plane lifted and actuated. 

Got a second opinion with an MSC: push pull rods are bent and the spring tension is beyond limits. Can send pics. As you know, things are intricately connected, so likely more to discover/fix. The shop has seen this issue only once before, which was another long-body Mooney (a '98 O?). That led to a left gear collapse, damaging the wing and tail. That was my likely fate, which was thankfully avoided.

Have we bounced before? Sure, a couple of mild ones. Teeth rattling landings or any skidding? No. Had a flat tire once in 2019. Otherwise, no issues. No over-weight landings. I fly final at 80kts, and often lower when light. Routinely land softly and short. I would think a shop would see bent rods more often if this were a landing issue. I know of no prior damage.

I heard a motor actuate once before when turning on batt. That was odd. It occurred after the annual that discovered the gear noise, however. If it was the gear motor at some point, which should be inspected at 1,000 hours, could the jack screw bend the rods while the plane is on ground?

Has anyone else, especially you MX folks, seen bent push pull rods and a cause? Is it rare and could it be a manufacturing defect?

Commentary, thoughts,  or experience welcome... She'll be down for a while.

====

Other stuff. 2006 Ovation 3. G1000 WAAS, GFC 700, TKS. Purchased 2019. Thorough Pre-buy that turned into an Annual. We have been meticulous with mx, preventive care, and upgrades.

Made a number of repairs/upgrades on purchase, including latest G1000 update, ADSB in/out, fixed a minor hangar rash, serviced AmSafe belts. Happy with that work. MX since included TKS repair, new starter, baffles, GAMIjectors, landing height system. Cylinder #5 heat solved! All this may not be relevant.

Other gremlins: Recently, elec up trim stopped working after the G1000 booted, or was inconsistent, starting in 2021. Auto pilot was fine. Down trim was fine. After latest database update, trim started working again.

[N201MKTurbo]

Those tubes get bent because of improper maintenance, not hard landings.

[BlueDun]

Thank you. I appreciate the response. Please tell me more about improper maintenance, if able. Seems like a good learning opportunity for all of us around maintenance issues. No doubt this is going to be expensive.

[BlueDun]

TLDR version of my first note: My ovation 3 has bent push pull rods. Who has experienced this, has thoughts on this, or knows specific causes? Things to look out for as we fix etc. Look forward to learning a lot as my plane goes through this repair process.

[PT20J]

Each gear is held in the down position by an over-center mechanism that is spring loaded. For the nose gear, the coil springs are at the forward ends of the push-pull tubes. Spring tension is adjusted by screwing or unscrewing the forward rod ends. If adjusted too tight, the springs will bottom out before the gear is fully extended. The motor has a lot of torque and if the springs bottom out, something has to give.

Skip

[A64Pilot]

25 minutes ago, BlueDun said:

Thank you. I appreciate the response. Please tell me more about improper maintenance, if able. Seems like a good learning opportunity for all of us around maintenance issues. No doubt this is going to be expensive.

Being out of rig.

OR I think a defective limit switch could do it, and could be what happened that one time you turned the Master on and the gear motor ran, that’s not normal.

I’d inspect the down limit switch and it’s stop “paddle” if you find a bent paddle You may have found a smoking gun.

That’s all supposition of course, but I think a hard landing unlikely to do it, and pretty much anything else I think of would only bend one gears tube.

[BlueDun]

6 minutes ago, A64Pilot said:

Being out of rig.

OR I think a defective limit switch could do it, and could be what happened that one time you turned the Master on and the gear motor ran, that’s not normal.

I’d inspect the down limit switch and it’s stop “paddle” if you find a bent paddle You may have found a smoking gun.

That’s all supposition of course, but I think a hard landing unlikely to do it, and pretty much anything else I think of would only bend one gears tube.

Thanks for these tips! Appreciate the fast response. I look forward to keeping you posted here as well.

[A64Pilot]

That motor, mine anyway is rated to apply 2,000 lbs of force.

In our application it doesn’t use anywhere near that much force and I think in our application the CB would pop prior to applying that much force, but it can easily bend landing gear actuating tubes.

 

[BlueDun]

1 minute ago, A64Pilot said:

That motor, mine anyway is rated to apply 2,000 lbs of force.

In our application it doesn’t use anywhere near that much force and I think in our application the CB would pop prior to applying that much force, but it can easily bend landing gear actuating tubes.

 

Woah!

[BlueDun]

Here are some photos. Always interesting insight/commentary here on such things. Go, Mooneyspace.

 

[EricJ]

50 minutes ago, BlueDun said:

TLDR version of my first note: My ovation 3 has bent push pull rods. Who has experienced this, has thoughts on this, or knows specific causes? Things to look out for as we fix etc. Look forward to learning a lot as my plane goes through this repair process.

The SMM for the J model says there's a bend allowance of 0.010" per foot, but I don't know if there's a difference for an R model.   That looks like it's likely past that, though.

[BlueDun]

29 minutes ago, EricJ said:

The SMM for the J model says there's a bend allowance of 0.010" per foot, but I don't know if there's a difference for an R model.   That looks like it's likely past that, though.

Well past

[Guest]

The nose gear rods are stretched during gear extension, while the the main rods, the bent ones in the pictures above are compressed during gear extension.  Gear mis adjustment, a failed/ failing down limit switch may be causes.

[PT20J]

53 minutes ago, M20Doc said:

The nose gear rods are stretched during gear extension, while the the main rods, the bent ones in the pictures above are compressed during gear extension.  Gear mis adjustment, a failed/ failing down limit switch may be causes.

Thanks, Clarence. I looked at it again and I clearly got it backwards.

[BlueDun]

17 hours ago, M20Doc said:

The nose gear rods are stretched during gear extension, while the the main rods, the bent ones in the pictures above are compressed during gear extension.  Gear mis adjustment, a failed/ failing down limit switch may be causes.

Thank you, Clarence. I'll keep you apprised.

[RLCarter]

23 hours ago, A64Pilot said:

That motor, mine anyway is rated to apply 2,000 lbs of force.

In our application it doesn’t use anywhere near that much force and I think in our application the CB would pop prior to applying that much force, but it can easily bend landing gear actuating tubes.

 

My gear (J-bar) was grossly out of rig when I purchased it, best guess was it took 60lbs + of force to get the gear in the down (bar up) position, in my pea brain that was 1200lbs on the other end if the J-bar is 20” long. Granted once it was cleaned, repaired, greased and rigged correctly it was 1/10 the effort

[A64Pilot]

35 minutes ago, RLCarter said:

My gear (J-bar) was grossly out of rig when I purchased it, best guess was it took 60lbs + of force to get the gear in the down (bar up) position, in my pea brain that was 1200lbs on the other end if the J-bar is 20” long. Granted once it was cleaned, repaired, greased and rigged correctly it was 1/10 the effort

I’ve been thinking about that, I don’t think the J bar has any mechanical advantage, which means the gear mechanism shouldn’t be under high stress in normal use.

The J bar has about the same arc sweep as the gear, about 90 degrees, and has about the same length as the main gear, so how could it have any?

I’ve not measured any of this, just going off of memory from almost 50 years ago.

60 lbs and an arm of 20” gives 1200 in lbs of force or 100 ft lbs, but that’s at the center of rotation of its fixed point, force drop off the further from the center of rotation.

[N201MKTurbo]

53 minutes ago, A64Pilot said:

I’ve been thinking about that, I don’t think the J bar has any mechanical advantage, which means the gear mechanism shouldn’t be under high stress in normal use.

The J bar has about the same arc sweep as the gear, about 90 degrees, and has about the same length as the main gear, so how could it have any?

I’ve not measured any of this, just going off of memory from almost 50 years ago.

60 lbs and an arm of 20” gives 1200 in lbs of force or 100 ft lbs, but that’s at the center of rotation of its fixed point, force drop off the further from the center of rotation.

The bell crank at the bottom of the J bar has a radius of about 2". That gives you about a 10/1 force advantage, so 60 Lbs. on the J bar gives ~600 Lbs. at the push rods.

A properly rigged J bar takes very little force to seat it in the socket. 

When I picked up @ragedracer1977s Mooney when he first bought it, I told him the J bas was out of rig and it took too much force to lock it down. About two years later, He asked me to fix it. After getting everything adjusted properly, The wheels went down with little effort. 

[A64Pilot]

At the tubes yes, if it’s 2”.

At the wheels, no, the system has little if any mechanical advantage.

A testament if you will how little force is required to cycle the gear.

The electric though has a mechanical disadvantage, meaning that the linear actuators movement is less that the wheels movement. I’ve not measured it’s travel though it’s just an impression, but if has the capability of 2000 lbs of force, I doubt it’s using 10% of its rated capacity.

[N201MKTurbo]

The main gear (and through the rods, the nose gear) is counterbalanced by big springs. If you remove the retraction rods, you can move them easily from all the way up to down and locked.

[Yetti]

It looks like your gear has been improperly worked on.   The hole next to the motor looks like it was enlarged and then the edges smoothed.   See the missing primer.   The hole is how you get to a bolt to get the motor out.   My grumpy IA had a ground down long socket that would fit the factory hole.

Bending of the tubes is probably due to miss rigging the gear.   Best to not mess with the gear unless you need to.   Most gear problems can be fixed by doing a good lube.

I find the Mooney gear to be fascinating in design and ability to work and pack all the tubes into the wings and such.

 

[BlueDun]

@Yetti I find it fascinating as well. Thanks for spotting that. I am not aware of any gear work since my 2019 purchase but we will go back through logs. Tried to orient myself to the pic to see what you do, but am having trouble. Would you mind highlighting the pic so I can see it as you do?

[Yetti]

39 minutes ago, BlueDun said:

@Yetti I find it fascinating as well. Thanks for spotting that. I am not aware of any gear work since my 2019 purchase but we will go back through logs. Tried to orient myself to the pic to see what you do, but am having trouble. Would you mind highlighting the pic so I can see it as you do?

First pic with the straight edge.  See the 1" shiny spot around the hole to the right?   Then on the bottom of the shiny spot you can see where they used a rotory scrubber wheel.   See the half swirl marks.   It might be different in the later models, but in my 75' F that hole is used to get to the bolt that holds the end of the actuator.   It's a 7/16" socket I think.   The IA had a perfectly ground down socket to fit the smaller than yours hole.   I think Snap on makes some thin wall sockets that would also fit.    

You could probably look that part number up in the Parts manual under the empanage section.    For the most part I would think the actuator had been lubed and serviced at some point.   Also you might want to order the CD for your plane from the FAA.    There were a couple of things about my plane that were not in the logs.

 

[BlueDun]

41 minutes ago, Yetti said:

First pic with the straight edge.  See the 1" shiny spot around the hole to the right?   Then on the bottom of the shiny spot you can see where they used a rotory scrubber wheel.   See the half swirl marks.   It might be different in the later models, but in my 75' F that hole is used to get to the bolt that holds the end of the actuator.   It's a 7/16" socket I think.   The IA had a perfectly ground down socket to fit the smaller than yours hole.   I think Snap on makes some thin wall sockets that would also fit.    

You could probably look that part number up in the Parts manual under the empanage section.    For the most part I would think the actuator had been lubed and serviced at some point.   Also you might want to order the CD for your plane from the FAA.    There were a couple of things about my plane that were not in the logs.

 

I think I see what you mean, but the hole looks the same size to me as the others. Of course, I have newbie eyes.  I will pass this along to the shop. Thank you.

What is the CD for the plane from the FAA you mention?

Anyway, all this help reminded me to make a Mooneyspace donation to support this great site. 

[N201MKTurbo]

On 12/15/2022 at 3:47 PM, M20Doc said:

The nose gear rods are stretched during gear extension, while the the main rods, the bent ones in the pictures above are compressed during gear extension.  Gear mis adjustment, a failed/ failing down limit switch may be causes.

If it was rigged properly, wouldn’t it buckle both tubes?