Flaps not in sync

[XXX]

Hello,

Has anyone experienced flaps out of sync or a "lazy" flap? My right flap does not travel in sync with the left while in flight (it lags behind). On the ground both are in sync. Any thoughts would be appreciated.

 

Thank you,

 

Steve

[carusoam]

Welcome aboard, Steve.

Stand by for a response from our guys with flap experience.  They'll be along soon...

In the meantime see if you can describe what happens to make your flaps misbehave.

Is one not retracting all the way?  Do they both go down all the way?  Is there a roll tendency associated with the uneven deployment? (Either when up or when down?)

There are some stops that may be adjustable.  Beyond that, I'm not familiar...  I am only a PP not a mechanic.

Best regards,

-a-

[XXX]

Thank you Carusoam,

Yes, I should elaborate. Flaps retract normally after take off. It is when putting in landing flaps that the right one lags behind. It seems like air pressure is holding the flap up. When enough airspeed bleeds off (generally in the landing flair) the flap will continue down to the full flap position.

[carusoam]

Steve,

Since the flap system is hydraulic pressure based, there shouldn't be much room for changing position based on air pressure being relieved from the flaps...

Can you describe the number of pumps you give the flaps to their relative position?  You might be seeing issues caused by air in the lines between the pump and flap actuator.

I'm still not a mechanic, I used to have an M20C with the hydraulic flap system...

I would get something like this... (Illustration of my point)

# of Pumps  -    Observation

  1 - pressures the system, but no motion.

  2 - 10°

  3 - 20°

  4 - 30°

  4.3 - 33°  Both flaps all the way down to their stops...pump handle doesn't go any further.

In a decade of ownership, my flaps never changed adjustment.  Seals and hoses got changed completely.

On a similar topic... Somebody recently posted a picture of the pair of flap retraction assist springs.

Best regards,

-a-

[XXX]

My flaps are electric and driven by push rods. The motor is on the left side so there is more distance and possibility of wear in the linkages to the right side. I'm guessing this is the cause but was hoping someone else may have experience with the same issue.

[carusoam]

There has been much discussion of F flaps (and others) and their limit switches.  Including some really detailed photos.  Should be easy to search for.  Search box is at the top right side of the page...

I just don't remember a split flap deployment.  That could make for a memorable flight...  Sounds like something has come loose in the flap system. While on the ground can you sense one flap being loose?

Are you heading to the mechanic with what you have found?

Best regards,

-a-

[XXX]

Carosoam,

I appreciate you helping me to get up to speed on the board. I will certainly work on being more specific with future inquiries.

On the ground with full flaps I am able to lift the right flap about 1 inch while the left only moves about 1/4 inch. I am scheduled to see the mechanic next week and will provide updates. In the meantime, I sure would be interested in hearing from anyone who has experienced out of sync flap deployment.

Thanks,

 

 

[carusoam]

All the lucky Mooney pilots must be out flying today...

Following the logic...

There is one drive motor, both flaps are linked to it. There are adjustable links along the way inbetween.  Adjustable by disconnecting and rotating them.  

Having one flap moving independently, sounds like one of the links may no longer be attached properly.(?)

The nice thing is you can legally remove a couple of inspection panels if you know exactly which ones they are.  Keep in mind opening inspection panels without knowing what's behind them can open the bottom of a fuel tank.  Best to wait for your mechanic in that case.

hopefully, you will get some additional guidance here...

Best regards,

-a-

[Guest]

Generally the flaps on a Mooney work the same whether they are hydraulic or electric.  There is a torque tube supported by 4 bearings on the rear false spar.  The area is accessed thru the last large belly panel held on with 10-32 screws.  The outer ends of the flap torque tube connect to the flaps thru a pair of rod end bearings, one male and one female. . Loss of travel could be loose bolts on these rod ends, worn rod ends or a damaged torque tube.

It should be easy to figure out once the cover is opened.

Clarence

Edited April 2, 2016 by M20Doc

[Piloto]

The inboard rod end may be broken or loose. With the flaps in the takeoff position grab each flap and check for play or backlash. 

José

[Andy95W]

There are two flap adjustments.  

-The outboard stops at the ailerons which adjust flap angle at the fully retracted position.

-The inboard linkages which are accessible through the aft- most belly panel.  Adjusting these will affect the rate at which the torque tube starts moving the flaps themselves.

I sounds like your issue is probably the inboard adjustments.

[XXX]

Clarence, Jose and 95W,

Thanks guys. It's looking like the linkage could be the issue. I'll post my findings. I appreciate all the input.

[XXX]

Update...

Here are some pics of the linkages and torque tube. The hole for the right arm drive was wallowed out and had quite a bit of play, so my mechanic drilled it and installed a bushing (pic 2, bushing hidden by washer). It has helped a bit with the right flap moving, but It still lags behind the left flap and doesn't fully extend until the airspeed bleeds off to practically touch-down speed.. The next step will be to address the other linkage points.

It seems odd that no one else has experienced this.

Edited April 9, 2016 by Chupacabra
clarification

[Andy95W]

While you're there, my suggestion is to check both of those inboard pushrods to see if they are the exact same length.

[carusoam]

From a PP point of view...

the adjustment on the rod end is fully closed up.  Making it not much of an adjustment.  I would have expected to see a few threads if it were adjusted properly.  Could be something else amiss causing somebody to close that up...

Best regards,

-a-

[XXX]

OK, I wanted to update the findings here just in case anyone else has this issue in the future. Through a series of procedures, my mechanic found the Flap jack tube (torque tube) is "twisting" when it has pressure on it from the right side. Everything works as it should on the ground, but when airborne the air pressure holds up the right flap causing uneven deployment.  We think the tube might be corroding from the inside and is weakening. I found a serviceable used unit that will go in next week and will post the results.

Also, it's hard to believe no one else has experienced this since it's the same part number from the "F" through the early "K" models. Possibly because no one is watching their flaps while they deploy them?

[ryoder]

Does it cause the plane to roll?

[Yetti]

I would guess that someone stepped on the right flap at some point and that bent or weaken something.  Then over the years since things were not aligned the holes got wallered out.

[Piloto]

A broken or loose flap rod during take off or landing can cause a hard roll. During preflight inspection check flaps for play. If an unexpected roll is experienced raise the flaps immediately. A fully deflected single flap can overpower an aileron deflection.  

José

[XXX]

14 hours ago, ryoder said:

Does it cause the plane to roll?

Yes, It rolls slightly to the left when I deploy them but immediately goes back to level. I've landed with them several times  this way. The right catches up once the speed bleeds off on the ground.

[Yetti]

Sounds like your PC system is working and leveling the plane after the asymmetrical flap deployment

[captainglen]

Do Not mess around get it to a mechanic ASAP. Something is bent loose or broken such as a weldment. If you were to experience an inflight failure with the flaps down there would be a large flap disagree with a tremendous rolling moment. You could recover if you retracted the extended flap if there is enough altitude which is unlikely on short final.

[XXX]

13 hours ago, captainglen said:

Do Not mess around get it to a mechanic ASAP. Something is bent loose or broken such as a weldment. If you were to experience an inflight failure with the flaps down there would be a large flap disagree with a tremendous rolling moment. You could recover if you retracted the extended flap if there is enough altitude which is unlikely on short final.

Captainglen,

Thank you for the input. I just got it back from the mechanic and it is working well. Here is what he found. The torque tube that the jack screw drives would twist slightly when pressure was held under the right flap simulating air pressure. Also, out of the four mounting holes, at least two were wallowed out allowing some play. Finally there were two loose rivets at the bracket that attaches to the flap and the short control rod. After installing a serviceable torque tube and repairing the loose rivets, it works.

Yetti's theory of the right flap being stepped on by a heavy person at some point seems very plausible. In fact I just ordered a "no step" placard for the flap.

The motor and jack screw are located closer to the left side of the torque tube. The difference in span to the right is about double so that makes for a worn out system to manifest itself in an uneven flap deployment.

Steve

[Hank]

Thanks for the update, Steve. And double Thanks for doing this the right way. We'd all rather read your writing than read about you . . .

[mike_elliott]

1 hour ago, Chupacabra said:

Yetti's theory of the right flap being stepped on by a heavy person at some point seems very plausible. In fact I just ordered a "no step" placard for the flap.

I adopted a policy to put the flaps in TO position and trim in TO position on shutdown. Originally, it was so it would be easier for my dog to jump up on the wing and get in, but I found it also discourages people from stepping on the flap. If I or anyone were to forget to set things correctly on TO, they already are. Mooney flaps are tough, but not Maurader chick tough. With manual flaps there might be the downside of having hydraulic pressure left on, but I cannot see that being a big deal as it isn't much pressure and shouldn't be on for years. I will also verify flap ops and elect trim in both direction prior to launch.