Maintenance HELP - flaps!

[nishantc04]

I have a 1965 Mooney M20C (serial number 2812) going through an owner assisted annual inspection right now.  Unfortunately we’ve hit a kink in the process and I need help.

HISTORY – Before the annual inspection, I would use partial flaps on take off and full flaps on landing regularly.  The plane was flying about 4 hours per week for the past 3 months (when I bought the plane).  There were no discernable issues with the flap system.  The sole discrepancy is that the flaps took about 2 dead pumps before the flaps began moving.  In addition, there was an unknown hydraulic fluid leak on the belly of the aircraft (only noticeable if the belly pans were removed). 

THE ANNUAL - The A&P I am working with knows Mooneys well and works on them regularly. 

1.    The unknown hydraulic fluid leak was traced to the manual flap cylinder pump.  The manual flap pump was leaking hydraulic fluid and was overhauled.  The o-rings in the flap cylinder pump were simply replaced and the leak stopped.  

2.    The flap system was bled at both the flap pump and the actuator.  The system was still taking about 2-3 dead pumps before the flaps would begin moving.  My A&P pressure bled the system and now the flaps begin moving at the first pump.  

THE PROBLEM:  It takes about 5 pumps to get the flaps all the way down (as expected).  The system holds full flaps with no problem.  However, at partial flaps (such as the take off setting) the flaps begin retracting automatically.  AHH!

POTENTIAL CAUSES: I have no idea what happened!  My thoughts are that the pressure bleeding has roots in the problem.  After the o-rings were replaced and the flap pump was reinstalled, when we were bleeding the system I recall stopping at partial flaps – the system would hold it.  After the pressure bleeding, though, the system would not hold partial flaps. 

 

Unfortunately I wasn’t there for the pressure bleeding process.  My A&P says that he’s done everything he can do to the flap control and it still doesn’t work.  He specifically mentioned, “I disconnected the wire that activates or retracts the flap at the control valve and spun the control valve 360 degrees and did not get any results.”

 

If anybody has any knowledge or ideas here, please help me!!

 

Thank You,

 

Nishant

 

[triple8s]

Ok if you push the small lever to make the flaps stay down (hydraulic valve lever)  and pump the flap lever to deploy the flaps, do they go down a bit then come back up as you bring the pump handle up for another stroke? I would think it would have to be a problem with the valve that is conected via the cable to the small lever. I'd definetely replace the O-rings in the valve as well. Check the valve, the valve diverts oil thru a one-way check when closed and it sounds like there could be debris (piece of old o-ring) keeping the check ball off the seat a bit.

[triple8s]

I'm going to get the service manual for mine it is S/N 2895 M20C and I'll make sure. Be back in a few minutes.

[triple8s]

Hydraulic Flap System Bleeding  (from service & maintenance manual # 104)

When flap action becomes erraticor when repairs requirethe replacement of actuating components, it is necessary to bleed the Hyd flap system. Best results are acheived with the use of clean hydraulic fluid from a hydraulic fluid system bleeder (pressure pot) pressurized with air to approximately 35-40 psi.

1. 
   
2. Remove hydraulic reservoir vent cap.
   
3. Disconnect hydraulic cylinder piston rod from jack shaft.
   
4. Open bleed valve in "T"-fitting at hydraulic cylinder.
   
5. Pump actuating handle and observe flow of fluid from bleeder valve into catch pan.
   
6. When fluid clears of bubbles and runs transparent, slide shaft and piston to bottom to expell air
   
7. Pump actuating handle to re-extend piston and shaft.
   
8. Repeat steps 5 & 6 until all traces of air is removed from expelled fluid.
   
9. Close bleed valve
   
10. Remove exess fluid from reservoir through side plug to re-establish proper level.
    

The above is taken from my service & maintenance manual if the mechanic did get all the air out of the system it has to be debris under the ball valve. There are 2 ball valves, one is between the valve and cylinder and another is under the bleed off adjustment, both have springs so if you arent careful the will go flyin when you take them apart. Good luck.

[nishantc04]

Problem solved! One of the springs that pushes the ball bearing in place was broken. Yay for a simple fix!!

 

Thank you for the help - much appreciated.

 

Nishant

[zerobearing2]

I'm about to start annual on my 68C, been having issues with extending the flaps lately. It takes about 2-4 pumps to "energize" the pressure in the handle before they start extending. On rollout, raising the flaps takes several minutes (this seems excessive time to me). The brakes work fine, and reservoir at proper level. Was thinking it might be time to overhaul the hydraulic flap actuator (basically just o-rings right?). Anyone know if there are part#'s for a seal kit?

[scottfromiowa]

Dana at Willmer MSC in Minnesota has a "flap handle" gasket replacement pack that is reasonably priced.  All replacement gaskets for overhauling the flap pump.  Give him a call.  Good luck.  I also had leaky brakes and flaps.  All replaced.  Great to have solid brakes and flaps again

 

[Clarence]

Slow reacting flaps can be caused by old sticky hydraulic fluid.  Over time it will become very sticky even in a closed system.

Some aircraft types we maintain call for regular replacement of the fluid.

[zerobearing2]

Just in case anyone follows up on this thread looking for part#'s; I ordered from Lasar the pump and actuator seal kits:

KIT098-001
KIT093

 

[carusoam]

Simple advice while working with your mechanic...

There are a couple of spring loaded ball bearing check valves that you will find while changing O-ring seals. 

They can be challenging to hold together while putting them back in to the valve body.  a touch of grease will temporarily glue them together while you assemble, and then later dissolves in the hydraulic fluid.

Best regards,

-a-

[zerobearing2]

update -

we replaced the seals in the pump and actuator and rebled the system. Fluid was very thick and sticky just as Clarence suggested. We flushed the system with fresh fluid and now the flaps extend nice and easy. However, even after bleeding the system completely for what felt like forever, it still takes 1 pump to pressurize the system before the flaps start extending. Does this mean air still in system or is this considered normal? 4-5 full pumps fully extends the flaps after the initial "pressurize" pump. Any suggestions?

 

 

[Clarence]

You must still have some air in the system.  It should pump and extend the flaps on the first stroke of the pump and a bout 4 1/5 pumps to fully extend the flaps.

 

Clarence

[Shadrach]

My 67F takes precisely 4 full pumps from 0 to full. I OH'd the pump back in 06 and had problems with the ball valve leaking until I "reseated" it with a drift and a mallet... I'll never know why it need it. Anyway, mine is properly set up and 4 pumps to the stops, I can't imagine why yours would be different.

[sreid]

Quote: triple8s

Hydraulic Flap System Bleeding  (from service & maintenance manual # 104)

When flap action becomes erraticor when repairs requirethe replacement of actuating components, it is necessary to bleed the Hyd flap system. Best results are acheived with the use of clean hydraulic fluid from a hydraulic fluid system bleeder (pressure pot) pressurized with air to approximately 35-40 psi.

Remove hydraulic reservoir vent cap.

Disconnect hydraulic cylinder piston rod from jack shaft.

Open bleed valve in "T"-fitting at hydraulic cylinder.

Pump actuating handle and observe flow of fluid from bleeder valve into catch pan.

When fluid clears of bubbles and runs transparent, slide shaft and piston to bottom to expell air

Pump actuating handle to re-extend piston and shaft.

Repeat steps 5 & 6 until all traces of air is removed from expelled fluid.

Close bleed valve

Remove exess fluid from reservoir through side plug to re-establish proper level.

The above is taken from my service & maintenance manual if the mechanic did get all the air out of the system it has to be debris under the ball valve. There are 2 ball valves, one is between the valve and cylinder and another is under the bleed off adjustment, both have springs so if you arent careful the will go flyin when you take them apart. Good luck.

[Shadrach]

Quote: sreid

Do any of you guys actually have a 'bleed valve' at the T fitting?  My 67 F has a standard AN 929 cap, which is what the parts catalog specifies.  I'm getting ready to bleed the flaps after flushing the hydraulic system during the annual this year (fluid was getting old and did some brake work).  Wanted to make sure the best way to bleed the flaps is to use this procedure and bleed through the T fitting with the cap removed.  Is it a pretty straightforward procedure?

Thanks.

Steve

[sreid]

Well, I bled them over lunch.  I just manually bled them (didn't use the pressure pot) through the T fitting at the actuator cylinder.  Followed the procedure step by step and it worked perfectly.  The only part that isn't completely clear in the procedure is that you have to install the cap prior to step 6, so the actuator will fill with fluid and extend the piston.  Then remove the cap prior to sliding the piston/shaft back to the bottom to expell air.  I guess they thought that was too obvious!  Took three iterations of steps 5 & 6 to get all the air out of the actuator.

Steve

[Seth]

Quote: Shadrach

My 67F takes precisely 4 full pumps from 0 to full. I OH'd the pump back in 06 and had problems with the ball valve leaking until I "reseated" it with a drift and a mallet... I'll never know why it need it. Anyway, mine is properly set up and 4 pumps to the stops, I can't imagine why yours would be different.

[jetdriven]

If you land on a 7000 or greater runway right on speed and kill the engine it will stop on its own long before the end comes up. 

[carusoam]

You will lose flaps long before brakes.

 

You will lose full flaps, before losing all flaps.

 

A slow leak, this will make a difference.

 

The reservoir position for the brakes is lower than the flaps.

 

Best regards,

 

-a-

 

[captasap]

1964 M20C    When we extend the flaps airborne there is a slight split resulting in roll moment with the first pump.   On the second pump all returns to normal.  4 pumps to full flaps.   Scratching our heads, any ideas?

[carusoam]

Take a look at your system drawings. 

Based on 65C knowledge, I don't think that it is possible to have one flap operate without the other.  There is one actuator and one return spring. 

You are probably not the only one to get some roll out flap deployment. 

Best regards,

-a-