Flap Pump Questions

[Sven]

The bane of my existence is the Mooney flap pump. There's always an issue. It's either leaking, not pumping at all, or it's leaking (did I already say that?). For the third time in four years I've installed a new kit from LASAR. Only this time the kit had an interesting option. On the large piston instead of two leather spacing washers there were two rubber washers. I decided to go with the rubber instead of the leather. Magically, there's no leak out the air hole. And, the pump handle is now spring loaded and returns to the down position when not under pressure.

 

My questions: Is this normal? Is the handle spring-loaded favoring the down position? Because of the tightness of the leather washers I've never experienced the spring-loaded feature. Maybe there's more like me out there who've never experienced a spring-loaded flap pump lever. And did I mention it no longer leaks?

[Bob_Belville]

The lever in my '66Es does not move unless I move it. Interesting. (I've seldom had any problems at all from the flap system except for the Mickey Mouse indicator linkage.)

[rbridges]

I thought the manual pumps were supposed to be relatively bullet proof.  I've never had any issues with mine, and my handle is not "spring loaded."  It pretty much stays where it's left.

[orionflt]

As far as I know my flap system hasn't been touched since it was installed in dec of 61 and the only seepage I get is from the actuator...if you want to call a couple of drops that I wipe off during the annual seepage. Also mine is not spring loaded at all it will stay in what ever position you leave it.

[N601RX]

It seems it would have to be leaking fluid by the piston to automatically return to the down position.  That doesn't sound correct.

[Bob_Belville]

Sven, what model/year is it we're talking about? 

[Shadrach]

The Manual flap system is a simple and elegant device that can be a challenge to set up if you're not entirely sure what you're doing. The trouble is that many A&Ps and owners aren't entirely sure what they're doing.

To address your "spring loaded" issue. I suspect that the pump is returning to to the "handle down" position because fluid is not flowing into the pump cylinder. When you draw up on the pump the piston goes to bottom dead center. If fluid or air is unable to enter the cylinder, you will get a vacuum in the cylinder which will cause the flap handle to return to it's original position sans effort from the operator. This is likely due to a problem with the adjustable check valve and or an indication of significant air in the system. If in fact you were drawing fluid into the pump cylinder, there is nothing to push the fluid back out. If you create a void that is not filled with fluid or air, then you'll have a vacuum. This will cause the symptom you've described.

The first thing I would do is loosen the check valve bleed screw and back the adjustment all the way out, then tighten the collar so it does not leak.

IF LOOSENING THE BLEED SCREW DOES NOT SOLVE YOUR "SPRING LOADED" ISSUE THEN THE PUMP MAY HAVE BEEN REASSEMBLED INCORRECTLY.

The next thing is to ensure the system is properly bled (this is where most fail). IIRC the MM calls for it to be bled like you would brakes...from the top. I am of the opinion that it is far more effective to bleed it from bottom to top starting at the actuator.

My "12 step" program is as follows and is based on starting with the flap system drained of fluid:

1) Loosen the bleed screw (as I've already stated above).

2) Ensure that the small lever in the "flaps up" position (this is to say needle valve off the cam lobe that opens the check valve).

3) Remove the plastic blocking plate from the T shaped AN fitting on the ACTUATOR (lowest point in the system) and attach a pressure pot filled with the specified hydraulic fluid.

4) Attach an AN fitting with a 2' hose to the reservoir to act as an overflow. position the hose over a catch can (bucket).

5) Actuate the pressure pot and watch for fluid at the overflow hose at the front of the aircraft.

6) When you detect fluid coming through the overflow, cut the pressure from the the pressure pot.

7) Plug overflow hose and reservoir vent.

8) This is where it gets messy... remove pressure pot fitting and replace the blocking plate.

9) Remove whatever you used to block the reservoir vent plug (I've used chewing gum). Leave the overflow plug in place.

10) Select "down" position on flap lever and have someone simultaneously pump the the handle (slowly) while you back off the plastic plate on the aforementioned actuator "T fitting" just enough to allow it to leak. You should get fluid only, but possibly a small amount of air and then fluid. Have your pump person maintain gentle pressure. Make sure to only have the bottom of the system open under positive pressure from the pump person. Close it under pressure. If the person pulls up on the flap pump and the system is open it will draw air into the system...

11) With T fitting secure, pump the flaps down. Remove overflow hose, retract flaps and be ready with a rag to catch any overflow. If fluid level is too high in the reservoir , siphon a bit off with a drinking straw (use your thumb not your mouth).

12) close up the system, adjust flap retraction speed set screw so that the flaps take apprx 10 secs to retract, ops check, button everything up and go fly...

Edited November 16, 2020 by Shadrach

[Shadrach]

It seems it would have to be leaking fluid by the piston to automatically return to the down position.  That doesn't sound correct.

Negative...He is describing a piston vacuum lock...

[N201MKTurbo]

If you stretch the spring on the inlet check valve, it'll do that. The area of the ball seat is about 1/100 th of an inch, and atmospheric pressure is about 15 psi, if the spring pressure is above 0.15 lbs it will not be able to unseat the ball.

[Sven]

Thanks for all the wisdom and the replies. I've ordered a pressure pot which Amazon will deliver tomorrow per Shadrach's suggestion. I'll let you know how it turns out.

 

I'm the guy with the unconverted D model.

[mikerocosm]

Not really wishing to hijack this thread, but it seems pretty satisfactorily completed, so . . . Let me ask Shadrach where I might find that flap retraction speed set screw? My flaps retract in about a second flat, and it would be great to slow them down to a speed I might actually be able to control.

 

Thanks, Mike

[BigTex]

Mike, If you look at your maintenance manual, page 6-15, figure 6-11, you'll see a picture of the flap pump and valve assembly (assembly no. HE-626. On that picture, you'll see the screw that you'll have to adjust. The drawing state "turn the screw clockwise to slow the rate of the bleed off of fluid 8-12 seconds." Unless you have Don's Hangar elf, you'll likely have to have your mechanic adjust it. Let me know if you need this drawing.

[Shadrach]

This is definately not a procedure approved under 14 CFR Part 43. I share procedures that I have worked through under the supervision of my IA. All MX procedure described by yours truly in this thread and elsewhere should be completed in compliance with US FARs. Whew... now that that's out of the way.

Any A&P or owner under supervision of an A&P should be able to complete this task in under 2 hours; less if you have a one piece belly. See screw in attached illustration; it is called a restrictor. I have annotated both attachements (crudely) to point out the part in question. The "restrictor" controls the speed of the outflow back to the reservoir. Turning the restrictor clockwise will reduce the flow and in turn reduce the rate at which the flaps return to the "up" position. Turning the restrictor counter clockwise will have the oposite effect. It is a good idea to snug the restrictor nut down for each adjustment to prevent leakage. It wil likely take several tries to get it where you want it, which is between 6 and 10 secs for the flaps to return from full down to the up position; this translates to an airborne retraction time of between 2 and 6 sec.

Flap Pump close up.pdf

Brake and Flap Sys.pdf

[kellym]

 

Any A&P or owner under supervision of an A&P should be able to complete this task in under 2 hours; less if you have a one piece belly.  See screw in attached illustration; it is called a restrictor. I have annotated bot attachement (crudely) to point out the part in question.  The "restrictor" controls the speed of the outflow back to the reservoir. Turning the restrictor clockwise will reduce the flow and in turn reduce the rate at which the flaps return to the "up" position. Turning the restrictor counter clockwise will have the oposite effect. It is a good idea to snug the restrictor nut down for each adjustment to prevent leakage.  It wil likely take several tries to get it where you want it, which is between 6 and 10 secs for the flaps to return from full down to the up position; this translates to an airborne retraction time of between 2 and 6 sec.

Let me point out that this is a VERY touchy adjustment. Less than 1/8 turn from very fast to slow flap retraction. Patience and very small adjustment is key.

Kelly

A&P/IA

[Shadrach]

Agreed Kelly, it seems like even less than that on mine. It's also a PIA to hold the restrictor in position while tightening the nut that holds it in position. I've learned that it need not be "armstronged", nice and snug is all that's needed...

[Shadrach]

David, the schematic I posted shows the location (it's the big belly panel between the wings), I suggest you find a friendly A&P to assist you in the process... 

[carusoam]

How do you set the timing on the ground, with no additional wind pressure? (I don't recall)

Something you can think about before taking the panel off a third time...

Best regards,

-a-

[Shadrach]

How do you set the timing on the ground, with no additional wind pressure? (I don't recall)

Something you can think about before taking the panel off a third time...

Best regards,

-a-

 

 

12) close up the system, adjust flap retraction speed set screw so that the flaps take apprx 10 secs to retract, ops check, button everything up and go fly...

 

 

 

From post  #7 IIRC the MM cals for 6 to 10 seconds on the ground. I'd bet you ten to one that they put that range in there to keep people from going nuts trying to get to an exact number. It's very sensitive. 6-10 on the ground seems to translate to about 3-5 sec at flap speed...

[Shadrach]

He's clearly up on the latest aviation maintenance trends! He must get the PAMA newsletter. Better make it Quakerestate, and don't forget the gauze pads... ;-)

[Shadrach]

The Fetzer valve or the flaps?  Are they working to your satisfaction now? Any issues? 

[Shadrach]

Sven, don't leave me hanging... how'd you make out?

[Sven]

The backfilling procedure worked flawlessly. I've attached a few photos that will hopefully illustrate things for wishing to follow. It's important to use hose clamps. Once you pressurize the pot, which I did to almost 20 lbs, anything that can leak will leak. Save yourself some cat litter absorbent and use the hose clamps where you can. I'm not sure what order these will appear so I'll comment on them alphabetically.

 

On the actuator attachment you first need to slightly pressurize the pot ridding the line of air. As the fluid reaches the end of the hose slide it on the actuator fitting with your hose clamp ready to seal it off. 

 

I made fluid catch jars from clean new Mason jars with holes cut in the lids. They both actually had lids but this photo shows one of the lids off. I used two and you'll see why in the Reservoir Tubing photo.

 

The Fittings photo show how I connected the hardware that came with the pressure pot to the line that connected to the actuator. THe pressure Pot line wasn't really long so I needed to add a length of tubing. This is how I did it.

 

Pressure Pot: I got this on Amazon right here and it even arrived on a Saturday with Amazon Prime. I paid $58 but it was well worth the price in time saved and mess not created. I even used the same method to backfill my brakes. It worked amazingly well.

 

Reservoir Tubing: I went for safety since we just installed a new interior. I put hoses on both places fluid can exit the reservoir. I'm very glad I did as it came out both places. Sorry I didn't take a picture of the entire fittings contraption I rigged. I packed it with old rags to prevent any leakage from hitting the new carpet.

 

I bled the system without assistance. I did have to jiggle the small actuator arm on the flap pump itself (not the actuator that connects to the flap). This is the small arm that "dumps" the flaps. Mine didn't want to behave in the open position. By moving it back and forth the fluid moved through the system and out the reservoir tubes. 

 

A huge thanks to Shadrach for this amazing procedure that saved me time, frustration and a giant mess. 

[Shadrach]

Holy cow! The hardware you used is almost identical to minel...right down to the grey Chuck Taylor's!

[captainglen]

The springiness to the pump is not normal as I am sure you noticed while rebuilding the pump there is no spring. The pumping is done by the shaft side of the piston so extending the rod moves fluid to the flap actuator. The far side of the piston breathes air through the weep hole; if the piston seal is bad 5606 will be vented through the weep hole. The only think of that could cause a spring action is if the weep hole were clogged allowing air pressure to build behind the piston. While I am at it though and since you have been through this a few times; is there any trick to bleeding the flaps.

 

[N201MKTurbo]

If the inlet check valve is not working, a vacuum will be formed in the pump chamber when the handle is raised. The vacuum will pull the handle back down when released.