Flap handle spring back

[Steve65E-NC]

My flaps are working but have a problem.  The handle wants to spring up after each stroke.  Used to be a solid four strokes to full flaps with no handle spring back.   Now about eight with a lot of spring back with each stroke.    Handle wants to stay sprung up with any flap setting.  I replaced o-rings two years ago and flaps seemed fine until recently.  When I release the latch they come up as usual.  No sign of fluid leakage and flaps stay down once set. 

[carusoam]

That would be the internal leak...

Ross is the MS go to guy for describing what may have failed with the hydraulic flap pump and system...

See if @Shadrach is around...

Best regards,

-a-

[N201MKTurbo]

You need to bleed your flaps.

[Steve65E-NC]

10 hours ago, N201MKTurbo said:

You need to bleed your flaps.

I think you are correct.  Pulling the belly pan is a job and a pain so I thought I would get any input here first to see if I might need parts.  I read the Service Manual.  As near as I can tell they want me to put a 35psi pressure pot into the top of the reservoir.  Guess I can cobble something up for that, I think I have a hose fitting for up there.  Any ideas on whether the air pocket is at the pump cylinder or the at the jack cylinder.  If it is at the pump cylinder that may take a lot of fluid to move the air back to the T fitting on the jack cylinder. 

[N201MKTurbo]

The air must be in the pump cylinder for the handle to spring back. That doesn't mean that there isn't air in the flap cylinder.

[Steve65E-NC]

4 hours ago, N201MKTurbo said:

The air must be in the pump cylinder for the handle to spring back. That doesn't mean that there isn't air in the flap cylinder.

I agree.  How important is it to provide extra pressure at the reservoir before starting the bleed?

 

[N201MKTurbo]

1 hour ago, Steve65E-NC said:

I agree.  How important is it to provide extra pressure at the reservoir before starting the bleed?

 

I've never done it that way. I just pump the flaps down, then loosen the fitting between the pump and the cylinder and let the fluid out as the flaps come up, then tighten the fitting and do it again until there is no air. It is messy, but it works. Don't let the reservoir get low.

[Immelman]

10 hours ago, Steve65E-NC said:

I think you are correct.  Pulling the belly pan is a job and a pain so I thought I would get any input here first to see if I might need parts.  I read the Service Manual.  As near as I can tell they want me to put a 35psi pressure pot into the top of the reservoir.  Guess I can cobble something up for that, I think I have a hose fitting for up there.  Any ideas on whether the air pocket is at the pump cylinder or the at the jack cylinder.  If it is at the pump cylinder that may take a lot of fluid to move the air back to the T fitting on the jack cylinder. 

Ross is the expert....

But as far as bleeding, I had good success with a garden sprayer, plastic tubing, and pipe clamps bleeding from the slave cylinder to get the bubbles working uphill. A little overflow hose off the reservoir and pumped new fluid until no bubbles.

But where did the air come from? Something is leaking...

[Steve65E-NC]

1 hour ago, Immelman said:

Ross is the expert....

But as far as bleeding, I had good success with a garden sprayer, plastic tubing, and pipe clamps bleeding from the slave cylinder to get the bubbles working uphill. A little overflow hose off the reservoir and pumped new fluid until no bubbles.

But where did the air come from? Something is leaking...

 

1 hour ago, Immelman said:

Ross is the expert....

But as far as bleeding, I had good success with a garden sprayer, plastic tubing, and pipe clamps bleeding from the slave cylinder to get the bubbles working uphill. A little overflow hose off the reservoir and pumped new fluid until no bubbles.

But where did the air come from? Something is leaking...

I bled down and refilled  a brake recently and that probably introduced the air.  I hope.

 

[carusoam]

Getting air out of the brakes is tough...

Getting air out of the flaps is really easy...

Unfortunately, this is a wicked old memory...

When we resealed the flap pump, all of the fluid was removed... and replaced...

It took two people... one to pump and the other to move the flaps....

After a few cycles, the flaps were working pretty well... not as well as what Ross had with his though...

mine still had the extra pump in the beginning to ‘pressurize the system’...

PP thoughts only...

Best regards,

-a-

[Steve65E-NC]

Ok.  I have tried extensive pumping through.  Even rigged a pressure fluid supply to add pressure and fluid to top of reservoir.  Finally drained down the entire flap system and refilled from the top.  No luck.  When I am pumping flaps down, the handle springs back up to mid position.  I can tell that this return is putting fluid back up into reservoir.  Nothing I have tried changes this at all.  On a down stroke the flaps will go down and then spring back half of the stroke.  Same as handle.  The only bubbles I saw any time were at the end of the drain down.  Maybe time to call an expert. 

[N201MKTurbo]

So, with that info, I would check the check valves, probably the exit check valve. It may have a piece of stuff in it. This of course requires removing and disassembling the pump.

Don't feel bad that silly little pump has driven quite a few people crazy.

[Immelman]

Did you try bleeding from the flap slave up?

If your pump was working/not leaking before, I would try that. Opening the pump opens more possibilities.

[Pasturepilot]

Ok, this is a sliver of a memory of a post I read here once so don’t hold me to this. May have been Ross or someone else that posted. 

But..  I think the flap handle doesn’t move the pump through its entire range of motion. It can have air trapped in it that may only be released if you disconnect it from the handle and pump it though its entire stroke. 
 

I hope that’s correct, helpful, and makes sense. 

J

[Shadrach]

On 11/14/2020 at 5:38 AM, Pasturepilot said:

Ok, this is a sliver of a memory of a post I read here once so don’t hold me to this. May have been Ross or someone else that posted. 

But..  I think the flap handle doesn’t move the pump through its entire range of motion. It can have air trapped in it that may only be released if you disconnect it from the handle and pump it though its entire stroke. 
 

I hope that’s correct, helpful, and makes sense. 

J

I did not know this, so it definitely was not me. If true it would be an interesting quirk. It was always my supposition that pump and actuator were volume matched 1 to 4. 
My take on the OPs problem is that there is air in the system. I would have been inclined to to remove and inspect once drained as the mess of draining is the a big part of the hassle associated with system mx. 

Bleeding from the top is sub optimal. Bleeding from actuator yields better results.

 

1) Loosen the bleed screw 

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.

 

Here’s an old thread on bleeding.

 

Edited November 16, 2020 by Shadrach