Positive Control not so Positive Right Now

[MBDiagMan]

I got my F back yesterday and my landing gear problem is now well sorted.  Form that standpoint I feel I can fly it with confidence that I won’t have to fly it gear down.

When I flew home I had 4” vacuum unless I pressed the PC button, then it went to 4.2.  It has a new vac pump so I think I just need to adjust the regulator to get it back in the 5” area, but the leveler was allowing right bank.  It seems clear that there is a leak in a hose or actuator.  I am thinking that since they worked on the ASS near the turn coordinator they may have bumped a hose loose.

in looking at the manual, I think I can find the actuators in the wings but are there also rudder actuators and where are they? The 

[Pasturepilot]

Open up the big panel on the right side of the fuselage behind the aft cabin bulkhead. They’re attached to the pushrod with cables. 

[Ron McBride]

When you taxi, the yoke should try to bank against the turn.  
Rudder servos are in the tail. 
 

There are hoses connected to the turn coordinator, might be knocked loose.   Also you have an adjustment knob, was it moved.

Ron

[MBDiagMan]

I turned the adjustment knob full travel and there was not enough compensation.  It still banked right.

[salty]

Sounds like a hose came off, is leaking,  or there's a tear in a boot.

[MBDiagMan]

Okay, there are a few things in play here beyond the PC system:

It got a new vac pump a few months ago, but now making only 4.2 inches.of vacuum.  I was told that the regulator needs to be adjusted up, but I can’t find anything that looks like an adjustable regulator.  I found the square valve that is part of the PC system and a round thing with what looks like a foam, cylindrical filter.  There was another round thing with hoses that said something like “Precise Mechanisms as a brand name.  I also found a loose hose on the back of the turn coordinator.  I fixed that and thought it was the leak, but no change.

[takair]

55 minutes ago, MBDiagMan said:

Okay, there are a few things in play here beyond the PC system:

It got a new vac pump a few months ago, but now making only 4.2 inches.of vacuum.  I was told that the regulator needs to be adjusted up, but I can’t find anything that looks like an adjustable regulator.  I found the square valve that is part of the PC system and a round thing with what looks like a foam, cylindrical filter.  There was another round thing with hoses that said something like “Precise Mechanisms as a brand name.  I also found a loose hose on the back of the turn coordinator.  I fixed that and thought it was the leak, but no change.

Regulator is on top of what looks like a foam cylinder.  I would try to find the leak before adjusting the regulator or you will soon be going in circles.  (Really bad PC humor). There are a few threads buried here with some techniques, but it can still be tedious if it is not an  obvious loose or broken line....although you can narrow it down by the direction of turn.

[MBDiagMan]

Thanks.  It is banking to the right.

[takair]

I would take a look at the right hand actuators.  In level flight, they are both under equal suction.  So, if turning right, the left ones have more suction than the right, so you may have a leak on the right side.  

[Yetti]

The hose run along the pilot side wall.   There is a T connector just before the baggage rear wall.    Probably the quickest way to figure things out is a mity mite hand vacuum pump and do a leak down test.

[MBDiagMan]

When I was investigating under the panel I saw a green and a red line.  I can remove the respective lines from the TC and apply vacuum there to check all the stuff in the fuselage and the wings.  I will keep everyone posted about what I find.

[Guest]

5 minutes ago, MBDiagMan said:

When I was investigating under the panel I saw a green and a red line.  I can remove the respective lines from the TC and apply vacuum there to check all the stuff in the fuselage and the wings.  I will keep everyone posted about what I find.

You can connect a vacuum gauge to the open end of the red or green vacuum then lift up on the aileron using the servo pot to creat a vacuum in the system.  Alternately, have an assistant place their thumb over the open end of the line and then lift up on the aileron feeling for a vacuum.

Or you can use the vacuum pump Yetti suggests above, connected the either of the lines.

Clarence

[MBDiagMan]

Thanks guys.  I plan on using a vacuum source tomorrow to determine if the leak is one of those lines, then go from there.  

[Hank]

38 minutes ago, MBDiagMan said:

Thanks guys.  I plan on using a vacuum source tomorrow to determine if the leak is one of those lines, then go from there.  

Please report back what you find.

[MBDiagMan]

Okay.  The leak is somewhere down the red line on the left.  I pulled the hatch below the left aileron actuator and the one by the battery.  I disconnected the line from the red rudder actuator.  I applied vacuum to that rudder pod and it seemed to build vacuum properly and hold tight.  Getting the line off of the aileron actuator is going to be a challenge.  The boot on that one looks really good.  It has a black hose that connects to a piece of red line that comes about 4 inches out of that actuator and apparently goes back the fuselage.  This black hose seemingly replaces the original hard red line.  Now I am curious where the other end of the black hose connects to the red hard line near the cockpit.

At least I know which side and have a trail to follow.

Also the hard red line that is in the back of the aileron actuator feels like it might be loose at the actuator, but I can’t get my hands on it well enough to know for sure.  That actuator will be difficult to deal with to test and if need be, to repair it.

[salty]

I’ve replaced both the aileron boots. There’s no trick other than embracing the suck and be patient. A small wrench and Someone with small hands helps. 

Edited December 16, 2019 by salty

[Vance Harral]

Before you implicate the boots and go through difficult gyrations to test them, remove the port side interior carpet panel in the baggage compartment and have a look at the PC lines behind them.  It will only take a few minutes.  The first leak we diagnosed in our PC system when we bought our airplane 16 years ago, was that the prior owner had driven one of the screws for the port side baggage compartment carpet panel directly into one of the PC lines!  In our airplane, the offending screw is positioned directly over where the lines run.  We repaired the line and left the screw out of the carpet panel on reassembly, as the remaining screws were more than sufficient to hold the panel.

[MBDiagMan]

Do you remove the actuator and replace the boot on the bench?

Are the rudder boots the same part number as the aileron boots?

Mine is a 67 model.  Where do I access the tee that appears to be at the rear of the left wing root?

Edited December 16, 2019 by MBDiagMan

[takair]

4 minutes ago, MBDiagMan said:

Do you remove the actuator and replace the boot on the bench?

Are the rudder boots the same part number as the aileron boots?

Yes. Remove and replace on bench and they are the same. Hard part is getting new boots. Be careful with them.
 

I have to think through my previous idea that problem is on right side. Hope it didn’t waste too much time. 

[salty]

The boot is the actuator. It’s one piece. 

[MBDiagMan]

29 minutes ago, takair said:

Yes. Remove and replace on bench and they are the same. Hard part is getting new boots. Be careful with them.
 

I have to think through my previous idea that problem is on right side. Hope it didn’t waste too much time. 

No time wasted.  I just disconnected the lines at the TC and checked them.  That clearly pointed me toward the left side.  No harm no foul and I appreciated the attempt to help.

[MBDiagMan]

You know guys, when I was messing around behind the actuator the red line on the back of the boot seemed really loose.  Now that I am looking at the drawings showing how it all goes together I am thinking that might be the leak.  I’m buried in Getting ready for three daughters, three son in laws and nine Grandkids coming for Christmas.  If I can get a break from that I’m going back to the hangar and try to get my hand further behind there.  My hands are too big to fit in there.  I may have to take a grandkid to the hangar.

[chriscalandro]

If you have the panel in front of the windshield that might be easier access than underneath. Going under there is a painful nightmare and I’m in my early 30s. 

[MBDiagMan]

I am getting under the panel without too much trouble, but getting at the aileron actuator is tougher.  It has a J windshield and entire front cowling so there are no access panels in front of the windshield.  I did remove the panel top For  access to adjust the vacuum regulator.   Which way do I turn on the serrated knob atop the regulator to increase the vacuum?  The nut underneath that knob is not a locknut is it?

I got a few minutes at the hangar.  I disconnected the soft line from the red hard line on the left aileron and connected the vac source.  The red line to the TC was removed and plugged.  It would not hold a vacuum.  I did not have time to connect to the actuator itself and test it.

To be continued....

Edited December 16, 2019 by MBDiagMan

[Guest]

3 hours ago, MBDiagMan said:

I am getting under the panel without too much trouble, but getting at the aileron actuator is tougher.  It has a J windshield and entire front cowling so there are no access panels in front of the windshield.  I did remove the panel top For  access to adjust the vacuum regulator.   Which way do I turn on the serrated knob atop the regulator to increase the vacuum?  The nut underneath that knob is not a locknut is it?

I got a few minutes at the hangar.  I disconnected the soft line from the red hard line on the left aileron and connected the vac source.  The red line to the TC was removed and plugged.  It would not hold a vacuum.  I did not have time to connect to the actuator itself and test it.

To be continued....

The lock nut (5/8”) is loosened, then the serrated knob is turned to the right to increase vacuum and left to decrease vacuum.

Clarence