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gear problem

 
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talew(at)bellsouth.net
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PostPosted: Mon Jan 30, 2006 7:34 pm    Post subject: gear problem Reply with quote

Has anyone seen this problem before?
The left main gear will not retract unless I go to neutral then pull the handle up.
I have checked all of the shuttle valves in the left gear system.They
test OK. The actuator will extend at  45 psi when out of the aircraft with no leaks. I changed the check valve on the firewall below the air filter that was corroded. It needed to be changed but it was not a fix.I am running out of ideas.
I am thinking I have a blockage in the return of the extend pressure,however I haven't found it yet.
Terry Lewis


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wlannon(at)cablerocket.co
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PostPosted: Mon Jan 30, 2006 10:51 pm    Post subject: gear problem Reply with quote

Terry;
 
Is this a CJ or 52?.
I assume a CJ but this part of the system is probably the same. The usual reason for this  problem is air pressure in the down side of the retract cylinder.
Could be internal leakage in the check valve (on the firewall) that stops the normal system from pressurizing the emerg. system. Usually a corroded valve and spring. But generally with this problem none of the gear would retract.
If that happens the pressure in the emergency system goes directly (not through the gear control valves) to the down side of the actuators and will be trapped there.
Easy to test.Remove the line to the emerg side, pressurize the main system and check for air leakage at the emerg. port,
Also could be a failed seal inside the retract cylinder. With it on the bench and in the gear up position is there any leakage from the down port with pressure in the up side.
 
Also the possibility of a failing uplock release valve or it's associated emergency diverter valve.
 
Good luck;
Walt 
 
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cjpilot710(at)aol.com
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PostPosted: Tue Jan 31, 2006 5:07 am    Post subject: gear problem Reply with quote

Terry,
 
Walt makes some good points.  But I would check your gear handle valve.  Me thinks, that with the gear working AFTER you've put the handle in neutral (dumping all pressure), that you may have a problem there in that the face of the valve may be scratched or corroded allowing pressure to cross even if the valve moved to the up side.
 
Also might want to recheck that emergency shuttle valve.  If you can sake it and hear the valve spring back and forth, it's good.  If that valve is not seated just a little bit, the gear will not re track.
 
Jim "Pappy" Goolsby


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gus.fraser(at)gs.com
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PostPosted: Tue Jan 31, 2006 5:33 am    Post subject: gear problem Reply with quote

Emergency shuttle valve gets my vote, I had exactly the same issue and that was it.
 
Gus

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From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of cjpilot710(at)aol.com
Sent: Tuesday, January 31, 2006 8:04 AM
To: yak-list(at)matronics.com
Subject: Re: gear problem

Terry,
 
Walt makes some good points.  But I would check your gear handle valve.  Me thinks, that with the gear working AFTER you've put the handle in neutral (dumping all pressure), that you may have a problem there in that the face of the valve may be scratched or corroded allowing pressure to cross even if the valve moved to the up side.
 
Also might want to recheck that emergency shuttle valve.  If you can sake it and hear the valve spring back and forth, it's good.  If that valve is not seated just a little bit, the gear will not re track.
 
Jim "Pappy" Goolsby


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rvfltd(at)televar.com
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PostPosted: Wed Feb 01, 2006 5:38 pm    Post subject: gear problem Reply with quote

Terry, I am sure it is your diverter valves, somehow air is leaking into the back side of the system.  If someone has been messing with your emergency air cock this will also cause the same or worse problem but that is easily fixed by bleeding the air off the system. 
 
If you require them, I have all the small parts necessary to overhaul the shuttle valves, or new valves if you want to go that way.  Be VERY careful when taking off the end cap as they are normally really tight and take a bunch of torque to break them loose.  Squeeze it to tight in the vise and you will oblong the housing and the shuttle will not work properly, if it's too loose it will spin in the vise and will "two block" the center fitting and break it off.  All is not lost as I have them also, but just go slowly and you won't have a problem.  
 
Another word of caution, check your desiccant air dryer, if you diverter valves are nasty you most likely have a problem in you dryer.  Give me a call at 509-826-4610 if you have any questions.
 
Good luck
 

Always Yakin,
Doug Sapp [quote] --


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talew(at)bellsouth.net
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PostPosted: Thu Feb 02, 2006 9:07 am    Post subject: gear problem Reply with quote

First let me thank the folks who offered advise.
 I did find that I needed the check valve on the firewall but that didn't fix the problem. All the other check valves and shuttle valves were fine.
What I found after blowing out the lines to the rear gear valve was that I had a restrictor in the left gear line but no restrictor in the right gear line.
This restrictor had hole of about .0030 in and could have been blocked by a grain of sand or such. I removed the restrictor and the problem is gone!
Again, Thanks for the help.
Terry Lewis


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dsavarese(at)elmore.rr.co
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PostPosted: Thu Feb 02, 2006 12:21 pm    Post subject: gear problem Reply with quote

The restrictors are used to reduce the flow, not the pressure.  Removing the restrictor only causes the landing gear to move way to rapidly, much like blowing the gear down with the emergency system, which has no restrictors in the lines.  My suggestion is to put them back in place.  FWIW.
Dennis
 
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