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Gear not coming up

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thomasg(at)infosysnetwork
Guest

Posted: Mon Apr 18, 2011 1:54 pm Post subject: Gear not coming up

Today when I talk my CJ for a flight I was unable to raise the gear. I got a short hissing sound and the right gear raised a little ( 1 line on the barber pole). I tried to cycle gear, no luck. Any suggestions on what to look at? I had 38 kg/cm2.



Thanks,

Tommy

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gill.g(at)gpimail.com
Guest

Posted: Mon Apr 18, 2011 2:43 pm Post subject: Gear not coming up

Tommy,



Yes, it is one or more of the shuttle valves that isolate the emergency air from the regular.  What is happening is that regular system air is leaking past the shuttle valve and back pressuring the emergency air side so that gear is locked down as would be the case when you intentionally use the emergency air.  Means you have to repair or replace one or all of your shuttle valves.  The problem can sometimes be intermittent.  So you can test this by releasing pressure on the emergency side by loosening the b-nut on the landing gear shuttle valve.  Personally, I went through that process and ultimately installed a 4 way valve which continuously bleeds the emergency side pressure and haven't had the problem since.



Gill



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dsavarese0812(at)bellsout
Guest

Posted: Mon Apr 18, 2011 4:21 pm Post subject: Gear not coming up

You will need to put the airplane on jacks to cycle the gear.  Does the 

emergency air hold pressure or does it leak down and if so, how much 

does it typically leak down over 1 day, 2 days, 3 days etc?  The reason 

for this question will be obvious in the 3rd paragraph.



You very well could have a leaking main gear actuator.  On the jacks you 

should be able to hear it hissing when you turn on the main air and move 

the gear selector to the UP position.  There may also be an audible leak 

with the gear down.  If you have air leaking out of the front gear 

selector, don't immediately assume it is the gear selector.  It again 

could very well be a leaking actuator.



Here's a test you can do.  First make sure both the main and emergency 

air valves are securely turned off.  Now bleed the system down by 

squeezing the brake handle until you don't hear any more "hissing" when 

you release the brake handle.  Now, with the airplane on the jacks, turn 

on the main air valve and immediately cycle the gear.  If the gear 

retracts normally, you have a leak from the emergency side to the main 

side through a check valve which moves the shuttle valves on the 

actuators blocking the main side from functioning.  Obtain a schematic 

and start disconnecting B nuts on the firewall where the emergency and 

main systems come together.  Make up a bottle of soapy water to spray on 

lines you open on check valves.  Watch for bubbles where there isn't 

suppose to be any.



Contact me off list and tell me what you've done and we'll work through it.

Dennis

On 4/18/2011 4:51 PM, Thomas Geoghegan wrote:

 	  Quote: 	
		   



 Today when I talk my CJ for a flight I was unable to raise the gear. I got a short hissing sound and the right gear raised a little ( 1 line on the barber pole). I tried to cycle gear, no luck. Any suggestions on what to look at? I had 38 kg/cm2.



 Thanks,

 Tommy

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Joe Enzminger

Joined: 06 Feb 2006
Posts: 26

Posted: Mon Apr 18, 2011 8:15 pm Post subject: Re: Gear not coming up

I would suggest a quick check of the rear cockpit gear handle.  If it has been bumped "down", or even partially down, it can prevent the gear from retracting when you select up in the front cockpit.



Something simple to check before you start removing check valves, etc.  



Joe

700YK

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dsavarese0812(at)bellsout
Guest

Posted: Tue Apr 19, 2011 4:30 am Post subject: Gear not coming up

Ahh...what a great suggestion Joe.  Good job.  That completely slipped 

my mind.

Dennis



On 4/18/2011 11:15 PM, Joe Enzminger wrote:

 	  Quote: 	
		   



 I would suggest a quick check of the rear cockpit gear handle.  If it has been bumped "down", or even partially down, it can prevent the gear from retracting when you select up in the front cockpit.



 Something simple to check before you start removing check valves, etc.



 Joe

 700YK





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