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Adjusting Emergency Air Pressure in a CJ?
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N642K

Joined: 23 Jul 2008
Posts: 84

Posted: Thu Sep 11, 2008 7:47 am Post subject: Adjusting Emergency Air Pressure in a CJ?

Ok, I have a new water separator and the correct main air dialed in (it had been way too high).  The emerg pressure has remained exactly where it was.  Is there another adjustment?  



Thanks.

keithmckinley

Joined: 11 Aug 2008
Posts: 434

Posted: Thu Sep 11, 2008 8:13 am Post subject: Re: Adjusting Emergency Air Pressure in a CJ?

I just did the exact same thing and adjusted my air to 43 ATM. Before I did that, however, I bleed down the emergency bottle. It's running a tad higher than the main pressure but I believe that is fairly normal. I don't believe, as a previous post suggests, that it is due to the bottle sizes. If the emergency bottle was bleed to zero it makes sense that it should never go higher than the pop off valve setting.



Of course there is the issue of gauge accuracy as well.



Keith

N700hs

N642K

Joined: 23 Jul 2008
Posts: 84

Posted: Thu Sep 11, 2008 8:15 am Post subject: Re: Adjusting Emergency Air Pressure in a CJ?

Thanks Keith, but how do you bleed it down? Is it just a cracking of the emergency air valve?

dougsappllc(at)gmail.com
Guest

Posted: Thu Sep 11, 2008 8:33 am Post subject: Adjusting Emergency Air Pressure in a CJ?

On a CJ6 the only pressure adjustment is the H2-5502-00 "pop of valve".  Both the main and emergency air tanks fill at the same time and BOTH are limited as to their pressure by the setting of this valve. So if your system is plumbed "normally" (no aftermarket changes in the system) all the gauges (all are P/N BYQ80-1A) should read the same 45 to 50 ATMS.  The key here is to first make sure your main air gauge is correct and reads 45 to 50 ATMS when your pop off valve starts relieving the pressure.  Then and only then can be secure in the knowledge that if your emergency gauges read higher, the problem is simply a bad gauge and not a potentially dangerous situation.

   

 Hope this helps.

  

 Always Yakin,

 Doug

 

 

 On Thu, Sep 11, 2008 at 8:47 AM, N642K <mdecanio(at)mac.com (mdecanio(at)mac.com)> wrote:

 [quote]--> Yak-List message posted by: "N642K" <mdecanio(at)mac.com (mdecanio(at)mac.com)>

 

Ok, I have a new water separator and the correct main air dialed in (it had been way too high).  The emerg pressure has remained exactly where it was.  Is there another adjustment?



Thanks.





Read this topic online here:

  [quote][b]

cjpilot710(at)aol.com
Guest

Posted: Thu Sep 11, 2008 8:33 am Post subject: Adjusting Emergency Air Pressure in a CJ?

In a message dated 9/11/2008 12:17:06 P.M. Eastern Daylight Time,  mdecanio(at)mac.com writes:

  

 Simply by loosening the "B" nut on the down stream of the check valve  which is on the firewall.  You'll hear the air escaping.  After the  pressure goes to zero, simply re tighten the "B" nut - safety wire it - and  you're good to go.

  

 Pappy

  	  Quote: 	
		  -->    Yak-List message posted by: "N642K" <mdecanio(at)mac.com>



Thanks    Keith, but how do you bleed it down?





Read this topic online    here:



http://forums.matronics.com/viewtopic.php?p=203823#203823

	


 

  



Psssst...Have you heard the news? There's a new fashion blog, plus the latest fall trends and hair styles at StyleList.com.

  [quote][b]

wlannon(at)persona.ca
Guest

Posted: Thu Sep 11, 2008 8:45 am Post subject: Adjusting Emergency Air Pressure in a CJ?

The charging air into the emergency tank goes through a non-return check 

valve on the RH side of the CJ firewall. If it has previously been charged 

to a higher value than the current relief valve setting there can be no 

change to the emerg. pressure since the check valve will not open.



If that is the case you must bleed some pressure from the emerg. tank by 

loosening a fitting at the check valve, the tank or at either valve.  If at 

the valve find the pipeline going to the tank.



Walt

---

dougsappllc(at)gmail.com
Guest

Posted: Thu Sep 11, 2008 8:56 am Post subject: Adjusting Emergency Air Pressure in a CJ?

Sorry guys, I should have specified that you need to start with empty tanks to do the process correctly.  Thanks Walt!

  

 Doug

 On Thu, Sep 11, 2008 at 9:39 AM, Walter Lannon <wlannon(at)persona.ca (wlannon(at)persona.ca)> wrote:

 [quote]--> Yak-List message posted by: Walter Lannon <wlannon(at)persona.ca (wlannon(at)persona.ca)>

 

The charging air into the emergency tank goes through a non-return check valve on the RH side of the CJ firewall. If it has previously been charged to a higher value than the current relief valve setting there can be no change to the emerg. pressure since the check valve will not open.

 

If that is the case you must bleed some pressure from the emerg. tank by loosening a fitting at the check valve, the tank or at either valve.  If at the valve find the pipeline going to the tank.



Walt

---

wlannon(at)persona.ca
Guest

Posted: Thu Sep 11, 2008 9:12 am Post subject: Adjusting Emergency Air Pressure in a CJ?

Typically I find that the emerg. air pressure will gradually creep up to 

about 5 ATM more than the main air.

As mentioned in a previous post I suggested this was due to difference in 

the size of the two systems (not the tanks.).  The main system includes 

landing gear, flaps, brakes and air start with all the various pipelines, 

fittings, actuators, shuttle valves, check-valves, flare joints, etc, etc.

By comparison, with the ermerg. valves closed,  the emerg. "system" consists 

of one tank, two pipelines and one check valve.

Is it any wonder the Emergency side is far less susceptible to leakage than 

the Main?



Not really necessary to reduce the emerg. pressure to zero. Anything lower 

than the relief valve setting will do.



Walt

---

keith(at)mckinley.us
Guest

Posted: Thu Sep 11, 2008 9:18 am Post subject: Adjusting Emergency Air Pressure in a CJ?

bleed the main air bottle and close the valve then open the emergency  

valve and cycle the flaps. It takes a bit to do it but it only needs  

to be less than the pressure you intend to set on the pop off valve.



Keith

On Sep 11, 2008, at 12:15 PM, N642K wrote:



 	  Quote: 	
		   



 Thanks Keith, but how do you bleed it down?





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 3823#203823

keithmckinley

Joined: 11 Aug 2008
Posts: 434

Posted: Thu Sep 11, 2008 9:25 am Post subject: Re: Adjusting Emergency Air Pressure in a CJ?

All the posts regarding loosening fittings to relieve pressure are fine but I guess I just hate to loosen and re-tighten if it isn't leaking and I can do it by other means.



That's just me.



btw, I stand corrected on Walt's post regarding the system vs the bottles on the emergency side of things



Keith

N642K

Joined: 23 Jul 2008
Posts: 84

Posted: Thu Sep 11, 2008 9:37 am Post subject: Re: Adjusting Emergency Air Pressure in a CJ?

Thanks for all the helpful suggestions.

dsavarese0812(at)bellsout
Guest

Posted: Thu Sep 11, 2008 10:19 am Post subject: Adjusting Emergency Air Pressure in a CJ?

Don't forget, the shuttle valves for the landing gear actuators will move to 

the opposite side if you open the emergency valve.  To insure the landing 

gear will operate properly after you close the emergency air valve, you must 

bleed off the pressure on the emergency side of the shuttle valves.  If you 

don't do this, there is a very good chance the landing gear will not 

function properly.



Walt's suggestion for bleeding the emergency system down is the way you 

should do it.  That way you won't have to deal with the shuttle valves.

Dennis



---

keithmckinley

Joined: 11 Aug 2008
Posts: 434

Posted: Thu Sep 11, 2008 11:53 am Post subject: Re: Adjusting Emergency Air Pressure in a CJ?

Respectfully, I can't really think of a way that there would be a problem unless there was a faulty shuttle valve. And you can hear in move back and forth. But in any case a good reason to make sure the gear is cycled on the emergency bottle while on jacks for the annual.



K

dsavarese0812(at)bellsout
Guest

Posted: Thu Sep 11, 2008 1:58 pm Post subject: Adjusting Emergency Air Pressure in a CJ?

With pressure on the shuttle valve from the emergency side, the ball in the 

shuttle valve moves to the other side blocking off the main side.

Dennis



---

dsavarese0812(at)bellsout
Guest

Posted: Thu Sep 11, 2008 2:16 pm Post subject: Adjusting Emergency Air Pressure in a CJ?

ie: we have counter acting pressure on the shuttle valve.  The emergency 

system pressure has already moved the ball in the shuttle valve.  The main 

system pressure would be trying to move the ball the other way, but can't.



Try it sometime.  Put the airplane on jacks and raise the landing gear.  Now 

use the procedure for extending the gear with the emergency air.  Once the 

gear is down using the emergency air, try raising the gear normally.  If the 

gear won't go up it's because the ball shuttle valves to the actuators are 

moved to the opposite side by the pressure from the emergency system. 

Unless you relieve that pressure, the ball will stay there blocking the main 

side from functioning properly.



Walt Lannon - would you like to comment on this?

Dennis



---

Dabear(at)damned.org
Guest

Posted: Thu Sep 11, 2008 2:59 pm Post subject: Adjusting Emergency Air Pressure in a CJ?

However,  you can remove the air from the emergency side by closing the 

emergency valve (engine/compressor not running), and actuating the 

flaps/gear/brakes.  Once the air is out of the emerg side of the system the 

gear can be raised again.  One of the biggest issues I have seen over the 

years is coming out of annual, once the emerg gear extension is done.  It 

causes problems with the air system because the shuttle valves have moved 

for the first time in a year.  Any issues/weaknesses with the shuttle valves 

will be seen just after annual.



I'm wondering if I want to test the emergency system every month or so to 

limit the issues.  Thoughts?



DaBear

---

randmyak52(at)bellsouth.n
Guest

Posted: Thu Sep 11, 2008 4:03 pm Post subject: Adjusting Emergency Air Pressure in a CJ?

No!

---

wlannon(at)persona.ca
Guest

Posted: Thu Sep 11, 2008 7:15 pm Post subject: Adjusting Emergency Air Pressure in a CJ?

Hi Dennis;



Sorry, just got home.

In my opinion you are correct. At every annual after the emergency gear down 

test I bleed the air from each actuator to ensure the next gear retraction 

will be normal. It takes about 5 minutes.

It can be done by operating the brakes and flaps but may take up to 30 

minutes to ensure the emergency down pressure system is reduced to zero. 

Even then you would be wise to do a normal gear cycle while still on the 

jacks.



Cheers;

Walt

---

keithmckinley

Joined: 11 Aug 2008
Posts: 434

Posted: Thu Sep 11, 2008 7:32 pm Post subject: Re: Adjusting Emergency Air Pressure in a CJ?

Gents,



This exchange was great! It has really helped educate me on the air system. When can we start on the electrical system!   



Keith

dsavarese0812(at)bellsout
Guest

Posted: Fri Sep 12, 2008 3:03 am Post subject: Adjusting Emergency Air Pressure in a CJ?

Yes, that is 100% true.  The key point is you must relieve the pressure on 

the emergency side or the gear will not operate properly.  That why the 

original post of opening the emergency knob to reduce the pressure in the 

emergency tank is not, in my opinion anyway, the best way to reduce the air 

pressure because of exactly the reasons stated.  Crack one of the B-nuts and 

you won't have the possibility of not being able to retract the landing 

gear.

Dennis



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