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CJ6 low main pressure

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Harv

Joined: 01 Jul 2010
Posts: 172

Posted: Wed Jan 22, 2020 2:21 pm Post subject: CJ6 low main pressure

Good evening



Have a slight air issue on my CJ.



With system charged from external scuba bottle, pop off valve heard at 5kgcm gauge reading with main air closed but open the main air valve and pressure on gauge drops immediately to 2kgcm but holds steady at that point.



I've not done too much investigation as yet but welcome ideas with likely culprits.....



Looking at the CJ air schematic I see that there could be a leak from a few places.



1. Belly snot valve

2. Gear Rams (extend side)

3. Check valve on firewall 

4. QDF-1 Start valve

5. QS-1 Brake pressure reducing valve? (Do these leak to atmos?)



Thanks in advance.



Harv

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pennington.construction.i
Guest

Posted: Wed Jan 22, 2020 2:44 pm Post subject: CJ6 low main pressure

Harv



That all sounds normal to me.  If the main air valve is closed.  And you charge the system.  You are excluding the 12L main air bottle from the system.  

When you open the main air valve you put pressure on the main air tank.  That would look just like you see.  A pressure drop.

When charging the system with the external bottle have the main air valve open.  Charge the entire system.   Close the main air valve.  If your CJ is like most the air will bleed off to nothing over time.  

That’s normal.  (Wish it wasn’t )

When you open the main air valve.  It will charge the system.  When you start the plane. The compressor will fill the bottle and keep the system running.  

Mark Pennington

804 399 4224.  

N621 CJ

If you have questions feel free to call.  



On Wed, Jan 22, 2020 at 5:28 PM Harv <martin.harvey(at)kbr.com (martin.harvey(at)kbr.com)> wrote:



 	  Quote: 	
		  --> Yak-List message posted by: "Harv" <martin.harvey(at)kbr.com (martin.harvey(at)kbr.com)>

 

 Good evening

 

 Have a slight air issue on my CJ.

 

 With system charged from external scuba bottle, pop off valve heard at 5kgcm gauge reading with main air closed but open the main air valve and pressure on gauge drops immediately to 2kgcm?

 

 I've not done too much investigation as yet but welcome ideas with likely culprits.....

 

 Looking at the CJ air schematic I see that there could be a leak could be from a few places.

 

 1. Belly snot valve

 2. Gear Rams (extend side)

 3. Check valve on firewall 

 4. QDF-1 Start valve

 5. QS-1 Brake pressure reducing valve? (Do these leak to atmos?)

 

 Thanks in advance.

 

 Harv

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=494397#494397

 

 

 

 

 

 

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Clouddog

Joined: 02 Jun 2016
Posts: 119
Location: Lebanon, TN

Posted: Wed Jan 22, 2020 3:18 pm Post subject: CJ6 low main pressure

Mark is correct. With main air valve closed you will only charge the lines and the emergency tank. Remember to open main air valve when filling. Think of the main air valve as a shut off valve to main air tank only. Tank may be in the tail but the open valve (main shutoff valve) is in cockpit.



Also, when using scuba air to fill  system, crack the scuba valve and never open it fully. Your dealing with a 3000 psi scuba bottle dumping air into a 750 psi system. If the pop off valve can't react fast enough or fails to open, something is going to blow. Jump on the wing and watch the main air  and  emergncy air gages. In addition go to Doug's website and he has an Excellent schematic of the air system for download. I had it blown up 18x24 and laminated. Great in the hangar. Also on my phone for reference when on the road.

Lastly, Mark says the system bleeds down quickly. What he meant to add is in a perfect world when you shut the main air off you are isoalating the main tank from system and if all your check valves are working the air that bleeds off is what's trapped in the lines the main tank and emergency tank should stay full or to wherever the pop off valve is set.

Greg

On Wed, Jan 22, 2020, 17:48 Mark Pennington <pennington.construction.inc.1(at)gmail.com (pennington.construction.inc.1(at)gmail.com)> wrote:



 	  Quote: 	
		  Harv



That all sounds normal to me.  If the main air valve is closed.  And you charge the system.  You are excluding the 12L main air bottle from the system.  

When you open the main air valve you put pressure on the main air tank.  That would look just like you see.  A pressure drop.

When charging the system with the external bottle have the main air valve open.  Charge the entire system.   Close the main air valve.  If your CJ is like most the air will bleed off to nothing over time.  

That’s normal.  (Wish it wasn’t )

When you open the main air valve.  It will charge the system.  When you start the plane. The compressor will fill the bottle and keep the system running.  

Mark Pennington

804 399 4224.  

N621 CJ

If you have questions feel free to call.  



On Wed, Jan 22, 2020 at 5:28 PM Harv <martin.harvey(at)kbr.com (martin.harvey(at)kbr.com)> wrote:



 	  Quote: 	
		  --> Yak-List message posted by: "Harv" <martin.harvey(at)kbr.com (martin.harvey(at)kbr.com)>

 

 Good evening

 

 Have a slight air issue on my CJ.

 

 With system charged from external scuba bottle, pop off valve heard at 5kgcm gauge reading with main air closed but open the main air valve and pressure on gauge drops immediately to 2kgcm?

 

 I've not done too much investigation as yet but welcome ideas with likely culprits.....

 

 Looking at the CJ air schematic I see that there could be a leak could be from a few places.

 

 1. Belly snot valve

 2. Gear Rams (extend side)

 3. Check valve on firewall 

 4. QDF-1 Start valve

 5. QS-1 Brake pressure reducing valve? (Do these leak to atmos?)

 

 Thanks in advance.

 

 Harv

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=494397#494397

 

 

 

 

 

 

 ===========

 br> fts!)

 r> > rel="noreferrer" target="_blank">http://www.matronics.com/contribution

           -Matt Dralle, List Admin.

 ===========

 List" rel="noreferrer" target="_blank">http://www.matronics.com/Navigator?Yak-List

 ===========

  FORUMS -

 eferrer" target="_blank">http://forums.matronics.com

 ===========

 WIKI -

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 ===========

 b Site -

           -Matt Dralle, List Admin.

 rel="noreferrer" target="_blank">http://www.matronics.com/contribution

 ===========

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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pennington.construction.i
Guest

Posted: Wed Jan 22, 2020 4:11 pm Post subject: CJ6 low main pressure

Excellent Summation.  👍👍👍



Mark



On Wed, Jan 22, 2020 at 6:22 PM Greg Wrobel <clouddog22(at)gmail.com (clouddog22(at)gmail.com)> wrote:



 	  Quote: 	
		  Mark is correct. With main air valve closed you will only charge the lines and the emergency tank. Remember to open main air valve when filling. Think of the main air valve as a shut off valve to main air tank only. Tank may be in the tail but the open valve (main shutoff valve) is in cockpit.



Also, when using scuba air to fill  system, crack the scuba valve and never open it fully. Your dealing with a 3000 psi scuba bottle dumping air into a 750 psi system. If the pop off valve can't react fast enough or fails to open, something is going to blow. Jump on the wing and watch the main air  and  emergncy air gages. In addition go to Doug's website and he has an Excellent schematic of the air system for download. I had it blown up 18x24 and laminated. Great in the hangar. Also on my phone for reference when on the road.

Lastly, Mark says the system bleeds down quickly. What he meant to add is in a perfect world when you shut the main air off you are isoalating the main tank from system and if all your check valves are working the air that bleeds off is what's trapped in the lines the main tank and emergency tank should stay full or to wherever the pop off valve is set.

Greg

On Wed, Jan 22, 2020, 17:48 Mark Pennington <pennington.construction.inc.1(at)gmail.com (pennington.construction.inc.1(at)gmail.com)> wrote:



 	  Quote: 	
		  Harv



That all sounds normal to me.  If the main air valve is closed.  And you charge the system.  You are excluding the 12L main air bottle from the system.  

When you open the main air valve you put pressure on the main air tank.  That would look just like you see.  A pressure drop.

When charging the system with the external bottle have the main air valve open.  Charge the entire system.   Close the main air valve.  If your CJ is like most the air will bleed off to nothing over time.  

That’s normal.  (Wish it wasn’t )

When you open the main air valve.  It will charge the system.  When you start the plane. The compressor will fill the bottle and keep the system running.  

Mark Pennington

804 399 4224.  

N621 CJ

If you have questions feel free to call.  



On Wed, Jan 22, 2020 at 5:28 PM Harv <martin.harvey(at)kbr.com (martin.harvey(at)kbr.com)> wrote:



 	  Quote: 	
		  --> Yak-List message posted by: "Harv" <martin.harvey(at)kbr.com (martin.harvey(at)kbr.com)>

 

 Good evening

 

 Have a slight air issue on my CJ.

 

 With system charged from external scuba bottle, pop off valve heard at 5kgcm gauge reading with main air closed but open the main air valve and pressure on gauge drops immediately to 2kgcm?

 

 I've not done too much investigation as yet but welcome ideas with likely culprits.....

 

 Looking at the CJ air schematic I see that there could be a leak could be from a few places.

 

 1. Belly snot valve

 2. Gear Rams (extend side)

 3. Check valve on firewall 

 4. QDF-1 Start valve

 5. QS-1 Brake pressure reducing valve? (Do these leak to atmos?)

 

 Thanks in advance.

 

 Harv

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=494397#494397

 

 

 

 

 

 

 ===========

 br> fts!)

 r> > rel="noreferrer" target="_blank">http://www.matronics.com/contribution

           -Matt Dralle, List Admin.

 ===========

 List" rel="noreferrer" target="_blank">http://www.matronics.com/Navigator?Yak-List

 ===========

  FORUMS -

 eferrer" target="_blank">http://forums.matronics.com

 ===========

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 errer" target="_blank">http://wiki.matronics.com

 ===========

 b Site -

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 rel="noreferrer" target="_blank">http://www.matronics.com/contribution

 ===========

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Harv

Joined: 01 Jul 2010
Posts: 172

Posted: Wed Jan 22, 2020 11:28 pm Post subject: Re: CJ6 low main pressure

Thanks for the replies 



I should have added that I did open the main air at one point to charge the system but I fear my scuba bottle was somewhat depleted and couldn't bring the whole system to operating pressure as in the end I had it's valve fully open and couldn't hear leaking or pop the PRV. I've put the bottle in for service at the local dive shop, will try again and report back.



Touch wood my system has been very good since we rebuild it with stainless check valves, new flexible lines, snot pots and actuators in 2013 from Doug Sapp.



Happy flying



Harv

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