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Low Emergency Air Pressure
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wlannon(at)persona.ca
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PostPosted: Wed Sep 07, 2011 7:43 am    Post subject: Low Emergency Air Pressure Reply with quote

Thanks Mark;
Another reminder that one can not assume any particular similarity between the various models.
Walt
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yakplt(at)yahoo.com
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PostPosted: Wed Sep 07, 2011 8:38 am    Post subject: Low Emergency Air Pressure Reply with quote

Brian, I am not sure how you could away with any of these check valves and keep system isolation. You have two input air sources, and you have two bottles. Each air input needs to be isolated from each other and each bottle needs to be isolated from each other. How could you get away with less?



Mark



From: Brian Lloyd <brian(at)lloyd.com>
To: yak-list(at)matronics.com
Sent: Wednesday, September 7, 2011 10:57 AM
Subject: Re: Low Emergency Air Pressure

Has anyone else noticed that there are a lot more check valves in our airplanes than are needed to ensure system integrity after a partial failure? While helping Dennis Nickson troubleshoot an intermittent problem with the pneumatic system in his CJ it was pretty obvious that I could replace several of the check valves with straight pipe and it would have no effect on either the normal operation or how the system would fail if it was breached at various places. And I suspect that pieces of straight pipe are less likely to fail and cause problems than the various unnecessary check valves.


I am thinking that, right after removing and throwing away the arcane and unnecessary complexity of the electrical system, we could probably to do the same for much of the pneumatic system as well. Smile

--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
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yakplt(at)yahoo.com
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PostPosted: Wed Sep 07, 2011 8:39 am    Post subject: Low Emergency Air Pressure Reply with quote

It always surprises me to see the differences between the YAK-50 and 52, and then turn right around and find exact matches with the CJ-6. Especially with the actual parts themselves.

Mark


From: Walter Lannon <wlannon(at)persona.ca>
To: yak-list(at)matronics.com
Sent: Wednesday, September 7, 2011 11:41 AM
Subject: Re: Yak-List: Low Emergency Air Pressure

Thanks Mark;
Another reminder that one can not assume any particular similarity between the various models.
Walt


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brian(at)lloyd.com
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PostPosted: Wed Sep 07, 2011 8:52 am    Post subject: Low Emergency Air Pressure Reply with quote

On Wed, Sep 7, 2011 at 9:37 AM, Yak Pilot <yakplt(at)yahoo.com (yakplt(at)yahoo.com)> wrote:
Quote:


It always surprises me to see the differences between the YAK-50 and 52, and then turn right around and find exact matches with the CJ-6.� Especially with the actual parts themselves.�


The Chinese never throw anything away. They just keep using it forever. And they never let anyone else's work evade their eyes either. Wink

--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)

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brian(at)lloyd.com
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PostPosted: Wed Sep 07, 2011 9:06 am    Post subject: Low Emergency Air Pressure Reply with quote

On Wed, Sep 7, 2011 at 9:35 AM, Yak Pilot <yakplt(at)yahoo.com (yakplt(at)yahoo.com)> wrote:
Quote:
Brian, I am not sure how you could away with any of these check valves and keep system isolation.� You have two input air sources, and you have two bottles.� Each air input needs to be isolated from each other and each bottle needs to be isolated from each other.� How could you get away with less?




Maybe you need to look at the CJ6A pneumatic system, which is what I was dealing with when troubleshooting and making my observations.
The problem is, while the check valves ostensibly provide isolation, they don't really because there really is only a single source of pressure in the entire system. So a failure in any subsystem results in depressurization of the entire system. Yes, it is possible that, if you already have the gear down some of those check-valves might hold the pressure in the down-circuit there is no separate storage in the gear circuit to allow you to still put the gear down. So the backup/emergency system really is the only solution, thus making almost all the check-valves in main system superfluous.�


You can repeat my thought experiment. Take the pneumatic system schematic, imagine system breaches at different points, and then see what the effect is on the rest of the system. Now repeat the process while removing various check valves from the schematic. I think you will find that in VERY few cases do the check valves allow the rest of the system to continue to work. The only real answer is the emergency system.


OTOH, I also got see how check valves fail. If not properly maintained (and a lot of them are not properly maintained) the carbon-steel springs corrode, fail, and spread pieces of rust through the system. The funny thing is, even with the failed check valves, the system operates normally, except when the rust gets into things like valves and actuators. Wink


Now it has been awhile since I looked at the schematic for the Yak-52 pneumatic system so perhaps my points are less valid for that system.
But never underestimate the power of KISS. Remember, when something isn't there it can't fail.

--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)

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Rob Rowe



Joined: 10 Jan 2006
Posts: 124
Location: Berkshire, UK

PostPosted: Wed Sep 07, 2011 11:15 am    Post subject: Re: Low Emergency Air Pressure Reply with quote

Hi Brian,

Interesting thought exercise ... the YAK-52 designers seem to have beaten us to it, in as much as there are fewer pneumatic check valves (NRVs) than those of its near & far relations.

Skip this next bit if you're easily bored ;-)

Air charging NRVs:
Main - failure dumps main system pressure overboard [essential]
Reserve - ditto for emergency air [essential]
Compressor (feeds main) - failure dumps system pressure on opening snot valve [highly desirable!]
Pressure Relief Valve (PRV) - failure open dumps main system pressure overboard or failure closed over pressures system [essential]

Protection Valve - needed to EASILY depressurise emergency system after use (you could just keep pumping the brakes though) & stop seepage operating emergency gear systems [highly desirable]

Brake Valve feed NRVs:
Main - allows use of emergency air in event of main air failure [essential]
Reserve - failure cross-feeds air into emergency systems ... another reason why the Protection Valve is fitted for minor leaks, but drains main air down. Major leaks would protect main air while simultaneously trying to activate emergency gear down ... nasty! [essential]

Air 'Off' Start Protection (UK mandated mod) - helps prevent engine start with air off (so no brakes either) by preventing gear system back pressure from being used to start engine. [useful, but superfluous]
What surprises me though is how many ways they've found to use the same components, plumbed in different configurations, to perform ostensibly the same operational function across these aircraft ... an area where system standardisation would really have paid dividends from a pilot's perspective.

Edit #1 - corrected brake reserve NRV failure consequences

Edit #2 - added PRV failure

Brgds, Rob R
brian(at)lloyd.com wrote:


Maybe you need to look at the CJ6A pneumatic system, which is what I was dealing with when troubleshooting and making my observations.
The problem is, while the check valves ostensibly provide isolation, they don't really because there really is only a single source of pressure in the entire system. So a failure in any subsystem results in depressurization of the entire system ... So the backup/emergency system really is the only solution, thus making almost all the check-valves in main system superfluous.�


You can repeat my thought experiment. Take the pneumatic system schematic, imagine system breaches at different points, and then see what the effect is on the rest of the system. Now repeat the process while removing various check valves from the schematic. I think you will find that in VERY few cases do the check valves allow the rest of the system to continue to work. The only real answer is the emergency system.

... Now it has been awhile since I looked at the schematic for the Yak-52 pneumatic system so perhaps my points are less valid for that system.

...
--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)



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Last edited by Rob Rowe on Wed Sep 07, 2011 11:49 am; edited 1 time in total
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philg



Joined: 29 Jul 2010
Posts: 2
Location: Toowoomba, Australia

PostPosted: Wed Sep 07, 2011 11:30 am    Post subject: Re: Low Emergency Air Pressure Reply with quote

In the case of my Aircraft (yak-18t) it turned out to be a pinhole leak in the bottom of the emergency bottle through the weld - had to purchase a new bottle from WLAC in the UK. Talking to the local CFI the other day reveals that a similar leak found in 2 other a/c on the field, one a yak-52 and the other a CJ6! One other thing to check. Cheers, Phil.

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yakplt(at)yahoo.com
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PostPosted: Wed Sep 07, 2011 11:38 am    Post subject: Low Emergency Air Pressure Reply with quote

Too many airplanes to discuss at once Brian. YAK-52 is not the same as YAK-50. CJ-6 is yet another topic. The check valves in the 50 system make perfect sense. Emergency bottle and Main bottle are resevoirs and thus are sources unto themselves. This becomes a discussion of semantics and that is not something I am interested in going into honestly. In flight, the compressor is actually a renewable source not a single source. The check valves in the 50 design prevent any single source of failure from preventing gear extension. Removing any of them will remove that feature, which is obviously to be avoided. I am not an expert on the CJ-6 or the YAK-52, so I can't speak to those topics. I believe the YAK-50 design is excellent and does it's job perfectly, and I do not believe it can be done any better with removal of any components.

Just saying.

Mark




From: Brian Lloyd <brian(at)lloyd.com>
To: yak-list(at)matronics.com
Sent: Wednesday, September 7, 2011 1:01 PM
Subject: Re: Low Emergency Air Pressure



On Wed, Sep 7, 2011 at 9:35 AM, Yak Pilot <yakplt(at)yahoo.com (yakplt(at)yahoo.com)> wrote:
Quote:
Brian, I am not sure how you could away with any of these check valves and keep system isolation. You have two input air sources, and you have two bottles. Each air input needs to be isolated from each other and each bottle needs to be isolated from each other. How could you get away with less?


Maybe you need to look at the CJ6A pneumatic system, which is what I was dealing with when troubleshooting and making my observations.


The problem is, while the check valves ostensibly provide isolation, they don't really because there really is only a single source of pressure in the entire system. So a failure in any subsystem results in depressurization of the entire system. Yes, it is possible that, if you already have the gear down some of those check-valves might hold the pressure in the down-circuit there is no separate storage in the gear circuit to allow you to still put the gear down. So the backup/emergency system really is the only solution, thus making almost all the check-valves in main system superfluous.�


You can repeat my thought experiment. Take the pneumatic system schematic, imagine system breaches at different points, and then see what the effect is on the rest of the system. Now repeat the process while removing various check valves from the schematic. I think you will find that in VERY few cases do the check valves allow the rest of the system to continue to work. The only real answer is the emergency system.


OTOH, I also got see how check valves fail. If not properly maintained (and a lot of them are not properly maintained) the carbon-steel springs corrode, fail, and spread pieces of rust through the system. The funny thing is, even with the failed check valves, the system operates normally, except when the rust gets into things like valves and actuators. Wink


Now it has been awhile since I looked at the schematic for the Yak-52 pneumatic system so perhaps my points are less valid for that system.


But never underestimate the power of KISS. Remember, when something isn't there it can't fail.

--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)

[quote]

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brian(at)lloyd.com
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PostPosted: Wed Sep 07, 2011 11:53 am    Post subject: Low Emergency Air Pressure Reply with quote

On Wed, Sep 7, 2011 at 12:15 PM, Rob Rowe <yak-list(at)robrowe.plus.com (yak-list(at)robrowe.plus.com)> wrote:
Quote:
--> Yak-List message posted by: "Rob Rowe" <yak-list(at)robrowe.plus.com (yak-list(at)robrowe.plus.com)>

Hi Brian,

Interesting thought exercise ... the YAK-52 designers seem to �have beaten us to it, in as much as there are fewer pneumatic check valves (NRVs) than those of its near & far relations.


That well could be. It has been quite some time since I have studied the Yak-52 pneumatic diagram.

Quote:

Skip this next bit if you're easily bored Wink


No worries. I love the details.

Quote:

Air charging NRVs:
Main - failure dumps main system pressure overboard [essential]
Reserve - ditto for emergency air [essential]
Compressor (feeds main) - failure dumps system pressure on opening snot valve [highly desirable!]

Protection Valve - needed to EASILY depressurise emergency system after use (you could just keep pumping the brakes though) & stop seepage operating emergency gear systems [highly desirable]


Are you talking about a check valve or the shuttle valve that is used to automatically select system source (main or emergency)?
In many cases the problem is not one of preventing flow back into an upstream [sub]system that has failed but that forward flow into a failed subsystem still drains the source, making the overall pneumatic systems unusable.�

Quote:

Brake Valve feed NRVs:
Main - allows use of emergency air in event of main air failure [essential]
Reserve - failure cross-feeds air into emergency systems on operating brakes ... another reason why the Protection Valve is fitted [highly desirable]

Air 'Off' Start Protection (UK mandated mod) - helps prevent engine start with air off (so no brakes either) by preventing gear system back pressure from being used to start engine. [useful, but superfluous]


Yes. That sort of thing introduces an additional point of failure that is hard to detect and gains you very little.
But you may find that two or more of these valves that you have listed as essential, can have their functions�fulfilled�by a single, strategically-place check valve.


Quote:
What surprises me though is how many ways they've found to use the same components, plumbed in different configurations, to perform ostensibly the same operational function across these aircraft ... an area where system standardisation would really have paid dividends from a pilot's perspective.


That is also true.

--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)

[quote][b]


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brian(at)lloyd.com
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PostPosted: Wed Sep 07, 2011 11:55 am    Post subject: Low Emergency Air Pressure Reply with quote

On Wed, Sep 7, 2011 at 12:36 PM, Yak Pilot <yakplt(at)yahoo.com (yakplt(at)yahoo.com)> wrote:
Quote:
Too many airplanes to discuss at once Brian.� YAK-52 is not the same as YAK-50.� CJ-6 is yet another topic.�� The check valves in the 50 system make perfect sense.� Emergency bottle and Main bottle are resevoirs and thus are sources unto themselves.� This becomes a discussion of semantics and that is not something I am interested in going into honestly.� In flight, the compressor is actually a renewable source not a single source.� The check valves in the 50 design prevent any single source of failure from preventing gear extension.� Removing any of them will remove that feature, which is obviously to be avoided.� I am not an expert on the CJ-6 or the YAK-52, so I can't speak to those topics.� I believe the YAK-50 design is excellent and does it's job perfectly, and I do not believe it can be done any better with removal of any components.�


I don't doubt your word a bit. My comments were pretty much limited to the CJ6A since I have no knowledge of the Yak-50 pneumatic system and my knowledge of the Yak-52 is old.

--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)

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Vic



Joined: 12 Aug 2008
Posts: 116
Location: Southern Bavaria

PostPosted: Wed Sep 07, 2011 2:23 pm    Post subject: Re: Low Emergency Air Pressure Reply with quote

Hi all,

don´t forget to check the pipe / hose which connects the emergency bottle with the pressure gauge in the cockpit. When this fails you loose all air. We had a tiny leak in this particular hose of our 18 T as no one had changed it for ages.
Good luck on this one !

Cheers

Vic


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cjpilot710(at)aol.com
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PostPosted: Wed Sep 07, 2011 4:10 pm    Post subject: Low Emergency Air Pressure Reply with quote

Old Chinese saying - "Why reinvent wheel? It work good. Besides spend less time at drawing board."
Pappy



In a message dated 9/7/2011 12:39:44 P.M. Eastern Daylight Time, yakplt(at)yahoo.com writes:
Quote:

It always surprises me to see the differences between the YAK-50 and 52, and then turn right around and find exact matches with the CJ-6. Especially with the actual parts themselves.

Mark


From: Walter Lannon <wlannon(at)persona.ca>
To: yak-list(at)matronics.com
Sent: Wednesday, September 7, 2011 11:41 AM
Subject: Re: Yak-List: Low Emergency Air Pressure

Thanks Mark;
Another reminder that one can not assume any particular similarity between the various models.
Walt


Quote:


="http://www.matronics.com/Navigator?Yak-List">http://www.matronics.com/Navigator?Yak-List
s.matronics.com/">http://forums.matronics.com
p://www.matronics.com/contribution">http://www.matronics.com/contribution


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Bill1200



Joined: 19 Oct 2008
Posts: 111
Location: medford oregon

PostPosted: Wed Sep 07, 2011 4:14 pm    Post subject: Re: Low Emergency Air Pressure Reply with quote

Thanks to all for the great suggestions.
Dennis, I filled it externally and sprayed soapy water... no leak at the fill port. Watched it for over an hour, bled the brakes as you suggested, no "woosh", and no drop on the guages during that time either. I won't be able to check it again until Friday. The leak detector sounds like a must have with these beast, so it is on the way also. Thanks again.


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PostPosted: Wed Sep 07, 2011 4:29 pm    Post subject: Low Emergency Air Pressure Reply with quote

My CJ-6 was born without up locks. I just need to keep the gear handle up else the gear will eventually fall down without any air pressure - if I happen to turn off the air tank or lose the compressor. I like it like that. Few points of failure.

Speaking there of - I removed the instructor's cut out valve on the rear control stick. I removed all the hoses and pipes from the QS1 to the QS2 and simply run a tube directly from one to the another. That could have been at least 6 points failure/leaks.

One thing that has also helped me, is going to stainless steel parts when I can find them. Springs especially.

Jim "Pappy" Goolsby

In a message dated 9/7/2011 1:08:01 P.M. Eastern Daylight Time, brian(at)lloyd.com writes:
Quote:


On Wed, Sep 7, 2011 at 9:35 AM, Yak Pilot <yakplt(at)yahoo.com (yakplt(at)yahoo.com)> wrote:
Quote:
Brian, I am not sure how you could away with any of these check valves and keep system isolation. You have two input air sources, and you have two bottles. Each air input needs to be isolated from each other and each bottle needs to be isolated from each other. How could you get away with less?


Maybe you need to look at the CJ6A pneumatic system, which is what I was dealing with when troubleshooting and making my observations.


The problem is, while the check valves ostensibly provide isolation, they don't really because there really is only a single source of pressure in the entire system. So a failure in any subsystem results in depressurization of the entire system. Yes, it is possible that, if you already have the gear down some of those check-valves might hold the pressure in the down-circuit there is no separate storage in the gear circuit to allow you to still put the gear down. So the backup/emergency system really is the only solution, thus making almost all the check-valves in main system superfluous.


You can repeat my thought experiment. Take the pneumatic system schematic, imagine system breaches at different points, and then see what the effect is on the rest of the system. Now repeat the process while removing various check valves from the schematic. I think you will find that in VERY few cases do the check valves allow the rest of the system to continue to work. The only real answer is the emergency system.


OTOH, I also got see how check valves fail. If not properly maintained (and a lot of them are not properly maintained) the carbon-steel springs corrode, fail, and spread pieces of rust through the system. The funny thing is, even with the failed check valves, the system operates normally, except when the rust gets into things like valves and actuators. Wink


Now it has been awhile since I looked at the schematic for the Yak-52 pneumatic system so perhaps my points are less valid for that system.


But never underestimate the power of KISS. Remember, when something isn't there it can't fail.

--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)

Quote:


="http://www.matronics.com/Navigator?Yak-List">http://www.matronics.com/Navigator?Yak-List
s.matronics.com/">http://forums.matronics.com
p://www.matronics.com/contribution">http://www.matronics.com/contribution


[quote][b]


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Rob Rowe



Joined: 10 Jan 2006
Posts: 124
Location: Berkshire, UK

PostPosted: Wed Sep 07, 2011 5:55 pm    Post subject: Re: Low Emergency Air Pressure Reply with quote

Hi Brian

Quote:

Skip this next bit if you're easily bored ;-)

No worries. I love the details.


Me too.

Quote:

Air charging NRVs:
Main - failure dumps main system pressure overboard [essential]
Reserve - ditto for emergency air [essential]
Compressor (feeds main) - failure dumps system pressure on opening snot valve [highly desirable!]

Protection Valve - needed to EASILY depressurise emergency system after use (you could just keep pumping the brakes though) & stop seepage operating emergency gear systems [highly desirable]

Are you talking about a check valve or the shuttle valve that is used to automatically select system source (main or emergency)?


NRV = check valve

Protection valve = specialist in-line device that vents both sides to atmosphere below line pressure of 5 kgf/cm2

Quote:

In many cases the problem is not one of preventing flow back into an upstream [sub]system that has failed but that forward flow into a failed subsystem still drains the source, making the overall pneumatic systems unusable.


This is also true

Quote:

But you may find that two or more of these valves that you have listed as essential, can have their functions fulfilled by a single, strategically-place check valve.


Possibly ... just not probably in this case. The -52 approach appears to have been to use as few check valves as possible & place them such that their likely serviceability is brought to your attention during a pre-flight inspection.

IMHO I prefer this -52 design as while it may make any in-flight failure of greater consequence, it is at least in terms of largely black & white remedial actions. Rather than the shades of grey that may result from systems designed with numerous embedded check valves whose serviceability is largely indeterminate until something fails else where.

Guess this is where we came in ;-)

Brgds, Rob R


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brian(at)lloyd.com
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PostPosted: Wed Sep 07, 2011 7:38 pm    Post subject: Low Emergency Air Pressure Reply with quote

On Wed, Sep 7, 2011 at 6:55 PM, Rob Rowe <yak-list(at)robrowe.plus.com (yak-list(at)robrowe.plus.com)> wrote:
Quote:
> Are you talking about a check valve or the shuttle valve that is used to automatically select system source (main or emergency)?
>


NRV = check valve

Protection valve = specialist in-line device that vents both sides to atmosphere below line pressure of 5 kgf/cm2


I don't recall any of those on the CJ6A.�
Quote:

> In many cases the problem is not one of preventing flow back into an upstream [sub]system that has failed but that forward flow into a failed subsystem still drains the source, making the overall pneumatic systems unusable.
>


This is also true


>
> But you may find that two or more of these valves that you have listed as essential, can have their functions fulfilled by a single, strategically-place check valve.
>


Possibly ... just not probably in this case. The -52 approach appears to have been to use as few check valves as possible & place them such that their likely serviceability is brought to your attention during a pre-flight inspection.


That does seem to be different than the CJ6A�
Quote:

IMHO I prefer this -52 design as while it may make any in-flight failure of greater consequence, it is at least in terms of largely black & white remedial actions. Rather than the shades of grey that may result from systems designed with numerous embedded check valves whose serviceability is largely indeterminate until something fails else where.


I agree completely.�
Quote:

Guess this is where we came in Wink


�Indeed it is. Smile

--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)

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