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Bill1200

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

Posted: Mon Jun 23, 2014 11:15 am Post subject: Pressure Problem

Yak 52

Noticed on recent flight, pressure would not go above about 2.5. Filled it externally to pop off around 5 after landing. Checked it a several days later, it had bled down to about 4.5, not unusual for this plane. Took it out to the ramp, actuated flaps until it decreased to about 3, revved it up and watched pressure build.  Next flight no problem. Following flight same issue, wouldn't build pressure. Checked for leaks in cockpit with U/S detector, none found. Stumped, any suggestions welcome,thanks.

dsavarese0812(at)bellsout
Guest

Posted: Mon Jun 23, 2014 4:27 pm Post subject: Pressure Problem

When was the last         time you removed the snot bottle and           flushed it out thoroughly through all three orifices (in, out                 and drain).  Try that first.  I                   think you'll be quite surprised                     at how gunked up the snot bottle can get.

                     Dennis

                           	  Quote: 	
		  A. Dennis Savarese

334-285-6263

334-546-8182 (mobile)

www.yak-52.com

Skype - Yakguy1 	
       On 6/23/2014 2:15 PM, Bill1200 wrote:

     

     [quote]        	  Quote: 	
		  --> Yak-List message posted by: "Bill1200" <billdykes52(at)hotmail.com> (billdykes52(at)hotmail.com)



Yak 52

Noticed on recent flight, pressure would not go above about 2.5. Filled it externally to pop off around 5 after landing. Checked it a several days later, it had bled down to about 4.5, not unusual for this plane. Took it out to the ramp, actuated flaps until it decreased to about 3, revved it up and watched pressure build.  Went for flight with starting pressure around 3, never got higher than that during flight. Used U/S detector in both cockpits, around fittings, brakes, etc no leak detected. Stumped, any suggestions welcome, thanks.





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=425342#425342



	
     [b]

Bill1200

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

Posted: Mon Jun 23, 2014 4:54 pm Post subject: Re: Pressure Problem

Thanks Dennis, I'm looking at the pneumatic schematic (trying to understand it), if it was the snot valve staying open, wouldn't it bleed down fairly quickly when parked?

Bill1200

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

Posted: Mon Jun 23, 2014 5:02 pm Post subject: Re: Pressure Problem

BTW Dennis, forgot to answer your question. Just bought this plane so no idea if or when that was done.

Rob Rowe

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

Posted: Tue Jun 24, 2014 4:03 am Post subject: Re: Pressure Problem

Few additional thoughts to add to Dennis's sage advice on some areas worth exploring next time it fails to charge up when airborne.



Assumptions - the flap actuators are probably leak free as you've successfully cycled these on ground runs & the system has charged OK afterward.



Next airborne occurrence move gear selector to neutral to isolate gear system (don't forget to cycle back to 'Up' before subsequently selecting 'Down' to land as otherwise no back pressure to cushion operation and gear will deploy with a bang!). 



1 - if the pressure improves in neutral then you possibly have an (intermittent) leak downstream in the gear (up) system - hence why this doesn't manifest itself on the ground. Favourite here for an intermittent problem would be the front gear selector itself. With a GIB you could try selecting gear Up again using rear cockpit selector (isolates the front selector), if pressure improves then overhaul front selector. Failing that then little option but to put the aircraft on jacks and ground cycle gear till it happens again to fault find i.e. the leak is keeping pace with the compressor output so the main air system doesn't charge. 



2 - if the pressure doesn't improve in neutral this may suggest the pressure regulation valve (PRV) on the firewall has a problem. Get it cleaned / overhauled and adjusted. There could be other devices causing a problem (as Dennis suggests) but FWIW in my experience the PRV is often the culprit



YMMV - I had a long term intermittent air problem many years back that only occurred airborne, that turned out to be a defect in the PRV itself that required replacement (even after being overhauled). It would intermittently stick open venting to atmosphere after the gear was selected down ... downstream pressure drop triggered it presumably. Until the main air pressure fell to around 20kgf/cm2, then it would snap shut again and the system would recharge ok. Fine for a few flights then it would happen again! Had no re-occurrence in nearly 10 years since PRV replaced. 



Hope this helps.



Brgds, Rob R.

dsavarese0812(at)bellsout
Guest

Posted: Tue Jun 24, 2014 4:04 am Post subject: Pressure Problem

Yes, it would bleed down quickly.  But if it is staying closed and you are not pressuring the main air tank with the engine running, it COULD be a gunked up snot bottle.

Dennis

        From: Bill1200  <billdykes52(at)hotmail.com>

 To: yak-list(at)matronics.com 

 Sent: Monday, June 23, 2014 7:54 PM

 Subject: Re: Pressure Problem

--> Yak-List message posted by: "Bill1200" <billdykes52(at)hotmail.com (billdykes52(at)hotmail.com)>

Thanks Dennis, I'm looking at the pneumatic schematic (trying to understand it), if it was the snot valve staying open, wouldn't it bleed down fairly quickly when parked?

Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=425346#425========================http://www.matronics.com/Navigator?Yak-List<;  [quote][b]

mark.bitterlich(at)navy.m
Guest

Posted: Tue Jun 24, 2014 5:55 am Post subject: Pressure Problem

Just some additional musings.



What I am reading here is that the aircraft was filled externally on the deck.  The aircraft held (more or less) pressure on the deck.



On startup and taxi, air was used and it built back up normally, which tends to eliminate leaks at that exact moment of time.



After take-off, pressure would not build.



I'd suggest you might want to consider jacking the plane, putting the gear UP and checking to see that you do not have an leak with the gear UP and not DOWN.     It is entirely possible for that to happen and your description is pretty much pointing to it.



Mark





--

Bill1200

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

Posted: Tue Jun 24, 2014 10:40 am Post subject: Re: Pressure Problem

Thanks to all. Good stuff and something I can do. 

Is the PRV the same as the "pop/off" ???

KingCJ6(at)aol.com
Guest

Posted: Tue Jun 24, 2014 10:51 am Post subject: Pressure Problem

Pressure Relief Valve

  

  In a message dated 6/24/2014 11:43:30 A.M. Pacific Daylight Time,  billdykes52(at)hotmail.com writes:

  	  Quote: 	
		  -->    Yak-List message posted by: "Bill1200"    <billdykes52(at)hotmail.com>



Thanks to all. Good stuff and something    I can do. 

Is the PRV the same as the "pop/off" ???





Read    this topic online    here:



http://forums.matronics.com/viewtopic.php?p=425377#425377

	


 [quote][b]

dsavarese0812(at)bellsout
Guest

Posted: Tue Jun 24, 2014 10:52 am Post subject: Pressure Problem

Yes.

               	  Quote: 	
		  A. Dennis Savarese

334-285-6263

334-546-8182 (mobile)

www.yak-52.com

Skype - Yakguy1 	
       On 6/24/2014 1:40 PM, Bill1200 wrote:

     

     [quote]        	  Quote: 	
		  --> Yak-List message posted by: "Bill1200" <billdykes52(at)hotmail.com> (billdykes52(at)hotmail.com)



Thanks to all. Good stuff and something I can do. 

Is the PRV the same as the "pop/off" ???





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=425377#425377



	
     [b]

Viperdoc

Joined: 19 Apr 2014
Posts: 484
Location: 08A

Posted: Tue Jun 24, 2014 12:05 pm Post subject: Pressure Problem

Yes.

Doc



Sent from my iPad



 	  Quote: 	
		   On Jun 24, 2014, at 1:40 PM, Bill1200 <billdykes52(at)hotmail.com> wrote:

 

 

 

 Thanks to all. Good stuff and something I can do. 

 Is the PRV the same as the "pop/off" ???

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=425377#425377

_________________
Viperdoc

picko

Joined: 20 Nov 2013
Posts: 13

Posted: Tue Jun 24, 2014 3:24 pm Post subject: Pressure Problem

When airborne leave the gear selector in neutral after gear up. If your pressure rises you know you have and actuator leak in the up mode.



Sent from Alspad.



On 24 Jun 2014, at 8:29 am, "A. Dennis Savarese" <dsavarese0812(at)bellsouth.net (dsavarese0812(at)bellsouth.net)> wrote:

[quote]                   When was the last         time you removed the snot bottle and           flushed it out thoroughly through all three orifices (in, out                 and drain).  Try that first.  I                   think you'll be quite surprised                     at how gunked up the snot bottle can get.

                     Dennis

                           	  Quote: 	
		  A. Dennis Savarese

334-285-6263

334-546-8182 (mobile)

www.yak-52.com

Skype - Yakguy1 	
       On 6/23/2014 2:15 PM, Bill1200 wrote:

     

      	  Quote: 	
		          	  Quote: 	
		  --> Yak-List message posted by: "Bill1200" <billdykes52(at)hotmail.com> (billdykes52(at)hotmail.com)



Yak 52

Noticed on recent flight, pressure would not go above about 2.5. Filled it externally to pop off around 5 after landing. Checked it a several days later, it had bled down to about 4.5, not unusual for this plane. Took it out to the ramp, actuated flaps until it decreased to about 3, revved it up and watched pressure build.  Went for flight with starting pressure around 3, never got higher than that during flight. Used U/S detector in both cockpits, around fittings, brakes, etc no leak detected. Stumped, any suggestions welcome, thanks.





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=425342#425342



	
     

	


[b]

dsavarese0812(at)bellsout
Guest

Posted: Wed Jun 25, 2014 4:19 am Post subject: Pressure Problem

MOST IMPORTANTLY - If you do this test as Al suggested, be certain to put the gear selector back into the UP position BEFORE you put the gear down.  Putting it back in the UP posistion repressurizes the actuators.  If you don't do this and put the gear selector DOWN from the neutral position, the gear will slam into the down position just like when you extend the gear with the emergency air system.  It WILL get your attention.



Dennis



        From: Al Pickering <alpick(at)live.com.au>

 To: "yak-list(at)matronics.com" <yak-list(at)matronics.com> 

 Sent: Tuesday, June 24, 2014 6:23 PM

 Subject: Re: Pressure Problem

  

 

When airborne leave the gear selector in neutral after gear up. If your pressure rises you know you have and actuator leak in the up mode.



Sent from Alspad.



On 24 Jun 2014, at 8:29 am, "A. Dennis Savarese" <dsavarese0812(at)bellsouth.net (dsavarese0812(at)bellsouth.net)> wrote:

[quote]                   When was the last         time you removed the snot bottle and           flushed it out thoroughly through all three orifices (in, out                 and drain).  Try that first.  I                   think you'll be quite surprised                     at how gunked up the snot bottle can get.

                     Dennis

                           	  Quote: 	
		  A. Dennis Savarese

334-285-6263

334-546-8182 (mobile)

www.yak-52.com

Skype - Yakguy1 	
       On 6/23/2014 2:15 PM, Bill1200 wrote:

     

      	  Quote: 	
		          	  Quote: 	
		  --> Yak-List message posted by: "Bill1200" <billdykes52(at)hotmail.com> (billdykes52(at)hotmail.com)


Yak 52

Noticed on recent flight, pressure would not go above about 2.5. Filled it externally to pop off around 5 after landing. Checked it a several days later, it had bled down to about 4.5, not unusual for this plane. Took it out to the ramp, actuated flaps until it decreased to about 3, revved it up and watched pressure build.  Went for flight with starting pressure around 3, never got higher than that during flight. Used U/S detector in both cockpits, around fittings, brakes, etc no leak detected. Stumped, any suggestions welcome, thanks.





Read this topic online here:


http://forums.matronics.com/viewtopic.php?p=425342#425342












	
     



	


http://www.matronics.com/cont3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D


[b]

keithmckinley

Joined: 11 Aug 2008
Posts: 434

Posted: Wed Jun 25, 2014 5:29 am Post subject: Re: Pressure Problem

The gear and flap selector valve has a small port that will vent air when the selector is moved from one position to the other. I've had one of these selector valves leak so bad through this port I could not build full pressure. 

If you have started playing with the ones in the rear cockpit you may start there.  



Mine was a CJ and I believe the selectors are the same in a Yak

dsavarese0812(at)bellsout
Guest

Posted: Wed Jun 25, 2014 5:39 am Post subject: Pressure Problem

Yes, they are the same and 100% interchangeable.  If you intend to R&R a gear or flap selector, (the flap selectors and front gear selector are the same), be very careful removing the fittings because they are quite scarce.  You can easily gall the pipe threads trying to remove the old ones if you don't heat them up sufficiently before removing them.

Dennis

        From: keithmckinley <cetopfed(at)gmail.com>

 To: yak-list(at)matronics.com 

 Sent: Wednesday, June 25, 2014 8:29 AM

 Subject: Re: Pressure Problem

--> Yak-List message posted by: "keithmckinley" <cetopfed(at)gmail.com (cetopfed(at)gmail.com)>

The gear and flap selector valve has a small port that will vent air when the selector is moved from one position to the other. I've had one of these selector valves leak so bad through this port I could not build full pressure. 

If you have started playing with the ones in  the rear cockpit you may start there.  

Mine was a CJ and I believe the selectors are the same in a Yak

--------

Keith McKinley

700HS

X26 Sebastian, FL

Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=425avigator?Yak-List" "http://forums.matronics.com/" target="_blank">http://forums.matronics.cosp;                     -nics.com/contribution" target="_blank">http://www.matronics.com/contribut===============

 [quote][b]

mark.bitterlich(at)navy.m
Guest

Posted: Wed Jun 25, 2014 6:47 am Post subject: Pressure Problem

Absolutely correct, and I forgot about that!   It's also a good trick to know from the aspect of safety.    I flew a YAK-50 out to the west coast one time that had a major leak in when the gear was lowered.   Putting the gear handle in the middle after putting the gear down allowed pressure to build back up before landing allowing enough air for brakes etc.   Not sure if you would want to try that same trick in a 52 since the gear locking mechanism is totally different.



However, darn good point Al, and something not many know.



Mark

--

mark.bitterlich(at)navy.m
Guest

Posted: Wed Jun 25, 2014 8:11 am Post subject: Pressure Problem

Actually Keith, the gear selector in the YAK is something you really need to know in detail.   When I first got my 50, I noticed that the gear handle "had a leak".   I removed it from the aircraft, took it all apart, and there was not a darn thing wrong with it.  This was about 14 years ago.



I reverse engineered every single air-line in that darn thing and finally figured it out, which it today pretty much common knowledge.



You're right about the port but it is important to know that the air you hear venting is coming from the OPPOSITE SIDE of the actuators that you are trying to pressurize.  In other words, picture this:  If you have an actuator and push on it in one direction, the internal plunger is going to push air OUT the other side!   And that air has to go SOMEPLACE and that "someplace" is out the vent you are talking about.



So when you put the gear handle DOWN, air goes in and forces the actuators to move.  The air on the OPPOSITE side of that piston is then pushed out of the actuator, up through the air lines, to the gear actuator and out the vent.



An important things to realize about this.



The actuators are internally sealed (in the YAK-50) with rubber Chevron Seals.   These can fail, meaning they will leak.   This is of course a very bad thing and needs to be corrected immediately.   How do you know it is happening?  Because when the gear goes down (or up) and the handle is left in that position, air pressure is constantly fed to the piston in the actuator.  If the internal seals leak, the air will come out the opposite side of the actuator, go up the air-lines to the gear actuator handle and HISS out of the vent port constantly.   This can leak you to believe you have a bad gear actuator selector when in fact you have a serious problem in your gear actuator(s)!



So bottom line, if you hear air hissing out of the gear actuator lever in the cockpit, do not immediately assume there is a leak in the gear selector, instead check to see if it is coming out of the VENT in which case, suspect a leaking gear actuator seal.



Mark



--

Ernie

Joined: 11 Jan 2006
Posts: 513

Posted: Wed Jun 25, 2014 8:55 am Post subject: Pressure Problem

Why then does the gear slam down if the selector is left in neutral?



Ernie



On Wed, Jun 25, 2014 at 12:48 PM, doug sapp <dougsappllc(at)gmail.com (dougsappllc(at)gmail.com)> wrote:

 [quote]Mark,Great post and explanation of how the system works, much better than I could have done myself. Â 100% spot on.

 



Doug



 On Wed, Jun 25, 2014 at 9:10 AM, Bitterlich, Mark G CIV NAVAIR, WD <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)> wrote:

[quote]  --> Yak-List message posted by: "Bitterlich, Mark G CIV NAVAIR, WD" <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>

 

 Actually Keith, the gear selector in the YAK is something you really need to know in detail. Â  When I first got my 50, I noticed that the gear handle "had a leak". Â  I removed it from the aircraft, took it all apart, and there was not a darn thing wrong with it. Â This was about 14 years ago.

   

 I reverse engineered every single air-line in that darn thing and finally figured it out, which it today pretty much common knowledge.

 

 You're right about the port but it is important to know that the air you hear venting is coming from the OPPOSITE SIDE of the actuators that you are trying to pressurize. Â In other words, picture this: Â If you have an actuator and push on it in one direction, the internal plunger is going to push air OUT the other side! Â  And that air has to go SOMEPLACE and that "someplace" is out the vent you are talking about.

   

 So when you put the gear handle DOWN, air goes in and forces the actuators to move. Â The air on the OPPOSITE side of that piston is then pushed out of the actuator, up through the air lines, to the gear actuator and out the vent.

   

 An important things to realize about this.

 

 The actuators are internally sealed (in the YAK-50) with rubber Chevron Seals. Â  These can fail, meaning they will leak. Â  This is of course a very bad thing and needs to be corrected immediately. Â  How do you know it is happening? Â Because when the gear goes down (or up) and the handle is left in that position, air pressure is constantly fed to the piston in the actuator. Â If the internal seals leak, the air will come out the opposite side of the actuator, go up the air-lines to the gear actuator handle and HISS out of the vent port constantly. Â  This can leak you to believe you have a bad gear actuator selector when in fact you have a serious problem in your gear actuator(s)!

   

 So bottom line, if you hear air hissing out of the gear actuator lever in the cockpit, do not immediately assume there is a leak in the gear selector, instead check to see if it is coming out of the VENT in which case, suspect a leaking gear actuator seal.

   

 Mark

 

 

 

 --

mark.bitterlich(at)navy.m
Guest

Posted: Wed Jun 25, 2014 10:35 am Post subject: Pressure Problem

Dennis pretty much explained this, but the reason is that if you put the gear handle in the middle, all pressure is released on BOTH sides of the actuator.   The actuator then is at standard atmospheric.



When the gear is then selected to go DOWN, the piston does not have to push compressed air out the OTHER side to the vent in the gear handle.  Thus there is no resistance at all when 735 PSI of air is applied to the down side.



Think of it this way.... when you normally select DOWN on the gear handle, you previously had it in the UP position.  When it is UP, there is 735 PSI on the actuator pushing on the UP side.



When you select DOWN, pressure is applied to the other side, but the air is still in there on the UP side and has to be vented out of the small hole in the gear handle itself.  This acts like a buffer... as the gear goes down, the speed it goes down is partially controlled by how fast you can vent the air out of the UP side of the piston, thus this slows down the gear extension.



If you put the handle in the MIDDLE, all the air is vented out.....  UP, DOWN, all of it... vented.



Now when you select DOWN, there is no air cushion to vent out from the UP  side, and the gear is put down with the full force of the 735 PSI of air on the down side and it just SLAMS DOWN HARD.  Not a good thing.



Not my best explanation, but hope you can understand.



Mark

--

cjpilot710(at)aol.com
Guest

Posted: Wed Jun 25, 2014 11:05 am Post subject: Pressure Problem

Here is one more thing to add.  Some CJs come WITH OUT up locks.   Normally when you put the gear handle in the middle which lets pressure off both  sides of the piston in the actuator, the gear is held up by the spring  loaded 'up locks' otherwise they would fall down.  When you put the gear  handle down, not only do you pressurized the down side of the actuator -  you also unlock the up locks - normally.  However as I said some CJ  (mine in particular) came WITHOUT up locks.  As a result I need to fly  with my gear handle ALWAY in the up position, otherwise they fall  down.  If I hear air coming from the gear handle, while the gear  handle it self could leak, more than likely its one the 3 actuators that might  be leaking.

  

 My system is simpler in that the line to the up locks are capped off.   If I lose air pressure (bad leak or compressor shear its pins), my gear simply  falls down thanks to gravity.  BUT they don't lock over center down, and  that's when I need to use the emergency air pressure.  I simply put the  handle down and open the emergency air valve.  Over the 20 years I've own  my CJ this has happen twice.  Both times was because of a compressor  failure of kind or another.

  

 Jim "Pappy" Goolsby

  

  

  In a message dated 6/25/2014 2:35:47 P.M. Eastern Daylight Time,  mark.bitterlich(at)navy.mil writes:

 [quote]-->    Yak-List message posted by: "Bitterlich, Mark G CIV NAVAIR, WD"    <mark.bitterlich(at)navy.mil>



Dennis pretty much explained this, but    the reason is that if you put the gear handle in the middle, all pressure is    released on BOTH sides of the actuator.   The actuator then is at    standard atmospheric.



When the gear is then selected to go DOWN, the    piston does not have to push compressed air out the OTHER side to the vent in    the gear handle.  Thus there is no resistance at all when 735 PSI of air    is applied to the down side.



Think of it this way.... when you normally    select DOWN on the gear handle, you previously had it in the UP    position.  When it is UP, there is 735 PSI on the actuator pushing on the    UP side.



When you select DOWN, pressure is applied to the other side,    but the air is still in there on the UP side and has to be vented out of the    small hole in the gear handle itself.  This acts like a buffer... as the    gear goes down, the speed it goes down is partially controlled by how fast you    can vent the air out of the UP side of the piston, thus this slows down the    gear extension.



If you put the handle in the MIDDLE, all the air is    vented out.....  UP, DOWN, all of it... vented.



Now when you    select DOWN, there is no air cushion to vent out from the UP  side, and    the gear is put down with the full force of the 735 PSI of air on the down    side and it just SLAMS DOWN HARD.  Not a good thing.



Not my best    explanation, but hope you can understand.



Mark

-----Original    Message-----

From: owner-yak-list-server(at)matronics.com    [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Ernest    Martinez

Sent: Wednesday, June 25, 2014 12:55 PM

To:    yak-list

Subject: Re: Re: Pressure Problem



Why then does    the gear slam down if the selector is left in    neutral?



Ernie

On Wed, Jun 25, 2014 at 12:48 PM, doug sapp    <dougsappllc(at)gmail.com> wrote:

           Mark,

        Great post and explanation of how the    system works, much better than I could have done myself.  100% spot    on.



        Doug

           On Wed, Jun 25, 2014 at 9:10 AM, Bitterlich, Mark G CIV NAVAIR, WD    <mark.bitterlich(at)navy.mil> wrote:

                   --> Yak-List message posted by: "Bitterlich,    Mark G CIV NAVAIR, WD" <mark.bitterlich(at)navy.mil>



                   Actually Keith, the gear selector in    the YAK is something you really need to know in detail.   When I    first got my 50, I noticed that the gear handle "had a leak".   I    removed it from the aircraft, took it all apart, and there was not a darn    thing wrong with it.  This was about 14 years ago.



                   I reverse engineered every single    air-line in that darn thing and finally figured it out, which it today pretty    much common knowledge.



                   You're right about the port but it is important to know that the air    you hear venting is coming from the OPPOSITE SIDE of the actuators that you    are trying to pressurize.  In other words, picture this:  If you    have an actuator and push on it in one direction, the internal plunger is    going to push air OUT the other side!   And that air has to go    SOMEPLACE and that "someplace" is out the vent you are talking    about.



                So when    you put the gear handle DOWN, air goes in and forces the actuators to    move.  The air on the OPPOSITE side of that piston is then pushed out of    the actuator, up through the air lines, to the gear actuator and out the    vent.



                An    important things to realize about this.



                   The actuators are internally sealed (in the    YAK-50) with rubber Chevron Seals.   These can fail, meaning they    will leak.   This is of course a very bad thing and needs to be    corrected immediately.   How do you know it is happening?     Because when the gear goes down (or up) and the handle is left in that    position, air pressure is constantly fed to the piston in the actuator.     If the internal seals leak, the air will come out the opposite side of the    actuator, go up the air-lines to the gear actuator handle and HISS out of the    vent port constantly.   This can leak you to believe you have a bad    gear actuator selector when in fact you have a serious problem in your gear    actuator(s)!



                So    bottom line, if you hear air hissing out of the gear actuator lever in the    cockpit, do not immediately assume there is a leak in the gear selector,    instead check to see if it is coming out of the VENT in which case, suspect a    leaking gear actuator seal.



                   Mark



                   --

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