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michael(at)wikstrom.cc
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 Posted: Tue Aug 05, 2014 7:05 am Post subject: Yak18T air leak |
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Dear Yak pilots,
Is there someone who could help me identify the cause and cure for an air leak in my 18T.
Ref attached picture, I have a constant air leak at the bottom of the unit shown with an arrow.
This part is located on the left side, inside the front inspection hatch
Once I shut the ‘main air’ this leak bleeds the ‘main air’ system in about 30 min. Emergency air is not affected.
With the engine running, the compressor fills the system faster than it leaks out, so I should still be able to go flying,
But I’m not sure I should, if the leak gets worse??
A friend suggested that this unit should not normally have air pressure inside, unless the emergency air is opened, leading to
believe that the problem might be elsewhere, a leaking shuttle valve?
Thanks
Michael Wikstrom
La Colle sur Loup (06)
France
Tel : +33 607 44 40 11
email: michael(at)wikstrom.cc
Yak 18T - F-HYAC
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ssssskippy
Joined: 02 May 2010
Posts: 58
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| Posted: Tue Aug 05, 2014 7:31 am Post subject: Yak18T air leak |
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Hi
It looks like as the air valve that permit to send air from the emergency system. This valve contains a spring that can be stucked by dust and rust.
You have to remove the part, unscrew the big cap and wash the inside with glycerine and alcohol. And the problem will be solve!
By
Olivier
2014-08-05 17:03 GMT+02:00 Michael Wikstrom <michael(at)wikstrom.cc (michael(at)wikstrom.cc)>:
[quote]
Dear Yak pilots,
Is there someone who could help me identify the cause and cure for an air leak in my 18T.
Ref attached picture, I have a constant air leak at the bottom of the unit shown with an arrow.
This part is located on the left side, inside the front inspection hatch
Once I shut the ‘main air’ this leak bleeds the ‘main air’ system in about 30 min. Emergency air is not affected.
With the engine running, the compressor fills the system faster than it leaks out, so I should still be able to go flying,
But I’m not sure I should, if the leak gets worse??
A friend suggested that this unit should not normally have air pressure inside, unless the emergency air is opened, leading to
believe that the problem might be elsewhere, a leaking shuttle valve?
Thanks
Michael Wikstrom
La Colle sur Loup (06)
France
Tel : +33 607 44 40 11
email: michael(at)wikstrom.cc
Yak 18T - F-HYAC
[b]
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Rob Rowe
Joined: 10 Jan 2006
Posts: 124
Location: Berkshire, UK
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| Posted: Wed Aug 06, 2014 1:50 am Post subject: Re: Yak18T air leak |
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Michael,
Looks like it's the 562300 protection valve (#12 bleeding down valve in attached PDF schematic - machine translated from Russian so make allowances for phrasing!).
This valve vents to atmosphere below 5 bar pressure and is used primarily to bleed down the emergency air system after use.
However it's secondary function is to vent small air leaks entering the emergency system from defective seals on either the gear up-locks or the adjacent non-return valve (NRV) emergency feed to the brakes (and flaps in the case of the -18T) .
If these get large enough (>5 bar) it shuts and the pressure build up will release the up-locks and slowly blows the gear down, which tends to get your attention!
In your case it appears whatever is leaking has yet to get to 5 bar so the protection valve is just venting it to the exterior (which you can hear).
Off the top of my head the easiest way to diagnose on the ground whether it's the adjacent NRV or an up-lock seal (#13 or #22 x 2 on diagram) is to (with CAUTION) select the gear lever to neutral to vent the gear air lines.
If the leak persists then it's probably the NRV. If the leak stops then it's probably one of the up-locks and that will be more difficult to isolate other than by carefully listening to each up-lock in turn (adjacent to actuator) for air flowing through it. A stethoscope might be useful!
Hope this helps.
Rob R
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PaulW
Joined: 14 May 2013
Posts: 25
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| Posted: Wed Aug 06, 2014 8:29 am Post subject: Re: Yak18T air leak |
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Hi
I actually never check the emergency systems and or tap/valve that it will actually work in the case of an emergency.
Also never saw this in check lists.
What is the best way to do this and how often?
Will that assist in finding faults as described in this thread?
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Rob Rowe
Joined: 10 Jan 2006
Posts: 124
Location: Berkshire, UK
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| Posted: Wed Aug 06, 2014 9:09 am Post subject: Re: Yak18T air leak |
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| PaulW wrote: |
I actually never check the emergency systems and or tap/valve that it will actually work in the case of an emergency.
Also never saw this in check lists.
What is the best way to do this and how often? |
This is an annual maintenance emergency gear operation check item with the aircraft mounted on jacks.
| Quote: | | Will that assist in finding faults as described in this thread? |
Not really - the primary issue here is what's the source of the leak, not whether the protection valve will work >5 bar (secondary issue).
Rob R
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michael(at)wikstrom.cc
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| Posted: Wed Aug 06, 2014 12:59 pm Post subject: Yak18T air leak |
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Thanks for the info Rob, I can see the logic in your explanation.
I'll let you know what I find
Michael Wikstrom
La Colle sur Loup (06)
France
Tel : +33 607 44 40 11
email: michael(at)wikstrom.cc
Yak 18T - F-HYAC
Yak 3U - F-AZZV
--
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Rob Rowe
Joined: 10 Jan 2006
Posts: 124
Location: Berkshire, UK
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| Posted: Thu Aug 07, 2014 9:41 am Post subject: Re: Yak18T air leak |
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Michael,
| Quote: | | If the leak persists then it's probably the NRV. If the leak stops then it's probably one of the up-locks and that will be more difficult to isolate other than by carefully listening to each up-lock in turn (adjacent to actuator) for air flowing through it. A stethoscope might be useful! |
My bad - I omitted to add the shuttle valves (diagram item #10 x 3) as alternative failure candidates to the up-locks. Again co-located with the gear actuators so difficult to isolate.
Rob R.
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michael(at)wikstrom.cc
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| Posted: Thu Aug 07, 2014 10:47 am Post subject: Yak18T air leak |
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Rob
The leak stopped when I put the gear lever in the neutral position so now I will check the actuator shuttle valves this week end.
Thanks again
Michael
Michael Wikström
France
Tel +33 493 95 80 93
Tel +33 607 44 40 11
| Quote: | On 7 Aug 2014, at 19:41, "Rob Rowe" <yak-list(at)robrowe.plus.com> wrote:
Michael,
> If the leak persists then it's probably the NRV. If the leak stops then it's probably one of the up-locks and that will be more difficult to isolate other than by carefully listening to each up-lock in turn (adjacent to actuator) for air flowing through it. A stethoscope might be useful!
My bad - I omitted to add the shuttle valves (diagram item #10 x 3) as alternative failure candidates to the up-locks. Again co-located with the gear actuators so difficult to isolate.
Rob R.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=428162#428162
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Vic
Joined: 12 Aug 2008
Posts: 116
Location: Southern Bavaria
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| Posted: Sat Aug 09, 2014 4:03 am Post subject: Re: Yak18T air leak |
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Hi Michael,
did you do an emergency l.g. extension recently ? Yes, I also believe the rubber balls in the actuator cylinders are deformed - standard condition, see arrows in picture. You may be able to exchange them on site, if blow gun is available. I added a few photos for assistance.
Cheers
Vic
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