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YAK 50 Air/Gear problems

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aerostar6

Joined: 26 Jun 2008
Posts: 33
Location: Amersham, UK

Posted: Tue Apr 01, 2014 1:48 am Post subject: YAK 50 Air/Gear problems

Hi all. Just finishing up an annual. Had some wear problems on the right main gear which required re-bushing. Re-assembled and on trying to pressurise the air system got a major farting noise from inside the cockpit, and no pressure going to the bottles.

On investigation, the air/noise id coming from a valve low down and forward of the right rudder pedal (see pics). Local guru says it is an air pressure regulation valve that modulates air pressure to the gear actuators to stop the gear smacking down under full pressure. We pulled the valve and tried to open it up to inspect, but the thread is peened over, and we couldn't budge it even with two wrenches and a vice - not designed to be serviced I reckon.

However, in wrestling it around something inside clicked, and on a hunch we re-installed it and, hey presto it started working again. 

Q. I don't understand how this valve is placed in the system so that it stops air from the filler going direct to the bottles if it is there to damp surges to the gear - does anyone have a schematic?

Q. Does anyone have one of these valves to swap the dodgy one out?



Secondly, does anyone have any idea how much play should be seen on the legs when in the up position when on the up locks? Right gear has a couple of mm of up/down movement, whereas the left gear is held hard into the uplock with no play at all.



Thirdly, has anyone got access to a service kit for the air pressure blow-off valve? I have a broken spring and worn seal in the plunger and no suppliers in the UK.



Thanks in advance....

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aerostar6

Joined: 26 Jun 2008
Posts: 33
Location: Amersham, UK

Posted: Tue Apr 01, 2014 1:55 am Post subject: Re: YAK 50 Air/Gear problems

and photo......

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aerostar6

Joined: 26 Jun 2008
Posts: 33
Location: Amersham, UK

Posted: Tue Apr 01, 2014 1:57 am Post subject: Re: YAK 50 Air/Gear problems

and where it lives....

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Harv

Joined: 01 Jul 2010
Posts: 172

Posted: Thu Apr 03, 2014 2:13 am Post subject: Re: YAK 50 Air/Gear problems

Aerostar



Have you tried Vintage Aero at Pent Farm for that in line valve? If they don't have it in stock i bet they can get one. I believe they have now taken over operating Russian Engineering at WLAC.



With your pressure reducing valve try Doug Sapp (http://www.cj6.org).  If this part is the same as the CJ6 then he stocks a kit to service it (new piston with rubber seal on one end, spring etc...)



Rgs

Harv

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Vic

Joined: 12 Aug 2008
Posts: 115
Location: Southern Bavaria

Posted: Thu Apr 03, 2014 4:01 am Post subject: Re: YAK 50 Air/Gear problems

Hi,

that valve does no regulation at all, it is either open or closed. I think it is a sort of blow-off valve related to the emergency extension of the landing gear. If it works now, OK. See the photos below, there is a spring loaded piston that is kept closed with sufficient air pressure. The speed of the gear extension is restricted elsewhere .



   Vic

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dsavarese0812(at)bellsout
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Posted: Thu Apr 03, 2014 4:15 am Post subject: YAK 50 Air/Gear problems

You are correct Vic.  We call it the "fart" valve because that's what it sounds like when it finally opens, which is at a very few atmospheres.  

Dennis





        From: Vic <vicmolnar(at)aol.com>

 To: yak-list(at)matronics.com 

 Sent: Thursday, April 3, 2014 7:01 AM

 Subject: Re: YAK 50 Air/Gear problems

  

 

-->  Yak-List message posted by: "Vic" <vicmolnar(at)aol.com (vicmolnar(at)aol.com)>



Hi,

that valve does no regulation at all, it is either open or closed. I think it is a sort of blow-off valve related to the emergency extension of the landing gear. If it works now, OK. See the photos below, there is a spring loaded piston that is kept closed with sufficient air pressure. The speed of the gear extension is restricted elsewhere .



   Vic





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