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Compressor Conundrum

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HawkerPilot2015

Joined: 10 Jan 2006
Posts: 503

Posted: Sat Nov 25, 2006 8:21 pm Post subject: Compressor Conundrum

So I am all proud of myself and get the compressor switched out with an overhauled one. I run the airplane up and it "seems" the compressor is working...or maybe exitement to be flying again got the best of me. I take her airborne and as I cycle the gear, it comes up really slowly. I bunt the airplane and get two up locks (Yak-50). I trouble shoot the problem and discover once again I am not making air and my primary side is gone! (The compressor on the -50 charges both sides) Time to test the emer gear down and land without incident...or brakes. All is well with the airplane and me. 



So.....here is what I know (or think I know);



-The overhauled compressor and shear coupling were both operational when they were installed in the airplane. 

-The check valve from the compressor to the line running to the snot valve was clean and free moving. 

-I cleaned out the snot valve before reinstalling. 



- I am not making air indicated by the fact that there is no rise in air pressure OR and air in the snot valve after a lengthy runup. 



SO I ASK...WTF! 



A few things I have tried:



I did the following while motoring the engine:



*Had someone keep their finger over the "output" end of the air line running from the compressor to snot valve. Nothing noted.



* Took that line off and held finger over output on check valve attached to the compressor. Nothing noted. (Now I am getting nervous.)



* Took the check valve off the compressor and kept finger over small orfice that check valves screws into and finally get some air. 



* Put small surgical glove over intake on compressor and found that indeed the compressor collapsed the glove which means that the coupling is still working and driving the piston in the compressor. (Big relief..hopefully)



* The line runnning from the compressor to the snot valve is clear. I used shop air to confirm that. 



So that leaves me with some serious question about what the problem could be.



1.) Is there a certain power setting that needs to be achieved before the check valve "opens"?

2.) Is the check valve not working?

3.) Is there something inside the gearbox that is not "spinning" fast enough to provide enough power to the compressor itself?



4.) Will .40 cal hollow points penetrate the crankcase on an M-14P?



I thought I narrowed the problem down but I am really confused on what it could be. 



I REALLY dont want to take the compressor back off. I would rather drink 100LL and piss on a fire.



$100.00 to the first person who comes up with the right solution.

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jan.mevis(at)informavia.b
Guest

Posted: Sun Nov 26, 2006 2:05 am Post subject: Compressor Conundrum

Did you really check all the small tubes and connectors in the main air

circuit? I recently lost all pressure in the main circuit of my Yak 50 after

doing some touch and go's and I first also thought that the compressor was

not working, but after landing (with the emergency system) and a few hours

work (using soap the way plumbers do it) I found a small tube broken just

behind the screw that tightens it. It seems that those aluminum tubes get

brittle after some time. So I replaced it with an iron tube. 



Jan Mevis

Yak 50 RA2005K



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dsavarese(at)elmore.rr.co
Guest

Posted: Sun Nov 26, 2006 5:50 am Post subject: Compressor Conundrum

Tim,

Since you found out you were making air at the compressor and not making air 

at the output of the check valve, two things immediately come to mind.  The 

crush washers on the output check valve (I believe there are 4) are leaking 

or at least one of them is; the small valve that is suppose to be able to 

move up and down (there's a spring inside the little valve) is sticking or 

stuck.  There is always the possibility the overhauled compressor second 

stage is the problem in which case you won't build up high pressure.

Dennis



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HawkerPilot2015

Joined: 10 Jan 2006
Posts: 503

Posted: Sun Nov 26, 2006 5:54 am Post subject: Re: Compressor Conundrum

 	  jan.mevis(at)informavia.b wrote: 	
		  Did you really check all the small tubes and connectors in the main air

circuit? I recently lost all pressure in the main circuit of my Yak 50 after

doing some touch and go's and I first also thought that the compressor was

not working, but after landing (with the emergency system) and a few hours

work (using soap the way plumbers do it) I found a small tube broken just

behind the screw that tightens it. It seems that those aluminum tubes get

brittle after some time. So I replaced it with an iron tube. 



Jan Mevis

Yak 50 RA2005K-- 	




I would assume that if there is no air getting to the snot bottle, checking for leaks down stream would be futile. There is something wrong between the engine and the snot bottle....my guess at least. 



Thanks for the input though.

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dsavarese(at)elmore.rr.co
Guest

Posted: Sun Nov 26, 2006 6:00 am Post subject: Compressor Conundrum

BTW, you can have Doug Sapp fabricate a new, flexible line from the banjo 

fitting on the output check valve to the input of the snot bottle if you 

think that line might have a small pin hole in it (not uncommon).  All you 

have to do is send Doug the line and he'll make up the correct length 

flexible line.

Dennis



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LawnDart

Joined: 05 Jun 2006
Posts: 64

Posted: Sun Nov 26, 2006 7:54 am Post subject: Re: Compressor Conundrum

A friend of mine had the same problem.  Mechanic installed new compressor etc - still not making air.  I was sent to troubleshoot.  Discovered the check-valve on the compressor was assembled/installed incorrectly (parts out of order and some missing).  Installed a new valve and it worked fine.



Cheers

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dsavarese(at)elmore.rr.co
Guest

Posted: Sun Nov 26, 2006 8:02 am Post subject: Compressor Conundrum

Your point is quite valid inasmuch as I have seen the small spring either 

left out during reassembly or broken, thus making the spring ineffective for 

the little valve inside the check valve.

Dennis



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HawkerPilot2015

Joined: 10 Jan 2006
Posts: 503

Posted: Sun Nov 26, 2006 5:51 pm Post subject: Re: Compressor Conundrum

I will file this in the "not sure what happened but I will take it" folder.



I took the check valve, snot valve, and the line that runs between them off the airplane this morning. I started at the compressor itself and again, found it was working. I took the check valve and ran some shop air through it and a little tool oil. Put it back on, attached a surgical glove on it and cranked the engine which exploded the glove...the pump and valve are working. Attached the line to the valve, connected it to the snot valve and attached another glove to the output side of the snot valve...blew that glove too! So, I am making air and it is FINALLY getting to the snot valve. I attach everything, button her up and run her up....I AM MAKING AIR!! I give it some time, say a prayer and take off leaving the gear down. I fly around for about 5 minutes and see good pressure and pull the gear which comes up with a rewarding thump. Fly around another 30 minutes or so when I hear what can only be described as music to my ears...the pop off valve working!!!! 



I am not sure what I did or what happened..but it is working just fine and I will take it. It has been almost two months since this thing failed. The day was absolutely beautiful and I flew.....life is good.

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dsavarese(at)elmore.rr.co
Guest

Posted: Sun Nov 26, 2006 7:07 pm Post subject: Compressor Conundrum

It was most likely in the little valve in the check valve or a crush washer 

not sealing.  Glad you got it fixed.

Dennis



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