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Air Compressor (?) Issue

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jill(at)m-14p.com
Guest

Posted: Tue Oct 15, 2013 1:15 pm Post subject: Air Compressor (?) Issue

Group,

 

We have met up with a head scratcher.  I am throwing it out to the group to chew on:

 

The Yak 52 owner purchased his aircraft on an insurance sale.  The aircraft had been totaled because of an engine fire.  Attempts to talk to the original owners and learn more about the aircraft’s history have been unsuccessful.  Originally, we were contacted because the air system was not building pressure.  A photo sent by the owner, elicited a remark by me that there seemed to be a lot of oil in the banjo/outlet valve fitting.  The compressor itself was very dirty.

The owner cleaned the outlet valve with no appreciable change in output.

He then bought a  "NOS" comp from a private party, installed it and it failed in 2.5 hours.  This compressor had actually been overhauled by us in 2006.  The nuts stripped off of the 4 studs on the bottom end of the compressor (green case), allowing the top end off the compressor to hammer up and down.  Oil was all over the back end of the engine.

 

The customer then sent his original compressor for overhaul and run on our test bench.  He installed this overhauled compressor and it failed after 40 minutes in flight. This time the 4 studs sheared off of the bottom end of the compressor.  

 

He sent us both failed compressors, the drive and drive gear, shear coupling,  the FT-1 “snot” valve and the pressure relief tee setup.  We built one compressor out of the two failed units.  The 4 stripped studs were replaced with new studs and installed with Loctite.  The compressor was test run and produced 925 psi.  The pressure relief valve tee setup was tested – it relieved normally -  rebuilt with a new piston, new seals in the one way checkvalves and the pressure set to 50 atm. (The pressure relief valve had a Teflon seal which was in very poor condition.) The snot valve was tested, flushed and retested.  The compressor, gaskets and drive unit were secured to one another in the proper alignment for the reinstall.

 

The air compressor was returned to the customer and it was reinstalled without attaching the steel air line. Everything was normal for about 1.5 hours of ground runs. 

 

A flight was completed with the steel coiled air line still not attached.  The flight was normal.

 

The steel line was reattached and 90 minutes of ground run time.  He noticed that pressure was not building as it should and opened the cowling  to find one of the 4 hold-down nuts backing off. He also reported that the other 3 nuts were not tight.  The owner drilled and safety wired the nuts.

 

(Note:  There is a CRITICAL clearance that is set between the bottom of the Stage I piston and the top of the Stage II cylinder.  Over-tightening these nuts will cause the top of the piston to hit the top of the Stage II cylinder.  Too much clearance and it bottoms out on the other end.)

 

We received the compressor and installed new studs and steel locknuts with Loctite.  The compressor has been returned but not run, yet.

 

Here is what we know:

<![if !supportLists]>1.       <![endif]>The FT-1 Snot valve is was flushed and functioning properly.

<![if !supportLists]>2.       <![endif]>The pressure relief valve tee and checkvalves were all tested and the system functioned normally on a bench test, with the pressure relief valve popping off at 750 psi. 

<![if !supportLists]>3.       <![endif]>A new steel line was provided to the customer, but I do not know if this was installed.

<![if !supportLists]>4.       <![endif]>On the 4th installation of the compressor, we returned the compressor, shear coupling, drive pad and gear tie-wrapped as a unit for correct clocking.  We received photo verification that the compressor drive was installed correctly.

<![if !supportLists]>5.       <![endif]>The compressor operated normally on the last run until the steel line was attached to it.  Then, 1 nut backed off and the other 3 were reported loose.  Hence, we replaced the hex nuts/lockwashers with steel locknuts in case the lockwashers had failed and that was the only problem on the last run.

<![if !supportLists]>6.       <![endif]>The force to shear the compressor studs is in excess of 22,000 lbs.  

<![if !supportLists]>7.       <![endif]>The shear coupling appears to be a factory unit.  A new one was sent to the customer, but returned back to me.

<![if !supportLists]>8.       <![endif]>The oil return holes in the accessory case are large and not plugged.

 

In the 20+ years that we have been overhauling air compressors, we have never encountered this problem.  Please use this problem as your own theoretical and reasoning challenge to put forth real possibilities –grasping at unicorns, rainbows or butterflies not allowed.  :  )

 

Jill

M-14P, Inc.

 

 

 

  [quote][b]

jland(at)popeandland.com
Guest

Posted: Tue Oct 15, 2013 2:23 pm Post subject: Air Compressor (?) Issue

It needs some MMO.........





On 10/15/13 5:09 PM, "Jill Gernetzke" <jill(at)m-14p.com> wrote:



Group,



We have met up with a head scratcher.  I am throwing it out to the group to chew on:



The Yak 52 owner purchased his aircraft on an insurance sale.  The aircraft had been totaled because of an engine fire.  Attempts to talk to the original owners and learn more about the aircraft's history have been unsuccessful.  Originally, we were contacted because the air system was not building pressure.  A photo sent by the owner, elicited a remark by me that there seemed to be a lot of oil in the banjo/outlet valve fitting.  The compressor itself was very dirty.

The owner cleaned the outlet valve with no appreciable change in output.

He then bought a  "NOS" comp from a private party, installed it and it failed in 2.5 hours.  This compressor had actually been overhauled by us in 2006.  The nuts stripped off of the 4 studs on the bottom end of the compressor (green case), allowing the top end off the compressor to hammer up and down.  Oil was all over the back end of the engine.



The customer then sent his original compressor for overhaul and run on our test bench.  He installed this overhauled compressor and it failed after 40 minutes in flight. This time the 4 studs sheared off of the bottom end of the compressor.



He sent us both failed compressors, the drive and drive gear, shear coupling,  the FT-1 "snot" valve and the pressure relief tee setup.  We built one compressor out of the two failed units.  The 4 stripped studs were replaced with new studs and installed with Loctite.  The compressor was test run and produced 925 psi.  The pressure relief valve tee setup was tested - it relieved normally -  rebuilt with a new piston, new seals in the one way checkvalves and the pressure set to 50 atm. (The pressure relief valve had a Teflon seal which was in very poor condition.) The snot valve was tested, flushed and retested.  The compressor, gaskets and drive unit were secured to one another in the proper alignment for the reinstall.



The air compressor was returned to the customer and it was reinstalled without attaching the steel air line. Everything was normal for about 1.5 hours of ground runs.



A flight was completed with the steel coiled air line still not attached.  The flight was normal.



The steel line was reattached and 90 minutes of ground run time.  He noticed that pressure was not building as it should and opened the cowling  to find one of the 4 hold-down nuts backing off. He also reported that the other 3 nuts were not tight.  The owner drilled and safety wired the nuts.



(Note:  There is a CRITICAL clearance that is set between the bottom of the Stage I piston and the top of the Stage II cylinder.  Over-tightening these nuts will cause the top of the piston to hit the top of the Stage II cylinder.  Too much clearance and it bottoms out on the other end.)



We received the compressor and installed new studs and steel locknuts with Loctite.  The compressor has been returned but not run, yet.



Here is what we know:

1.       The FT-1 Snot valve is was flushed and functioning properly.



2.       The pressure relief valve tee and checkvalves were all tested and the system functioned normally on a bench test, with the pressure relief valve popping off at 750 psi.



3.       A new steel line was provided to the customer, but I do not know if this was installed.



4.       On the 4th installation of the compressor, we returned the compressor, shear coupling, drive pad and gear tie-wrapped as a unit for correct clocking.  We received photo verification that the compressor drive was installed correctly.



5.       The compressor operated normally on the last run until the steel line was attached to it.  Then, 1 nut backed off and the other 3 were reported loose.  Hence, we replaced the hex nuts/lockwashers with steel locknuts in case the lockwashers had failed and that was the only problem on the last run.



6.       The force to shear the compressor studs is in excess of 22,000 lbs

pfstelwagon(at)earthlink.
Guest

Posted: Tue Oct 15, 2013 4:41 pm Post subject: Air Compressor (?) Issue

If you think about it, every time the steel line is connected  the compressor fails.  That seems to say that there is a blockage between  the compressor and the pressure relief valve.  Since compression is not  being built up in the aircraft the compressor output is blocked before the pop  off valve. Not much there the steel line the water catch bottle and the line  from there to the tee.  One other question is the compressor sensitive to  the gasket thickness between the engine and the compressor?  Why not  disconnect the compressor line and connect it to a dive bottle and see if  pressure builds up in the aircraft.  Just thinking!

  

 Frank

 [quote]   ---

viperdoc(at)mindspring.co
Guest

Posted: Tue Oct 15, 2013 6:18 pm Post subject: Air Compressor (?) Issue

One thought, since there was a fire that involved the firewall were the check valves at the pop off valve rebuilt or replaced. Is it possible that the lower check valve between the snot bottle and the pop off valve and the filter are reversed. Instead of the one way valve arrow on the check valve pointing to the filter and theophylline off valve could it be pointing at the snot bottle. Did y'all re-assemble the H or was it done in the field? Is the filter patent or is it clogged up from carbon deposited? 

I saw your #2 in the summary list that referred to testing the H setup. Was it disassemble after ya'll shipped it. As you know the check valve direction will have a big impact on air flow. 

Just a though.

Doc



Sent from my iPad



On Oct 15, 2013, at 4:09 PM, "Jill Gernetzke" <jill(at)m-14p.com (jill(at)m-14p.com)> wrote:

[quote]  <![endif]-->   <![endif]-->

Group,

 

We have met up with a head scratcher.  I am throwing it out to the group to chew on:

 

The Yak 52 owner purchased his aircraft on an insurance sale.  The aircraft had been totaled because of an engine fire.  Attempts to talk to the original owners and learn more about the aircraftâ€™s history have been unsuccessful.  Originally, we were contacted because the air system was not building pressure.  A photo sent by the owner, elicited a remark by me that there seemed to be a lot of oil in the banjo/outlet valve fitting.  The compressor itself was very dirty.

The owner cleaned the outlet valve with no appreciable change in output.

He then bought a  "NOS" comp from a private party, installed it and it failed in 2.5 hours.  This compressor had actually been overhauled by us in 2006.  The nuts stripped off of the 4 studs on the bottom end of the compressor (green case), allowing the top end off the compressor to hammer up and down.  Oil was all over the back end of the engine.

 

The customer then sent his original compressor for overhaul and run on our test bench.  He installed this overhauled compressor and it failed after 40 minutes in flight. This time the 4 studs sheared off of the bottom end of the compressor.  

 

He sent us both failed compressors, the drive and drive gear, shear coupling,  the FT-1 â€œsnotâ€ valve and the pressure relief tee setup.  We built one compressor out of the two failed units.  The 4 stripped studs were replaced with new studs and installed with Loctite.  The compressor was test run and produced 925 psi.  The pressure relief valve tee setup was tested â€“ it relieved normally -  rebuilt with a new piston, new seals in the one way checkvalves and the pressure set to 50 atm. (The pressure relief valve had a Teflon seal which was in very poor condition.) The snot valve was tested, flushed and retested.  The compressor, gaskets and drive unit were secured to one another in the proper alignment for the reinstall.

 

The air compressor was returned to the customer and it was reinstalled without attaching the steel air line. Everything was normal for about 1.5 hours of ground runs. 

 

A flight was completed with the steel coiled air line still not attached.  The flight was normal.

 

The steel line was reattached and 90 minutes of ground run time.  He noticed that pressure was not building as it should and opened the cowling  to find one of the 4 hold-down nuts backing off. He also reported that the other 3 nuts were not tight.  The owner drilled and safety wired the nuts.

 

(Note:  There is a CRITICAL clearance that is set between the bottom of the Stage I piston and the top of the Stage II cylinder.  Over-tightening these nuts will cause the top of the piston to hit the top of the Stage II cylinder.  Too much clearance and it bottoms out on the other end.)

 

We received the compressor and installed new studs and steel locknuts with Loctite.  The compressor has been returned but not run, yet.

 

Here is what we know:

1.       The FT-1 Snot valve is was flushed and functioning properly.

2.       The pressure relief valve tee and checkvalves were all tested and the system functioned normally on a bench test, with the pressure relief valve popping off at 750 psi. 

3.       A new steel line was provided to the customer, but I do not know if this was installed.

4.       On the 4th installation of the compressor, we returned the compressor, shear coupling, drive pad and gear tie-wrapped as a unit for correct clocking.  We received photo verification that the compressor drive was installed correctly.

5.       The compressor operated normally on the last run until the steel line was attached to it.  Then, 1 nut backed off and the other 3 were reported loose.  Hence, we replaced the hex nuts/lockwashers with steel locknuts in case the lockwashers had failed and that was the only problem on the last run.

6.       The force to shear the compressor studs is in excess of 22,000 lbs.  

7.       The shear coupling appears to be a factory unit.  A new one was sent to the customer, but returned back to me.

8.       The oil return holes in the accessory case are large and not plugged.

 

In the 20+ years that we have been overhauling air compressors, we have never encountered this problem.  Please use this problem as your own theoretical and reasoning challenge to put forth real possibilities â€“grasping at unicorns, rainbows or butterflies not allowed.  :  )

 

Jill

M-14P, Inc.

 

 

 

   	  Quote: 	
		  



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[b]

keithmckinley

Joined: 11 Aug 2008
Posts: 434

Posted: Tue Oct 15, 2013 6:36 pm Post subject: Re: Air Compressor (?) Issue

If this plane came from the east coast I know it well. I flew A LOT with the owner who had before the ins company sold it and don't ever remember hearing about a compressor issue. ever. I would guess there are some big time metallurgy issues after watching it burn.

Vic

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

Posted: Tue Oct 15, 2013 7:51 pm Post subject: Re: Air Compressor (?) Issue

Hello Jill,

I wonder why the shear pins did not snap before the studs let go - unless you did not really check this ? I suspect an insufficient oil supply to the compressor and  seized pistons. After the pins snapped the whole shear coupling may have seized again and consequently leading to breaking the studs. Did you look inside the compressor cylinders to check them for seizure ? With poor oil supply to the compressor drive I can imagine a snapped shear coupling will seize again in little time causing more damage. Please keep us posted with your findings.



   Cheers

    Vic

jan.mevis(at)informavia.b
Guest

Posted: Tue Oct 15, 2013 10:42 pm Post subject: Air Compressor (?) Issue

Probably a stupid remark, but are you sure that the shear coupling was OK?

I've seen shear couplings that were repaired with STEEL from nails.



Jan



From:  "jill(at)m-14p.com" <jill(at)m-14p.com>

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

Date:  Tuesday 15 October 2013 23:09

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

Subject:  Air Compressor (?) Issue



Group,

 

We have met up with a head scratcher.  I am throwing it out to the group to

chew on:

 

The Yak 52 owner purchased his aircraft on an insurance sale.  The aircraft

had been totaled because of an engine fire.  Attempts to talk to the

original owners and learn more about the aircraft¹s history have been

unsuccessful.  Originally, we were contacted because the air system was not

building pressure.  A photo sent by the owner, elicited a remark by me that

there seemed to be a lot of oil in the banjo/outlet valve fitting.  The

compressor itself was very dirty.

The owner cleaned the outlet valve with no appreciable change in output.

He then bought a  "NOS" comp from a private party, installed it and it

failed in 2.5 hours.  This compressor had actually been overhauled by us in

2006.  The nuts stripped off of the 4 studs on the bottom end of the

compressor (green case), allowing the top end off the compressor to hammer

up and down.  Oil was all over the back end of the engine.

 

The customer then sent his original compressor for overhaul and run on our

test bench.  He installed this overhauled compressor and it failed after 40

minutes in flight. This time the 4 studs sheared off of the bottom end of

the compressor.  

 

He sent us both failed compressors, the drive and drive gear, shear

coupling,  the FT-1 ³snot² valve and the pressure relief tee setup.  We

built one compressor out of the two failed units.  The 4 stripped studs were

replaced with new studs and installed with Loctite.  The compressor was test

run and produced 925 psi.  The pressure relief valve tee setup was tested 

it relieved normally -  rebuilt with a new piston, new seals in the one way

checkvalves and the pressure set to 50 atm. (The pressure relief valve had a

Teflon seal which was in very poor condition.) The snot valve was tested,

flushed and retested.  The compressor, gaskets and drive unit were secured

to one another in the proper alignment for the reinstall.

 

The air compressor was returned to the customer and it was reinstalled

without attaching the steel air line. Everything was normal for about 1.5

hours of ground runs.

 

A flight was completed with the steel coiled air line still not attached.

The flight was normal.

 

The steel line was reattached and 90 minutes of ground run time.  He noticed

that pressure was not building as it should and opened the cowling  to find

one of the 4 hold-down nuts backing off. He also reported that the other 3

nuts were not tight.  The owner drilled and safety wired the nuts.

 

(Note:  There is a CRITICAL clearance that is set between the bottom of the

Stage I piston and the top of the Stage II cylinder.  Over-tightening these

nuts will cause the top of the piston to hit the top of the Stage II

cylinder.  Too much clearance and it bottoms out on the other end.)

 

We received the compressor and installed new studs and steel locknuts with

Loctite.  The compressor has been returned but not run, yet.

 

Here is what we know:

1.       The FT-1 Snot valve is was flushed and functioning properly.



2.       The pressure relief valve tee and checkvalves were all tested and

the system functioned normally on a bench test, with the pressure relief

valve popping off at 750 psi.



3.       A new steel line was provided to the customer, but I do not know if

this was installed.



4.       On the 4th installation of the compressor, we returned the

compressor, shear coupling, drive pad and gear tie-wrapped as a unit for

correct clocking.  We received photo verification that the compressor drive

was installed correctly.



5.       The compressor operated normally on the last run until the steel

line was attached to it.  Then, 1 nut backed off and the other 3 were

reported loose.  Hence, we replaced the hex nuts/lockwashers with steel

locknuts in case the lockwashers had failed and that was the only problem on

the last run.



6.       The force to shear the compressor studs is in excess of 22,000 lbs

Vic

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

Posted: Wed Oct 16, 2013 3:38 am Post subject: Re: Air Compressor (?) Issue

........shear pins made from nails should be acceptable, more so than made from high tensile steel. They should go before more serious damage is done to the compressor.



  Vic

jan.mevis(at)informavia.b
Guest

Posted: Wed Oct 16, 2013 4:24 am Post subject: Air Compressor (?) Issue

As you say, they should, but I'd never install them Š



Jan



On 16/10/13 13:38, "Vic" <vicmolnar(at)aol.com> wrote:



 	  Quote: 	
		  



........shear pins made from nails should be acceptable, more so than

made from high tensile steel. They should go before more serious damage

is done to the compressor.



  Vic





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=410685#410685

dsavarese0812(at)bellsout
Guest

Posted: Wed Oct 16, 2013 4:35 am Post subject: Air Compressor (?) Issue

Is it possible when the "Cross" installed on the firewall, which you tested at the shop, it was disassembled and the check valve coming from the snot bottle to the cross was reversed?  ie: with the arrow pointing back toward the snot bottle line?  This would cause a huge amount of back pressure and no pop off of the pressure relief valve.

Dennis





        From: Jill Gernetzke <jill(at)m-14p.com>

 To: yak-list(at)matronics.com 

 Sent: Tuesday, October 15, 2013 4:09 PM

 Subject: Air Compressor (?) Issue

  

 

Group,

  

We have met up with a head scratcher.  I am throwing it out to the group to chew on:

  

The Yak 52 owner purchased his aircraft on an insurance sale.  The aircraft had been totaled because of an engine fire.  Attempts to talk to the original owners and learn more about the aircraftâ€™s history have been unsuccessful.  Originally, we were contacted because the air system was not building pressure.  A photo sent by the owner, elicited a remark by me that there seemed to be a lot of oil in the banjo/outlet valve fitting.  The compressor itself was very dirty.

The owner cleaned the outlet valve with no appreciable change in  output.

He then bought a  "NOS" comp from a private party, installed it and it failed in 2.5 hours.  This compressor had actually been overhauled by us in 2006.  The nuts stripped off of the 4 studs on the bottom end of the compressor (green case), allowing the top end off the compressor to hammer up and down.  Oil was all over the back end of the engine.

  

The customer then sent his original compressor for overhaul and run on our test bench.  He installed this overhauled compressor and it failed after 40 minutes in flight. This time the 4 studs sheared off of the bottom end of the compressor.  

  

He sent us both failed compressors, the drive and drive gear, shear coupling,  the FT-1 â€œsnotâ€ valve and the  pressure relief tee setup.  We built one compressor out of the two failed units.  The 4 stripped studs were replaced with new studs and installed with Loctite.  The compressor was test run and produced 925 psi.  The pressure relief valve tee setup was tested â€“ it relieved normally -  rebuilt with a new piston, new seals in the one way checkvalves and the pressure set to 50 atm. (The pressure relief valve had a Teflon seal which was in very poor condition.) The snot valve was tested, flushed and retested.  The compressor, gaskets and drive unit were secured to one another in the proper alignment for the reinstall.

  

The air compressor was returned to the customer and it was reinstalled without attaching the steel air line. Everything was normal for about 1.5 hours of ground runs. 

   

A flight was completed with the steel coiled air line still not attached.  The flight was normal.

  

The steel line was reattached and 90 minutes of ground run time.  He noticed that pressure was not building as it should and opened the cowling  to find one of the 4 hold-down nuts backing off. He also reported that the other 3 nuts were not tight.  The owner drilled and safety wired the nuts.

  

(Note:  There is a CRITICAL clearance that is set between the bottom of the Stage I piston and the top of the Stage II cylinder.  Over-tightening these nuts will cause the top of the piston to hit the top of the Stage II cylinder.  Too much clearance and it bottoms out on the other end.)

  

We received the compressor and installed new studs and steel locknuts with Loctite.  The compressor has been returned but not run, yet.

  

Here is what we know:

1.       The FT-1 Snot valve is was flushed and functioning properly.

2.       The pressure relief valve tee and checkvalves were all tested and the system functioned normally on a bench test, with the pressure relief valve popping off at 750 psi. 

3.       A new steel line was provided to the customer, but I do not know if this was installed.

4.       On the 4th installation of the compressor, we returned the compressor, shear coupling, drive pad and gear tie-wrapped as a unit for correct clocking.  We received photo verification that the compressor drive was installed correctly.

5.       The compressor operated normally on the last run until the steel line was attached to it.  Then, 1 nut backed off and the other 3 were  reported loose.  Hence, we replaced the hex nuts/lockwashers with steel locknuts in case the lockwashers had failed and that was the only problem on the last run.

6.       The force to shear the compressor studs is in excess of 22,000 lbs.  

7.       The shear coupling appears to be a factory unit.  A new one was sent to the customer, but returned back to me.

8.       The oil return holes in the accessory case are large and not  plugged.

  

In the 20+ years that we have been overhauling air compressors, we have never encountered this problem.  Please use this problem as your own theoretical and reasoning challenge to put forth real possibilities â€“grasping at unicorns, rainbows or butterflies not allowed.  :  )

  

Jill

M-14P, Inc.

  

  

  



    	  Quote: 	
		  http://www.matronics.com/Navigator?Yak-Listhttp://=======================


	






 

 

  

 [quote][b]

jill(at)m-14p.com
Guest

Posted: Wed Oct 16, 2013 5:31 am Post subject: Air Compressor (?) Issue

Group,

 

Replies to issues brought up in your posts:

 

<![if !supportLists]>1.       <![endif]> None of the pistons were seized.  In fact, they were all oily.

<![if !supportLists]>2.       <![endif]>The original steel line, as reported by the owner, was free of restrictions.   I sent him a new one because he said the outlet valve/banjo departed the aircraft on the first failure. (That is another head scratcher.)  I don’t know if the new line is installed or not.

<![if !supportLists]>3.       <![endif]> Again, we tested the snot valve and the pressure relief valve tee was sent back to him as a unit – ready to bolt back on the aircraft.

<![if !supportLists]>4.       <![endif]>I sent the customer a new shear coupling and it was returned to me.  The old coupling looked like a factory unit, but as we know, there was a batch of Yaks that went out the door with shear pins that were too hard.  Years ago, we had a metallurgist analyze the hardness of the rivets for the “before driven” value and we have machined our own rivets for the shear couplings.  We know our rivets are the correct hardness…..anything else you are putting in from ACE hardware, etc. is a game of roulette unless you have the hardness value before and after driving the rivets.  We will repin your shear coupling, we do not sell the pins.

 

 

Never thought that MMO might be the solution and magic elixir!  ;  )

 

Jill

  [quote][b]

mark.bitterlich(at)navy.m
Guest

Posted: Wed Oct 16, 2013 8:18 am Post subject: Air Compressor (?) Issue

Jill, some suggestions if I may. 



Step number one: 



Have the owner disconnect the steel air line that goes from the compressor to the snot valve (at the compressor side).  Loan him an adapter fitting so that he can go from that line to an AN fitting.  



Then with a regulated air supply (from a bottle), have him apply air to the airplane (through the steel line).  I.E. The air bottle will now act as the source of air, as the compressor normally would.  Check to see that the aircraft bottles pressurize normally.  Increase pressure to 735 PSI and insure the pop-off valve functions normally.  



Close off the air bottle but do not release pressure.  



Now open the snot valve and insure air is released AND THERE IS NO FLUID IN IT WHAT-SO-EVER!  If OIL comes out, we really want to know that! 



This test takes all conjecture and guess work out of the: "Is something wrong with the airplane?" question, and this test can still be done now.   I suspect it will check good, but you never know... in any case, if there is anything wrong, or leaks, or whatever, this test will find it.  I have done it myself.  



Moving on, the short version of your story is that he lost the ability to pressurize his tanks, changed the compressor and things got worse from there.  



I have to tell you that I find it hard to imagine that air pressure could cause the kind of damage to the compressor studs and nuts that you have described.  If a compressor is working against head pressure (AIR), it usually just eventually stops making more pressure and does not beat itself to death and blow the head off.  Anyway, not one this small with this low of a volume.  Of course I could be wrong.... but......moving on....... 



That said, if the first test above does not find anything wrong... And I repeat ONLY if the above test was done and again I repeat... checked good, then my focus would go back to the compressor and drive assembly itself.  



My suspicion at this point would be that there is some kind of internal crack in the drive assembly (or something else internal) that is allowing oil into the compression path.  If you get a FLUID into a compressor like this, well... FLUIDS (like oil) do not compress like air does, and you get the exact duplicate of a hydraulic lock in our M-14 engines.  A situation I am sure you are an expert at.  A fluid in ANY kind of compressor, whether it be an air compressor or an engine cylinder and piston is disastrous and SOMETHING HAS TO GIVE.  Something mechanical.   In this case, I believe that is what is blowing your compressor right off the top of the drive assembly.  You would have to tell me if the same drive assembly was used both times.  However, this would also explain the amount of oil he is seeing in the outlet.  



All guesswork, but logical anyway. 



Mark Bitterlich



--

cjpilot710(at)aol.com
Guest

Posted: Tue Oct 29, 2013 12:02 pm Post subject: Air Compressor (?) Issue

Doc, 

I'm here at KMGM until 1630 (I've got be copilot on the 17 this evening).  We'll be leaving tomorrow about noon.

Pappy. 



Sent from my iPad from some where on The 3rd rock from the Sun.



On Oct 15, 2013, at 20:46, "Roger Kemp M.D." <viperdoc(at)mindspring.com (viperdoc(at)mindspring.com)> wrote:

[quote]One thought, since there was a fire that involved the firewall were the check valves at the pop off valve rebuilt or replaced. Is it possible that the lower check valve between the snot bottle and the pop off valve and the filter are reversed. Instead of the one way valve arrow on the check valve pointing to the filter and theophylline off valve could it be pointing at the snot bottle. Did y'all re-assemble the H or was it done in the field? Is the filter patent or is it clogged up from carbon deposited? 

I saw your #2 in the summary list that referred to testing the H setup. Was it disassemble after ya'll shipped it. As you know the check valve direction will have a big impact on air flow. 

Just a though.

Doc



Sent from my iPad



On Oct 15, 2013, at 4:09 PM, "Jill Gernetzke" <jill(at)m-14p.com (jill(at)m-14p.com)> wrote:

 	  Quote: 	
		    <![endif]-->   <![endif]-->

Group,

 

We have met up with a head scratcher.  I am throwing it out to the group to chew on:

 

The Yak 52 owner purchased his aircraft on an insurance sale.  The aircraft had been totaled because of an engine fire.  Attempts to talk to the original owners and learn more about the aircraftâ€™s history have been unsuccessful.  Originally, we were contacted because the air system was not building pressure.  A photo sent by the owner, elicited a remark by me that there seemed to be a lot of oil in the banjo/outlet valve fitting.  The compressor itself was very dirty.

The owner cleaned the outlet valve with no appreciable change in output.

He then bought a  "NOS" comp from a private party, installed it and it failed in 2.5 hours.  This compressor had actually been overhauled by us in 2006.  The nuts stripped off of the 4 studs on the bottom end of the compressor (green case), allowing the top end off the compressor to hammer up and down.  Oil was all over the back end of the engine.

 

The customer then sent his original compressor for overhaul and run on our test bench.  He installed this overhauled compressor and it failed after 40 minutes in flight. This time the 4 studs sheared off of the bottom end of the compressor.  

 

He sent us both failed compressors, the drive and drive gear, shear coupling,  the FT-1 â€œsnotâ€ valve and the pressure relief tee setup.  We built one compressor out of the two failed units.  The 4 stripped studs were replaced with new studs and installed with Loctite.  The compressor was test run and produced 925 psi.  The pressure relief valve tee setup was tested â€“ it relieved normally -  rebuilt with a new piston, new seals in the one way checkvalves and the pressure set to 50 atm. (The pressure relief valve had a Teflon seal which was in very poor condition.) The snot valve was tested, flushed and retested.  The compressor, gaskets and drive unit were secured to one another in the proper alignment for the reinstall.

 

The air compressor was returned to the customer and it was reinstalled without attaching the steel air line. Everything was normal for about 1.5 hours of ground runs. 

 

A flight was completed with the steel coiled air line still not attached.  The flight was normal.

 

The steel line was reattached and 90 minutes of ground run time.  He noticed that pressure was not building as it should and opened the cowling  to find one of the 4 hold-down nuts backing off. He also reported that the other 3 nuts were not tight.  The owner drilled and safety wired the nuts.

 

(Note:  There is a CRITICAL clearance that is set between the bottom of the Stage I piston and the top of the Stage II cylinder.  Over-tightening these nuts will cause the top of the piston to hit the top of the Stage II cylinder.  Too much clearance and it bottoms out on the other end.)

 

We received the compressor and installed new studs and steel locknuts with Loctite.  The compressor has been returned but not run, yet.

 

Here is what we know:

1.       The FT-1 Snot valve is was flushed and functioning properly.

2.       The pressure relief valve tee and checkvalves were all tested and the system functioned normally on a bench test, with the pressure relief valve popping off at 750 psi. 

3.       A new steel line was provided to the customer, but I do not know if this was installed.

4.       On the 4th installation of the compressor, we returned the compressor, shear coupling, drive pad and gear tie-wrapped as a unit for correct clocking.  We received photo verification that the compressor drive was installed correctly.

5.       The compressor operated normally on the last run until the steel line was attached to it.  Then, 1 nut backed off and the other 3 were reported loose.  Hence, we replaced the hex nuts/lockwashers with steel locknuts in case the lockwashers had failed and that was the only problem on the last run.

6.       The force to shear the compressor studs is in excess of 22,000 lbs.  

7.       The shear coupling appears to be a factory unit.  A new one was sent to the customer, but returned back to me.

8.       The oil return holes in the accessory case are large and not plugged.

 

In the 20+ years that we have been overhauling air compressors, we have never encountered this problem.  Please use this problem as your own theoretical and reasoning challenge to put forth real possibilities â€“grasping at unicorns, rainbows or butterflies not allowed.  :  )

 

Jill

M-14P, Inc.

 

 

 

   	  Quote: 	
		  



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[b]

viperdoc(at)mindspring.co
Guest

Posted: Tue Oct 29, 2013 12:25 pm Post subject: Air Compressor (?) Issue

Pappy, how long are you flying the 17 this evening? I need to run up to 08a after I finish office procedures around 1530. 08a is 20 min N then MGM is 40 min S from 08A down I 65. 

Doc



Sent from my iPad



On Oct 29, 2013, at 3:00 PM, James Goolsby <cjpilot710(at)aol.com (cjpilot710(at)aol.com)> wrote:

[quote]Doc, 

I'm here at KMGM until 1630 (I've got be copilot on the 17 this evening).  We'll be leaving tomorrow about noon.

Pappy. 



Sent from my iPad from some where on The 3rd rock from the Sun.



On Oct 15, 2013, at 20:46, "Roger Kemp M.D." <viperdoc(at)mindspring.com (viperdoc(at)mindspring.com)> wrote:

 	  Quote: 	
		  One thought, since there was a fire that involved the firewall were the check valves at the pop off valve rebuilt or replaced. Is it possible that the lower check valve between the snot bottle and the pop off valve and the filter are reversed. Instead of the one way valve arrow on the check valve pointing to the filter and theophylline off valve could it be pointing at the snot bottle. Did y'all re-assemble the H or was it done in the field? Is the filter patent or is it clogged up from carbon deposited? 

I saw your #2 in the summary list that referred to testing the H setup. Was it disassemble after ya'll shipped it. As you know the check valve direction will have a big impact on air flow. 

Just a though.

Doc



Sent from my iPad



On Oct 15, 2013, at 4:09 PM, "Jill Gernetzke" <jill(at)m-14p.com (jill(at)m-14p.com)> wrote:

 	  Quote: 	
		    <![endif]-->   <![endif]-->

Group,

 

We have met up with a head scratcher.  I am throwing it out to the group to chew on:

 

The Yak 52 owner purchased his aircraft on an insurance sale.  The aircraft had been totaled because of an engine fire.  Attempts to talk to the original owners and learn more about the aircraftâ€™s history have been unsuccessful.  Originally, we were contacted because the air system was not building pressure.  A photo sent by the owner, elicited a remark by me that there seemed to be a lot of oil in the banjo/outlet valve fitting.  The compressor itself was very dirty.

The owner cleaned the outlet valve with no appreciable change in output.

He then bought a  "NOS" comp from a private party, installed it and it failed in 2.5 hours.  This compressor had actually been overhauled by us in 2006.  The nuts stripped off of the 4 studs on the bottom end of the compressor (green case), allowing the top end off the compressor to hammer up and down.  Oil was all over the back end of the engine.

 

The customer then sent his original compressor for overhaul and run on our test bench.  He installed this overhauled compressor and it failed after 40 minutes in flight. This time the 4 studs sheared off of the bottom end of the compressor.  

 

He sent us both failed compressors, the drive and drive gear, shear coupling,  the FT-1 â€œsnotâ€ valve and the pressure relief tee setup.  We built one compressor out of the two failed units.  The 4 stripped studs were replaced with new studs and installed with Loctite.  The compressor was test run and produced 925 psi.  The pressure relief valve tee setup was tested â€“ it relieved normally -  rebuilt with a new piston, new seals in the one way checkvalves and the pressure set to 50 atm. (The pressure relief valve had a Teflon seal which was in very poor condition.) The snot valve was tested, flushed and retested.  The compressor, gaskets and drive unit were secured to one another in the proper alignment for the reinstall.

 

The air compressor was returned to the customer and it was reinstalled without attaching the steel air line. Everything was normal for about 1.5 hours of ground runs. 

 

A flight was completed with the steel coiled air line still not attached.  The flight was normal.

 

The steel line was reattached and 90 minutes of ground run time.  He noticed that pressure was not building as it should and opened the cowling  to find one of the 4 hold-down nuts backing off. He also reported that the other 3 nuts were not tight.  The owner drilled and safety wired the nuts.

 

(Note:  There is a CRITICAL clearance that is set between the bottom of the Stage I piston and the top of the Stage II cylinder.  Over-tightening these nuts will cause the top of the piston to hit the top of the Stage II cylinder.  Too much clearance and it bottoms out on the other end.)

 

We received the compressor and installed new studs and steel locknuts with Loctite.  The compressor has been returned but not run, yet.

 

Here is what we know:

1.       The FT-1 Snot valve is was flushed and functioning properly.

2.       The pressure relief valve tee and checkvalves were all tested and the system functioned normally on a bench test, with the pressure relief valve popping off at 750 psi. 

3.       A new steel line was provided to the customer, but I do not know if this was installed.

4.       On the 4th installation of the compressor, we returned the compressor, shear coupling, drive pad and gear tie-wrapped as a unit for correct clocking.  We received photo verification that the compressor drive was installed correctly.

5.       The compressor operated normally on the last run until the steel line was attached to it.  Then, 1 nut backed off and the other 3 were reported loose.  Hence, we replaced the hex nuts/lockwashers with steel locknuts in case the lockwashers had failed and that was the only problem on the last run.

6.       The force to shear the compressor studs is in excess of 22,000 lbs.  

7.       The shear coupling appears to be a factory unit.  A new one was sent to the customer, but returned back to me.

8.       The oil return holes in the accessory case are large and not plugged.

 

In the 20+ years that we have been overhauling air compressors, we have never encountered this problem.  Please use this problem as your own theoretical and reasoning challenge to put forth real possibilities â€“grasping at unicorns, rainbows or butterflies not allowed.  :  )

 

Jill

M-14P, Inc.

 

 

 

   	  Quote: 	
		  



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