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YAK Pneumatic Lubricant (long post)

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Rob Rowe

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

Posted: Wed Sep 02, 2015 7:26 am Post subject: YAK Pneumatic Lubricant (long post)

I've been researching YAK pneumatic lubricants over some years and with recent posts on this topic (and some recent progress) I thought I'd share my thoughts for your consideration.



1 - Nowhere in the YAK (-52) maintenance manual does it refer to using alcohol/glycerine to lubricate the pneumatic system. The only reference you'll find for this concoction is for drying spark plugs after they've been cleaned. Glycerine is a viscous humectant (a substance that retains moisture) that is only soluble in alcohol or water, hence to get it into the system alcohol has to be added to thin it out. Once introduced at best it will absorb some moisture, but then all of this mix needs to be blown out as soon as possible. Otherwise the alcohol quickly evaporates leaving the viscous Glycerine residue and moisture in the horizontal pipe runs (typically). This then tends to trap more moisture in these runs causing the most common long term failure mode of internal pin hole corrosion. 



2 – So what is the correct lubricant then? The maintenance manual states Fluid 132-25 should be used to lubricate the pneumatic system. But from what I can ascertain Fluid 132-25 went out of production sometime in the 1980’s. Given the small quantities needed you could lubricate pretty well every -52 built with a single 200 litre (45 US gallon) drum per annum … so commercially unviable would be my guess as to its demise. Therefore alcohol / glycerine were probably used as a substitute as it was readily to hand for plug maintenance.  I’d also speculate that with DOSAAF utilisation aircraft would be completely stripped down every 5 years, so any problem with pipe corrosion probably wouldn’t have time to manifest.



3 – To compound this issue the build-up of glycerine over time in the pipe runs (which seems to harden - reaction with compressor acidic oil / carbon?) also reduces the air flow and slows the gear operational times. This has led to a number of aircraft having their air flow restrictors removed from the (rear) gear selector connections to help bring extension/retraction times back within specification. While this works it may lead to a more insidious problem of higher engagement speeds with the gear up-locks at the end of the actuator’s travel. This energy then gets absorbed by mounting plates inside the wing that may create cracks in them (the subject of a YDB document in 2009 requiring borescope inspection). At first this was thought to be just related to shock loads from gear-up incident aircraft, but has been found to be more widespread across the fleet here in the UK. Giving more credibility to it being a consequence of gear engagement speed.



4 – Addressing this issue in 2010 I tried to source Fluid 132-25, but while a few East European companies claim they can produce it they never seem to have any stock or require vast minimum order quantities to be made. Finally through the personal contacts of a UK based Russian engineer a chemical company in the Ukraine agreed to make a few litres in their labs, which has been used on some YAKs here in the UK (including mine) for the last few years. With the current ‘difficulties’ in the Ukraine it’s unlikely to be repeatable source. The results on my -52 have been positive, the gear cycle times noticeably decreased through improved lubrication to the extent that the air flow restrictors could be re-installed. Annual monitoring of the up-lock related internal cracks have shown no further increase. Better still the UK CAA allows its use, as an originally specified lubricant, without further approval.



5 – So what is Fluid 132-25? The Russian GOST 10957-74 specification describes it as an organo-silicon, and on closer examination it’s a Polyethylsiloxane (PES), the ‘ethyl’ bit gives good low temperature viscosity pour characteristics (-70°C). Essentially a silicone fluid that‘s a moisture displacement agent and lubricant. But PES products are niche and difficult to source, not too surprisingly given the above history. However having done some further research into this there is a Dow Corning product that might be a suitable alternative. While it’s a Polydimethylsiloxane (PDMS) the low temperature pour characteristics (-65°C) are very nearly as good and it’s also available within the lower viscosity range of the Fluid 132-25 spec (190-290cSt). Having readily sourced some commercially in the UK in a 1 litre quantity I’ve saturated some old pneumatic seals in this PDMS silicone fluid for some 6 months now with no adverse effects on the seal’s apparent integrity. There has been a seal mass reduction during this time of 3-4%, although this may be due to contaminant leaching from the old seals. I’m now at the stage of approaching the UK CAA for a minor modification approval for use on UK registered YAKs.



AS SUCH I HAVE TO RAISE A WARNING THAT I TAKE NO RESPONSIBILTY WHATSOEVER FOR ANY ADVERSE EFFECTS ON YOUR AIRCRAFT AND IF YOU CHOOSE TO USE IT THEN IT’S COMPLETELY AT YOUR OWN VOLITION AND RISK.



The product is Dow Corning Xiameter PMX-200 Silicone Fluid (200cSt) and is available in a variety of viscosities. The 200cSt viscosity is the only one closely meeting the Fluid 132-25 specification.



Note - ‘PMX-200’ is a brand name not a viscosity rating; hence PMX-200 (200cSt) is the specific viscosity required of this product.



I’ve posted PDF’s of the Russian GOST 10957-74 (Cyrillic) and Dow Corning PMX-200 specifications for reference.



Hope this is of some use to the YAK community.



Brgds, Rob R.

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mark.bitterlich(at)navy.m
Guest

Posted: Wed Sep 02, 2015 7:45 am Post subject: YAK Pneumatic Lubricant (long post)

I'd say that about sums it up.  My take away from this excellent write-up is that a lot of people have probably been putting the wrong fluid into their systems.



Mark

--

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jan.mevis(at)informavia.b
Guest

Posted: Wed Sep 02, 2015 11:10 am Post subject: YAK Pneumatic Lubricant (long post)

Thanks a lot Rob! This is impressive! I'll read these documents carefully.



I was told years ago that the Soviets stopped making this fluid in the

eighties. 

The glycerine/ethanol is an "ersatz" but I doubt it that the Soviet

mechanics would have used it without any instructions from above.



Anyway, as you state it very clearly, it's every Yak drivers personal

responsibility, and I absolutely concur.

So I stick with what the Lithuanians and the Russians do, in the past and

today. Until I'm convinced that the PMX-200 is a better product.



And also I have the gear thoroughly checked each year.



BR,



Jan



On 02/09/15 17:26, "Rob Rowe" <owner-yak-list-server(at)matronics.com on

behalf of yak-list(at)robrowe.plus.com> wrote:



 	  Quote: 	
		  



I've been researching YAK pneumatic lubricants over some years and with

recent posts on this topic (and some recent progress) I thought I'd share

my thoughts for your consideration.



1 - Nowhere in the YAK (-52) maintenance manual does it refer to using

alcohol/glycerine to lubricate the pneumatic system. The only reference

you'll find for this concoction is for drying spark plugs after they've

been cleaned. Glycerine is a viscous humectant (a substance that retains

moisture) that is only soluble in alcohol or water, hence to get it into

the system alcohol has to be added to thin it out. Once introduced at

best it will absorb some moisture, but then all of this mix needs to be

blown out as soon as possible. Otherwise the alcohol quickly evaporates

leaving the viscous Glycerine residue and moisture in the horizontal pipe

runs (typically). This then tends to trap more moisture in these runs

causing the most common long term failure mode of internal pin hole

corrosion. 



2 â So what is the correct lubricant then? The maintenance manual

states Fluid 132-25 should be used to lubricate the pneumatic system. But

from what I can ascertain Fluid 132-25 went out of production sometime in

the 1980âs. Given the small quantities needed you could lubricate

pretty well every -52 built with a single 200 litre (45 US gallon) drum

per annum â¦ so commercially unviable would be my guess as to its

demise. Therefore alcohol / glycerine were probably used as a substitute

as it was readily to hand for plug maintenance.  Iâd also speculate

that with DOSAAF utilisation aircraft would be completely stripped down

every 5 years, so any problem with pipe corrosion probably wouldnât

have time to manifest.



3 â To compound this issue the build-up of glycerine over time in the

pipe runs (which seems to harden - reaction with compressor acidic oil /

carbon?) also reduces the air flow and slows the gear operational times.

This has led to a number of aircraft having their air flow restrictors

removed from the (rear) gear selector connections to help bring

extension/retraction times back within specification. While this works it

may lead to a more insidious problem of higher engagement speeds with the

gear up-locks at the end of the actuatorâs travel. This energy then

gets absorbed by mounting plates inside the wing that may create cracks

in them (the subject of a YDB document in 2009 requiring borescope

inspection). At first this was thought to be just related to shock loads

from gear-up incident aircraft, but has been found to be more widespread

across the fleet here in the UK. Giving more credibility to it being a

consequence of gear engagement speed.



4 â Addressing this issue in 2010 I tried to source Fluid 132-25, but

while a few East European companies claim they can produce it they never

seem to have any stock or require vast minimum order quantities to be

made. Finally through the personal contacts of a UK based Russian

engineer a chemical company in the Ukraine agreed to make a few litres in

their labs, which has been used on some YAKs here in the UK (including

mine) for the last few years. With the current âdifficultiesâ in the

Ukraine itâs unlikely to be repeatable source. The results on my -52

have been positive, the gear cycle times noticeably decreased through

improved lubrication to the extent that the air flow restrictors could be

re-installed. Annual monitoring of the up-lock related internal cracks

have shown no further increase. Better still the UK CAA allows its use,

as an originally specified lubricant, without further approval.



5 â So what is Fluid 132-25? The Russian GOST 10957-74 specification

describes it as an organo-silicon, and on closer examination itâs a

Polyethylsiloxane (PES), the âethylâ bit gives good low temperature

viscosity pour characteristics (-70Â°C). Essentially a silicone fluid

thatâs a moisture displacement agent and lubricant. But PES products

are niche and difficult to source, not too surprisingly given the above

history. However having done some further research into this there is a

Dow Corning product that might be a suitable alternative. While itâs a

Polydimethylsiloxane (PDMS) the low temperature pour characteristics

(-65Â°C) are very nearly as good and itâs also available within the

lower viscosity range of the Fluid 132-25 spec (190-290cSt). Having

readily sourced some commercially in the UK in a 1 litre quantity Iâve

saturated some old pneumatic seals in this PDMS silicone fluid for some 6

months now with no adverse effects on the sealâs apparent inte!

 grity. There has been a seal mass reduction during this time of 3-4%,

although this may be due to contaminant leaching from the old seals.

Iâm now at the stage of approaching the UK CAA for a minor modification

approval for use on UK registered YAKs.



AS SUCH I HAVE TO RAISE A WARNING THAT I TAKE NO RESPONSIBILTY WHATSOEVER

FOR ANY ADVERSE EFFECTS ON YOUR AIRCRAFT AND IF YOU CHOOSE TO USE IT THEN

ITâS COMPLETELY AT YOUR OWN VOLITION AND RISK.



The product is Dow Corning Xiameter PMX-200 Silicone Fluid (200cSt) and

is available in a variety of viscosities. The 200cSt viscosity is the

only one closely meeting the Fluid 132-25 specification.



Note - âPMX-200â is a brand name not a viscosity rating; hence

PMX-200 (200cSt) is the specific viscosity required of this product.



Iâve posted PDFâs of the Russian GOST 10957-74 (Cyrillic) and Dow

Corning PMX-200 specifications for reference.



Hope this is of some use to the YAK community.



Brgds, Rob R.





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=446686#446686





Attachments: 



http://forums.matronics.com//files/tds_pmx200_1000cs_602.pdf

http://forums.matronics.com//files/gost_10957_74_645.pdf

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Cliff.Coy

Joined: 03 Mar 2007
Posts: 46

Posted: Thu Sep 10, 2015 7:45 am Post subject: YAK Pneumatic Lubricant (long post)

Don't know how or why I received this email thread but...



We've been lubricating actuators, uplocks, and valves for something

like....20 years with Royco 43 Pneumatic system grease with excellent

results.



Royco only sells No.43 in 6.5# cans but commercially available greases

meeting the MIL-G-4343 Pneumatic System Grease specification are sold under

the names JetLube No.33 or Molycote 55M.



The glycerin/alcohol mixture was never meant as a lubricant--merely the

final drying step after the air/water separator and filter assemblies

before the pop-off valve.



As is evidenced by the oily mess seen at the exhaust ports of the pop-off

valve, the glycerin/alcohol step is a good idea!



FYI I've uploaded a lot of our collected information about Yak aircraft

(manuals,pictures,diagrams) here:



https://drive.google.com/open?id=0B_E0KXhypQtgejFDendsZmZZaEk



Feel free to peruse and if you have a good addition to make, please send it

on over.



Cheers,

Cliff





On Wed, Sep 2, 2015 at 3:07 PM, Jan Mevis <jan.mevis(at)informavia.be> wrote:



[quote] 



 Thanks a lot Rob! This is impressive! I'll read these documents carefully

- The Matronics Yak-List Email Forum -

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jan.mevis(at)informavia.b
Guest

Posted: Thu Sep 10, 2015 9:43 am Post subject: YAK Pneumatic Lubricant (long post)

Thanks Cliff! Awesome!



Jan



From:  <owner-yak-list-server(at)matronics.com> on behalf of Cliff Coy

<cliff.coy(at)gmail.com>

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

Date:  Thursday 10 September 2015 17:42

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

Subject:  Re: YAK Pneumatic Lubricant (long post)



Don't know how or why I received this email thread but...



We've been lubricating actuators, uplocks, and valves for something

like....20 years with Royco 43 Pneumatic system grease with excellent

results.



Royco only sells No.43 in 6.5# cans but commercially available greases

meeting the MIL-G-4343 Pneumatic System Grease specification are sold under

the names JetLube No.33 or Molycote 55M.



The glycerin/alcohol mixture was never meant as a lubricant--merely the

final drying step after the air/water separator and filter assemblies before

the pop-off valve.



As is evidenced by the oily mess seen at the exhaust ports of the pop-off

valve, the glycerin/alcohol step is a good idea!



FYI I've uploaded a lot of our collected information about Yak aircraft

(manuals,pictures,diagrams) here:



https://drive.google.com/open?id=0B_E0KXhypQtgejFDendsZmZZaEk

<https://drive.google.com/open?id=0B_E0KXhypQtgejFDendsZmZZaEk>



Feel free to peruse and if you have a good addition to make, please send it

on over.



Cheers,

Cliff





On Wed, Sep 2, 2015 at 3:07 PM, Jan Mevis <jan.mevis(at)informavia.be> wrote:

[quote] 

 

 Thanks a lot Rob! This is impressive! I'll read these documents carefully

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