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Super-cool oil temp
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apatton2

Joined: 17 Jan 2018
Posts: 32

Posted: Wed Jan 17, 2018 10:44 am Post subject: Super-cool oil temp

Hi All,

I recently acquired a Yak-50 from the UK (the former G-JYAK). I continue to work on getting it into tune (have replaced the carburetor and mags with overhauled units).



When warm it runs very smoothly and well, developing at least book power (>=8.85 potatoes MP on takeoff). Engine is the stock M14P... only mods are the auto ignition harness and an intake drain kit.



However, the oil temp takes a very long time to come up to 40degC on start. Overnight temps in my area (NorCal) get as cold as 5degC but are generally warmer. However, upon pulling the airplane out of the hangar and starting it, oil temp reads zero C, and will take 20min to get to 40 degC. In fact, after as much at 5min after engine start, the oil temp indicator still indicates 0degC.



This isn't great as I believe that the prolonged run at low power begins to foul plugs. When it's warmed up and motoring at 82% / 7 potatoes in high-power cruise, oil temp needle tends to "stand straight up" at 70-80deg C.



I'm wondering about 2 potential causes:

1. Is there a variable problem with the indicator? I.e. inaccurate at low power settings/low temps but fine at higher power settings.

2. Could there be some abnormal oil circulation, especially at low power settings, that is allowing cold oil to stagnate around the temp probe for awhile, even after startup.



Every other indication, as far as I can tell, is normal. CHT temps will come up to ~ 75-100degC while waiting for the oil temp to come up.



Any thoughts would be greatly appreciated.

Thanks!

Andrew

_________________
Andrew Patton
Yak-50
San Francisco, CA

bmsim

Joined: 02 Jun 2009
Posts: 32
Location: Alabama

Posted: Wed Jan 17, 2018 10:58 am Post subject: Re: Super-cool oil temp

I'm not an expert, but there's a lot of oil to bring up to temp from those low temps. I don't have to deal with temps quite that low, but I bought an oil heater and a small bathroom heater to help. I turn the heaters on the night before I plan to fly, and oil is much closer to temp when I get ready. I wired the oil heater to a switched female plug that accepts a computer power cord (stays with the Yak), so I just leave the Yak plugged in and switch the heater on and off at the plugin.



For the air heater, I found a small 250 watt heater at a department store (walmart) for $10. It is not much bigger than a brick and with slide in/out of the cowl without opening anything up. It is a bit underpowered, but does significantly raise the temp inside the cowl.



Not a direct answer to your post, but I just wanted to provide some thoughts on heating.

Ernie

Joined: 11 Jan 2006
Posts: 513

Posted: Wed Jan 17, 2018 11:04 am Post subject: Super-cool oil temp

Close the gills.



On Wed, Jan 17, 2018 at 8:47 PM apatton2 <apatton(at)alumni.princeton.edu (apatton(at)alumni.princeton.edu)> wrote:



 	  Quote: 	
		  --> Yak-List message posted by: "apatton2" <apatton(at)alumni.princeton.edu (apatton(at)alumni.princeton.edu)>

 

 Hi All,

 I recently acquired a Yak-50 from the UK (the former G-JYAK). I continue to work on getting it into tune (have replaced the carburetor and mags with overhauled units).

 

 When warm it runs very smoothly and well, developing at least book power (>=8.85 potatoes MP on takeoff). Engine is the stock M14P... only mods are the auto ignition harness and an intake drain kit.

 

 However, the oil temp takes a very long time to come up to 40degC on start. Overnight temps in my area (NorCal) get as cold as 5degC but are generally warmer. However, upon pulling the airplane out of the hangar and starting it, oil temp reads zero C, and will take 20min to get to 40 degC. In fact, after as much at 5min after engine start, the oil temp indicator still indicates 0degC.

 

 This isn't great as I believe that the prolonged run at low power begins to foul plugs. When it's warmed up and motoring at 82% / 7 potatoes in high-power cruise, oil temp needle tends to "stand straight up" at 70-80deg C.

 

 I'm wondering about 2 potential causes:

 1. Is there a variable problem with the indicator? I.e. inaccurate at low power settings/low temps but fine at higher power settings.

 2. Could there be some abnormal oil circulation, especially at low power settings, that is allowing cold oil to stagnate around the temp probe for awhile, even after startup.

 

 Every other indication, as far as I can tell, is normal. CHT temps will come up to ~ 75-100degC while waiting for the oil temp to come up.

 

 Any thoughts would be greatly appreciated.

 Thanks!

 Andrew

 

 --------

 Andrew Patton

 Yak-50

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=477374#477374

 

 

 

 

 

 

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richard.goode(at)russiana
Guest

Posted: Wed Jan 17, 2018 8:01 pm Post subject: Super-cool oil temp

Hello Andrew,



A number of the oil coolers have a thermostatic bypass, and I suspect yours

is remaining fully open so the entire oil system has to be warmed up before

you start getting an indication on the gauge, which will take far longer.



Richard



Rhodds Farm 

Lyonshall 

Hereford 

HR5 3LW 

United Kingdom 

 Tel: +94 (0) 81 241 5137 (Sri Lanka)

Tel:   +44 (0) 1544 340120 

Fax:  +44 (0) 1544 340129 

www.russianaeros.com

I’m currently in Sri Lanka but this Mail is working,and my local phone is

+94 779 132 160.

--

apatton2

Joined: 17 Jan 2018
Posts: 32

Posted: Wed Jan 17, 2018 8:37 pm Post subject: Re: Super-cool oil temp

Re: "close the gills" -  everything is closed (always is on warmup... I have several hundred hours in 50s and 52s).



Hi Richard - thanks for the note! My last -50 (a 1982 model with series 1 engine) came up to temp very rapidly and would seem to almost always stay cool.



I was wondering if there was any thermostatic regulation function in the oil system other than the manually actuated oil cooler door. Since I haven't seen anything that looked like a bypass valve for the oil cooler, I assumed that wasn't the case (I could be missing it, though). That said, I didn't think it would actually be built into the cooler itself!



I'll look again at some of the translated documents that I have to see if any light can be shed on this. But if that's the case and this valve is "stuck" open, then that would explain the observed phenomena.

Best,

Andrew

_________________
Andrew Patton
Yak-50
San Francisco, CA

cjpilot710(at)aol.com
Guest

Posted: Wed Jan 17, 2018 9:44 pm Post subject: Super-cool oil temp

You might also put a restrictor plate on the oil cooler intake.

Jim "Pappy" Goolsby

--

richard.goode(at)russiana
Guest

Posted: Wed Jan 17, 2018 10:19 pm Post subject: Super-cool oil temp

Hello Andrew,



I'm in Sri Lanka and therefore don't have access to all my technical papers

in the UK. But I am pretty sure that all or some of the oil coolers have a

thermostatic bypass valve, and until this opens, no oil goes through the oil

cooler. I suspect yours is sticking, and therefore the oil is continuing to

circulate through the oil cooler, and that is your problem.



I will investigate this more and that you know options, but I suspect we

could obtain a new valve.



Regards



Richard



Rhodds Farm 

Lyonshall 

Hereford 

HR5 3LW 

United Kingdom 

 Tel: +94 (0) 81 241 5137 (Sri Lanka)

Tel:   +44 (0) 1544 340120 

Fax:  +44 (0) 1544 340129 

www.russianaeros.com

I’m currently in Sri Lanka but this Mail is working,and my local phone is

+94 779 132 160.

--

apatton2

Joined: 17 Jan 2018
Posts: 32

Posted: Thu Jan 18, 2018 2:56 pm Post subject: Re: Super-cool oil temp

Doing some additional detective work... seems like replacing the "thermo-valve" was one of the very first service bulletins. But the details of this are lost to me (and don't affect my s/n).



Any chance the original SB exists somewhere (and might even be in English  )?

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_________________
Andrew Patton
Yak-50
San Francisco, CA

mark.bitterlich(at)navy.m
Guest

Posted: Fri Jan 19, 2018 10:08 am Post subject: Super-cool oil temp

Richard, I happen to have some knowledge on this topic.



Very early YAK-50's came with what guys in this country call a "Veritherm", but in truth is nothing but a thermostat.   This device, when the engine was cool, by-passed the oil cooler and warmed the oil up faster of course.   It is not binary... meaning just open or closed.   It regulates temperature and will actually maintain oil temp where it is supposed to be, usually even with the oil cooler door wide open.



At some point of time, there was a Russian directive, which I am sure you can find, that REMOVED these devices from the oil cooler.  The Russian logbooks for my 1985 YAK-50 show this as being done.   The result was that my oil cooler did not have the thermostat installed at all, and it took a very long time to warm up the oil in cold weather, just as this person is experiencing.  The thermostat itself is set to by-pass the oil cooler, and when it starts seeing warm oil, it then runs the oil THROUGH the oil cooler.   If it fails, it usually fails in the by-pass condition, which is... I think... why the Russians removed it.  It is failed in that position, it will cook the oil and possibly ruin the engine.   In any case, my oil cooler thermostat had been removed and so noted.



I obtained one of these thermostats/veritherms out of a Russian oil cooler for an M-14 helicopter and put it back into my YAK-50 oil cooler (easy job really) where it now operates perfectly.   I wrote all this up about a decade ago on the YAK list.



My guess is that he does not have a stuck thermostat, but that instead he has not got one installed at all.



Mark

--

apatton2

Joined: 17 Jan 2018
Posts: 32

Posted: Fri Jan 19, 2018 10:22 am Post subject: Re: Super-cool oil temp

Hi Mark,

Many thanks for your note. I will correspond with former owner and see if he can tell me anything about typical oil warmup time.



In the meantime, could you point me to any places to check for a thermostat as you suggest? Have written to Avioservice in BG as they have been a good resource for hard to find parts previously, but I've not yet heard back.

Many thanks!

Andrew

_________________
Andrew Patton
Yak-50
San Francisco, CA

mark.bitterlich(at)navy.m
Guest

Posted: Fri Jan 19, 2018 11:09 am Post subject: Super-cool oil temp

Andrew, it has been 10 years ... so my memory is not picture perfect.  But I do think you would have to remove the oil cooler to know for sure.  As I recall it screws into a hole, and we had to remove a screw in cover, and replace it with the thermostat part.   I am at work and do not have access to my manuals which MIGHT show it.   I'm afraid that is the best I can do.   The person who would know for sure would be Vladimir Yastremski.   He is up the street from you in Ramona CA.   Or down the street?  Whatever.

Mark

--

wlannon(at)shaw.ca
Guest

Posted: Fri Jan 19, 2018 11:11 am Post subject: Super-cool oil temp

Mark;



The same problem was addressed in the Canadian production of the North 

American Harvard (predecessor of the T6) to accommodate very cold winter 

operation.



A different method was used consisting of what they called a "surge valve" 

in the oil out line that opened whenever the scavenge pump pressure reached 

83 psi.

and directed oil to the tank rather than the oil cooler.

Scavenge pump pressure is not regulated so temperature is a major factor in 

oil out viscosity.  I suspect a thermostatic device would be more efficient 

but also far more subject to failure.



Walt



--

apatton2

Joined: 17 Jan 2018
Posts: 32

Posted: Fri Jan 19, 2018 7:16 pm Post subject: Re: Super-cool oil temp

Thanks much, Mark and co, for the further help. I got a picture of the thermovalve today (at least I'm pretty sure this is it).

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_________________
Andrew Patton
Yak-50
San Francisco, CA

Rob Rowe

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

Posted: Sat Jan 20, 2018 3:11 am Post subject: Re: Super-cool oil temp

Hi Andrew,



Like Mark I also fitted the original 'thermo(stat)-(safety)valve' back into my -52 in 2010 and it's reduced the engine warm-up time and more importantly got the oil temps into the green to boil off any corrosive moisture (mine's a cool engine in-flight).



I've attached an image of the two units with the thermo-valve (left) and pressure valve on the right.



Sourced the thermo-valve from a one-off surplus Mi-8 helicopter hydraulic inter-cooler in the UK (sometimes used for competition aircraft oil coolers). Given they made 17,000+ Mi-8s you would hope someone somewhere might have spares, but they seem to be like hen's teeth :-(



To follow on from Mark's thoughts ... the very cold weather SOP is to blow ducted hot air into the engine and oil cooler (see other image). 



However this causes the original fit cooler thermo-valve to open about 7mm max (it's just a simple expanding paraffin wax device with an over-pressure relief spring at the base) allowing oil through the cooler matrix.



Trouble is the upstream large oil pipes feeding the cooler are still full of unheated congealed (Russian) oil ... that then gets fed into the cooler matrix on engine start with the potential to rupture it.



Now the over-pressure spring in the base is supposed to take care of this and my conjecture is that the limited travel and force required in practice was not always enough to protect the cooler matrix in time. 



This is from having compared the operation of the thermo-valve versus the (field replacement) pressure relief valve and the latter takes less effort to operate (simply based on pushing down hard on both with my hand).



Presumably this is not  an issue for Mi-8 helicopter cooler usage as the viscosity of cold hydraulic oil is less than aircraft engine oils.



FWIW - I've experienced no issues using the thermo-valve on my -52 over the last 7 years using western oils, albeit in less extreme temperatures (UK is relatively mild). YMMV.



Brgds, Rob R

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Thermo-Valve (left) & Pressure Valve (right)

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apatton2

Joined: 17 Jan 2018
Posts: 32

Posted: Sat Jan 20, 2018 9:26 am Post subject: Re: Super-cool oil temp

Hi Mark,

Wow. Thanks for the pictures and the additional detail on the thermovalve. I'm still working on finding one. Our typical Northern California temps aren't that extreme, but agree that the thermovalve is a more ideal solution.



Very helpful to see the difference between the PRV and the thermovalve.

I'll keep looking.

Andrew

_________________
Andrew Patton
Yak-50
San Francisco, CA

apatton2

Joined: 17 Jan 2018
Posts: 32

Posted: Sat Jan 20, 2018 9:33 am Post subject: Re: Super-cool oil temp

Hi Mark - just a shot - do you have a part number for this valve?

Many thanks

Andrew

_________________
Andrew Patton
Yak-50
San Francisco, CA

richard.goode(at)russiana
Guest

Posted: Sun Jan 21, 2018 2:29 am Post subject: Super-cool oil temp

Andrew - for my interest, what would you do with a part number if you had

one? I don't know of anyone in this little business who catalogues anything

by part numbers!



Richard



Richard Goode Aerobatics

Rhodds Farm

Lyonshall

Hereford

HR5 3LW



Tel:  +44 (0) 1544 340120

Fax: +44 (0) 1544 340129

www.russianaeros.com

--

McFly

Joined: 21 May 2012
Posts: 101
Location: Scottsdale, AZ

Posted: Sun Jan 21, 2018 7:08 am Post subject: Super-cool oil temp

Doug Sapp does! 



Todd



Sent from my iPhone



[quote] On Jan 21, 2018, at 2:29 AM, Richard Goode <richard.goode(at)russianaeros.com> wrote:

 

 

 

 Andrew - for my interest, what would you do with a part number if you had

 one? I don't know of anyone in this little business who catalogues anything

 by part numbers!

 

 Richard

 

 Richard Goode Aerobatics

 Rhodds Farm

 Lyonshall

 Hereford

 HR5 3LW

 

 Tel:  +44 (0) 1544 340120

 Fax: +44 (0) 1544 340129

 www.russianaeros.com

 

 

 --

_________________
Todd McCutchan
Fast Aircraft
T-34A - N134FA
KDVT Hangar 33-13

Cell - 260.402.1740

Email: todd@fastaircraft.com
Skype: tmccutchan
Web: www.fastaircraft.com & www.flyams.com

apatton2

Joined: 17 Jan 2018
Posts: 32

Posted: Sun Jan 21, 2018 8:30 am Post subject: Re: Super-cool oil temp

Hi Richard - in the past it has helped to be able to google search things like this via p/n (especially if there were 20,000 made for Mi-17 helos). Worth a shot.

Best

Andrew

_________________
Andrew Patton
Yak-50
San Francisco, CA

dougsappllc(at)gmail.com
Guest

Posted: Sun Jan 21, 2018 10:15 am Post subject: Super-cool oil temp

Richard,Amen Todd!!

When I had only 3-400 line items (and was 50 years old) I did it by part name too, but now with over 2,000 line items (and 71 years old)

names don't seem to do the job very well any more.Â Â 

Doug



On Sun, Jan 21, 2018 at 2:29 AM, Richard Goode <richard.goode(at)russianaeros.com (richard.goode(at)russianaeros.com)> wrote:

[quote]--> Yak-List message posted by: "Richard Goode" <richard.goode(at)russianaeros.com (richard.goode(at)russianaeros.com)>

 

 Andrew - for my interest, what would you do with a part number if you had

 one? I don't know of anyone in this little business who catalogues anything

 by part numbers!

 

 Richard

 

 Richard Goode Aerobatics

 Rhodds Farm

 Lyonshall

 Hereford

 HR5 3LW

 

 Tel:Â  [url=tel:%2B44%20%280%29%201544%20340120]+44 (0) 1544 340120[/url]

 Fax: [url=tel:%2B44%20%280%29%201544%20340129]+44 (0) 1544 340129[/url]

 www.russianaeros.com

 

 

 --

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