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Mogas and the M14P (again!)

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psb777

Joined: 12 Aug 2009
Posts: 34
Location: UK

Posted: Thu Jul 22, 2010 2:36 am Post subject: Mogas and the M14P (again!)

This subject has been done to death, so it seems, and I think I have read much (maybe all) posted here about mogas in recent months.  Sorry to open it up again.



I am tempted to put mogas into my 18T.  I am currently in France and, as Didier reported in another thread, avgas is in short supply.  Certainly, here in the SE, no one is admitting to having any, and I have the last (so they said) from Cannes Mandelieu in my tanks.  Near me, at Gap-Tallard aerodrome, there is a mogas [MON/RON=88/97] pump and I am told there is no alcohol in that mogas.  Can I use it?  I think not.  [But please persuade me otherwise!]



The M14P Maintenance Manual says that the fuel must meet "B91/115 GOST  1012-72 octane rating at least 91".  



There are different definitions of octane rating.  According to my perhaps flawed reading in the West a 88/97 octane rating is MON=88, RON=97.  If a single figure is quoted this can be either but is usually the lower, the MON, or sometimes the AKI [the average(?) of the MON and RON].



Whatever, it does seem there is good reason to think 88/97 mogas is NOT good enough.  In the appendix of the manual B91/115 is explicitly stated to be MON=95.5 and RON=126.  There is also a much lower spec of fuel in the manual but UPON CAREFUL READING this is the spec of gasoline good enough merely to CLEAN the M14P!



On this forum I have read that our engines were designed for 70 octane. But I have read that only here.  Was that possibly for the very original non-supercharged designs?

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Paul Beardsell
G-PYAK http://beardsell.com/flying/g-pyak
Yak-18T http://beardsell.com/flying/yak18t

tigeryak18t

Joined: 26 Sep 2009
Posts: 233
Location: PARIS FRANCE

Posted: Thu Jul 22, 2010 2:33 pm Post subject: Mogas and the M14P (again!)

Paul,



just to reassure you, I spoke with Jan Mevis. He says that in Belgium they fly since long time with regular SP95 with ethanol. If you use it for a long time you will have some seal to change if ever but it will work fine. SP98 is better even if it is guaranteed max 5% ethanol, itseems that you can use it for the motors lifetime without noticing a difference only in your bank account. And on the lifetime of your motor the economy done will pay you a new motor.

  

I spoke also about that with Ricardas and Andrey. Both of them laugh at my question. They say that everybody in Spain, Italy, and the eastern countries run with MOGAS or sp95 or whatever they can pour in the tank without any problem. 

  

Then Bela also is running on MOGAS, ask him.



So I think you may fill your tank with MOGAS if you find some.



I am trying to provide MOGAS on my field but the petrol companies do not like that....t seems to be difficult.

  

If you have a contact at GAP/TALLARD I will be glad to phone him and ask who is his provider.



That said you are of coursethe only responsible of your flight.



I will run my plane with SP98 or better with MOGAS if I can.

  

If you are still in France tell me when you are near Paris and we will have a drink for sure this time.



PS : I am in holydays in Grece until 1st of august



kind regards



Didier



  2010/7/22 psb777 <matronics.com(at)beardsell.com>

 	  Quote: 	
		    --> Yak-List message posted by: "psb777" <matronics.com(at)beardsell.com>

 

 This subject has been done to death, so it seems, and I think I have read much (maybe all) posted here about mogas in recent months.  Sorry to open it up again.

 

 I am currently tempted to put mogas into my 18T.  I am currently in France and, as Didier reported in another thread, avgas is in short supply.  Certainly, here in the SE, no one is admitting to having any, and I have the last (so they said) from Cannes Mandelieu in my tanks.  Near me, at Gap-Tallard aerodrome, there is a mogas [MON/RON=88/97] pump and I am told there is no alcohol in that mogas.  Can I use it?  I think not.  [But please persuade me otherwise!]

   

 The M14P Maintenance Manual says that the fuel must meet "B91/115 GOST  1012-72 octane rating at least 91".

 

 There are different definitions of octane rating.  According to my perhaps flawed reading in the West a 88/97 octane rating is MON=88, RON=97.  If a single figure is quoted this can be either but is usually the lower, the MON, or sometimes the AKI [the average(?) of the MON and RON].

   

 Whatever, it does seem there is good reason to think 88/97 mogas is NOT good enough.  In the appendix of the manual B91/115 is explicitly stated to be MON=95.5 and RON=126.  There is also a much lower spec of fuel in the manual but UPON CAREFUL READING this is the spec of gasoline good enough merely to CLEAN the M14P!

   

 On this forum I have read that our engines were designed for 70 octane. But I have read that only here.  Was that possibly for the very original non-supercharged designs?

 

 --------

 Paul Beardsell

 HA-YAB http://beardsell.com/flying/ha-yab

 Yak-18T http://beardsell.com/flying/yak18t

 

 

 

 

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-- 

Didier BLOUZARD

didier.blouzard(at)gmail.com (didier.blouzard(at)gmail.com)

0624243672

  [quote][b]

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psb777

Joined: 12 Aug 2009
Posts: 34
Location: UK

Posted: Sun Jul 25, 2010 12:42 am Post subject: Re: Mogas and the M14P (again!)

Didier, thank you. 



The NOTAM saying there was no avgas at Gap-Tallard aerodrome expired yesterday and was not renewed.  Nevertheless, they still do not have any.



Yesterday I asked to see the specification of the mogas at Gap.  The last delivery, 14 July, had only 0.4% ethanol.  I topped up my tanks.  Currently I'm running on 2/3rd 100LL avgas and 1/3rd 87/98 mogas.  Seems to work!  All I have left to worry about is vapour lock during hot and high ops.  Today or tomorrow I'll pop over the 7200ft pass to Barcellonette, 3700ft.  And report back.  



Something for me to research - maybe someone here knows?  If I mix two liquids with different vapour pressures, does the resultant mixture have the lower of the two vapour pressures, or some intermediate average?

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jan.mevis(at)informavia.b
Guest

Posted: Sun Jul 25, 2010 9:50 am Post subject: Mogas and the M14P (again!)

Anyway, it is certain that AVGAS will dissapear, because it's not really

needed for business aviation, nor for the military. 

It will be ruled out because of the lead content. Maybe not immediately

forbidden, but only available at astronomical prices and/or very high taxes

so that flying a simple Cessna will become as expensive as is flying a P51D

today.

Jan



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