Jab Motors and Pump Fuel

[Z-MRP]

Think this was discussed sometime back but here goes. There seems to be several conflicting idea's to using pump fuel instead of avgas in the jab motor.Some say yes but TBO reduced to 400hrs, others say pump fuel will burn a hole in the piston.Please can I have some expert advise so that next visit to the club we can put this issue to bed.We got 2 aries with jab motors and both up for sale as avgas very difficult to source now. I stand corrected but is it correct that in some countries you can use mogas and others not, why is this?

[Slabfish]

Look at this http://avcom.co.za/phpBB3/viewtopic.php ... b7449b21b2 discussion on Avcom .

[Mogas]

Ok here goes
Firstly you can use Mogas instead of Avgas but it must be of 95 octane rating.
TBO reduced by 400 hours? never heard of that.
Avgas has lead added to reduce the chances of detonation and the lead also lubricates valve seats. It was designed for use on old Lycomings and Continentals.
Really old engines can not use mogas if they do not have hardened valve seats, the Jabis all have hardened valve seats.
The newer Jabis also have re-profiled combustion chambers which make them less prone to detonation and more tolerant for the use of Mogas.
Another thing to consider is that mogas is more prone to vapor lock when the fuel is lifted under suction, is hot and at high altitude.
The short answer is this.
It is safer to use Avgas in your Jab but you are wasting money if:
You have access to clean/fresh 95RON mogas.
You are not sucking your fuel uphill.
You fly at normal altitudes.
Your fuel lines are heat sleeved where there is any exposure to a heat source like in the engine bay.
There is a lot of good info here on Avcom http://www.avcom.co.za/phpBB3/viewforum.php?f=59
Lots of high our operators use Mogas, including us at Kitplanes, just stick to the rules.
Mogas

[justin.schoeman]

Jabiru's notes on which engines, and which fuels are at the end of this doc...

http://www.jabiru.net.au/Jabachat/Jaba% ... 202010.pdf

[German]

Dont understand the lead lubricate the valves in afgas. Rotax state in their manual that if you use afgas you have to change oil more frequently and it may damage (more wear) the valve stems

[Z-MRP]

Thanks guys, think this puts to bed all the Q & A's .Mogas thanks for your simplified version.

[tandemtod1]

Lots of high our operators use Mogas, including us at Kitplanes, just stick to the rules.
MogasNottaquitta
Mogas
Top Gun


Posts: 594
Joined: Thu Jan 11, 2007 5:51 pm
Location: Nelspruit
Website

Who's rules are you going to stick to? The rule is simple, the aircraft manufacturer determines what fuel the aircraft should run on and usually with good reason. In order for you to run on anything different than what is laid down in the operators handbook, you require either authorisation from the manufacturer or the SACAA. If you don't have one or the other then you may not run your Jabi on mogas. Has anyone with a Jabi asked the manufacturer? and if so, what was their response? Several aircraft types in the USA that run with Lyc's and Conti's have been approved to run on Mogas but in order to do this, the FAA has required mods to the fuel system. These mods take the form of a primary or backup fuel pump with a restricted return line to the tank. Even if you have a high wing with the tanks in the wings, this mod is mandatory in order to preclude any possibility of fuel vaporisation. High fuel temperature is not the only way to vaporise fuel and create a vapour lock, altitude does it too!
So if you are going to run on mogas with a Jabi, then I don't think that the Q and A's have been put to bed, rather I think that you have just started them all over again. The manufacturer doesn't make these rules just to mess with you, he has your SAFETY uppermost in his mind. If you are going to ignore this and do your own thing just because someone on a public forum says you can, then your sense of self preservation is underdeveloped.
Stick to the rules my ass

[Duck Rogers]

Who's rules are you going to stick to? The rule is simple, the aircraft manufacturer determines what fuel the aircraft should run on and usually with good reason. In order for you to run on anything different than what is laid down in the operators handbook, you require either authorisation from the manufacturer or the SACAA. If you don't have one or the other then you may not run your Jabi on mogas. Has anyone with a Jabi asked the manufacturer? and if so, what was their response? Several aircraft types in the USA that run with Lyc's and Conti's have been approved to run on Mogas but in order to do this, the FAA has required mods to the fuel system. These mods take the form of a primary or backup fuel pump with a restricted return line to the tank. Even if you have a high wing with the tanks in the wings, this mod is mandatory in order to preclude any possibility of fuel vaporisation. High fuel temperature is not the only way to vaporise fuel and create a vapour lock, altitude does it too!
So if you are going to run on mogas with a Jabi, then I don't think that the Q and A's have been put to bed, rather I think that you have just started them all over again. The manufacturer doesn't make these rules just to mess with you, he has your SAFETY uppermost in his mind. If you are going to ignore this and do your own thing just because someone on a public forum says you can, then your sense of self preservation is underdeveloped.
Stick to the rules my ass

Dear Mr tandemtod1............please read the last 2 pages of the .pdf file referred to by justin.schoeman a few posts up from this.
After you have enlightened yourself, please be so kind as to point out to us uninformed, non-Engineers where, in the post by mogas, did he contradict the manufacturer? In fact, if I read it correctly he re-affirmed the "rules" of the manufacturer.

[tandemtod1]

Dear Mr. Duck Rodgers
My point was very badly made so you missed it. I think you also failed to pick up on the sarcasm. There was no critisism against Justin but it's very nice of you to defend him. It seems that the chemistry and physics regarding fuel vaporisation seem to have changed so I guess I'll have to go and re- enlighten myself and while I'm about it I think I must learn how to express myself like a simpleton so you can more easily follow in the future. You have a nice day now.

[Mogas]

Eish.......

[Mogas]

Who's rules are you going to stick to? The rule is simple, the aircraft manufacturer determines what fuel the aircraft should run on and usually with good reason. In order for you to run on anything different than what is laid down in the operators handbook, you require either authorisation from the manufacturer or the SACAA. If you don't have one or the other then you may not run your Jabi on mogas. Has anyone with a Jabi asked the manufacturer? and if so, what was their response? Several aircraft types in the USA that run with Lyc's and Conti's have been approved to run on Mogas but in order to do this, the FAA has required mods to the fuel system. These mods take the form of a primary or backup fuel pump with a restricted return line to the tank. Even if you have a high wing with the tanks in the wings, this mod is mandatory in order to preclude any possibility of fuel vaporisation. High fuel temperature is not the only way to vaporise fuel and create a vapour lock, altitude does it too!
So if you are going to run on mogas with a Jabi, then I don't think that the Q and A's have been put to bed, rather I think that you have just started them all over again. The manufacturer doesn't make these rules just to mess with you, he has your SAFETY uppermost in his mind. If you are going to ignore this and do your own thing just because someone on a public forum says you can, then your sense of self preservation is underdeveloped.
Stick to the rules my ass

Dear Mr tandemtod1............please read the last 2 pages of the .pdf file referred to by justin.schoeman a few posts up from this.
After you have enlightened yourself, please be so kind as to point out to us uninformed, non-Engineers where, in the post by mogas, did he contradict the manufacturer? In fact, if I read it correctly he re-affirmed the "rules" of the manufacturer.

Thanks for batting for me Duck, don't know what has got this dude so uptight
Anyway, lets put this one to bed.
Cheers
Mogas

[KFA]

From the Latest Jabiru news letter.:

What does Jabiru think of Automotive Fuel?
Generally, automotive fuel or MOGAS is good stuff. Our engine testing in recent years has
been done with a mixture of MOGAS for some tests and AVGAS for others and generally we
really like what we see in an engine using MOGAS. The problem is that the fuel you get from
the pump today is probably not going to be the same as you got last time or that you will get
next time. Cars have much more margin for error on fuel – they don’t care if the current tankfull
is old, stale, down a few Octane points and contains a few percent alcohol. Jabiru Engines
need more care because they are working much harder, running hotter and don’t have a computer
to monitor everything.
We have no objections to operators using MOGAS provided they are aware of these potential
issues. Again, more details were given in the Service Letter but the basics boil down to using
the freshest, highest Octane-rated fuel available, avoiding Octane Boosters where possible,
not storing it for long (especially in the aeroplane), keeping the electric boost pump turned ON
during critical modes of flight (to prevent vapour-lock) and checking its alcohol content

[Duck Rogers]

Anyway, lets put this one to bed

[Mogas]

Here is a simple test for alcohol (ethanol) in fuel, based on the principle that water will mix with alcohol but not with mineral based fuel.
Use a clear glass container.
Put some water in it, a tot or so.
Accurately mark the level where the top of the water is.
Add your fuel sample.
Shake well.
Allow to settle for a short time.
See if the water mark still lines up.
If it does not, some of the water has mixed with the alcohol and is in suspension in the fuel.
If the mark does line up, the water has not mixed and you can assume that there is no alcohol in the fuel.

[Morph]

Eish for a moment there I had to scroll back to the top of the page to see which forum I was on

Seriously, I think you are all right, just lost in translation that's all. I also feel it is getting increasingly important to give people accurate technical information, ala cleaning fuel filters and stuff.

Personally, unless I get a Technical Bulletin from Jabiru stating that engine numbers x to y can use Mogas under certain conditions and mine is one of those, I would rather err on the side of caution. IMHO

If you have your own pump bowser, and you can control the freshness and quality of your fuel, then by all means go ahead, but for me having to go to different garages, not knowing the quality of their fuel, etc, leaves too much to chance, especially if you are on a long trip.