Avgas

[Russ]

School mate from many moons ago bumped into me the other day whilst holidaying here.........

 

he is employed with a major fuel company as a chemist.............within 10yrs there will be no LL100...............it will be pure unleaded.

 

Might cause heartache for some..........

 

 

[dazza 38]

Sound about right, from what i have read, on the net.Especialy in the states.I think there will be alot of STC'S coming along over the next few years.There are heaps already out there.A friend of mine works for caltex, at brisbane airport, says the same thing pretty much.Cheers

 

 

[airangel]

Ok Ok...Iwasnt going to ask but.'whats an STC?

 

 

[Cosmick]

Not sure, sounds like Jargon. I know what an STD is............. but not from personal experience.

 

 

[Bill Hamilton]

Folks,

 

An STC is a Supplementary Type Certificate ---- really only applicable to Certificated aircraft/engines.

 

There are already a number of (mostly US) companies that will sell you an STC to run various GA aircraft on motor fuel, but not the variety that contains Ethanol.

 

The "ethanol" problem is twofold, whether it is compatible with various seals, hose etc, and it "vapor pressure", which becomes a possible problem at altitude. I say "possible" problem, because I have done plenty of driving (in stinking hot, 35+ and freezing cold, -15) weather at 6-8,000 AMSL, without a problem - 10s of millions of cars do it every day in US.

 

If you have an old DH Gipsy engine, or other engines from the same period, have a look at the original Manufacturer's Manual ----it will say something like "Use a good grade of motor spirit, well filtered".To run on "leaded" fuel, they all had to have new cylinder heads, being originally designed to run on unleaded.

 

It was only the late and unlamented Australian Flight Manual that specified Avgas, where motor fuel would have been quite adequate.

 

Remember leaded fuel of any kind only became common during WW11.

 

Something like the Continental O-470 in all but the latest C-182 were originally certified on 80/87. Likewise all but the high horsepower Lycomings. In fact, all these older engines have a problem with lead fouling of the plugs, because they often don't run hot enough to properly scavenge all the lead.

 

My IO-470Ms were certified on 90/94, so either above should (from the octane point) run happily on premium unleaded motor fuel.

 

However, the "lead" has another important function, lubricating valve stems, particularly exhaust valves. Unless the engine (choice of materials) has been designed to run on "unleaded", you probably need to use a "lead substitute" additive.

 

From the RAOz point of view, things can be much more simple, as we are generally not using certified engines, all else being equal, switching to motor fuel does not have all the certification impediments --- not difficult, but horribly costly.

 

Depending on what engine you have right now, consider carefully whether you need Avgas -- but do your homework very carefully.

 

The impending loss of leaded fuel (more a commercial/economic problem, than an environmental problem -- there is so little avgas consumed it's enviro. impact is negligible but there is now only one single producer of tetra ethyl lead) is a much greater problem for high HP GA engines.

 

Regards

 

 

[Guest eland2705]

About 6 years back the wife and I were still riding "older" motorcycles (Honda CX500s) that were supposed to run on leaded fuel.

 

Because we rode all over Victoria, so we were never sure of the fuels that were available, we used an additive (blowed if I can remember it's name though) that we added so many ml per litre of unleaded. After 30 000 kms I had to lift the head on the wife's bike (for other reasons) and found that the piston rings and valves were in excellent heath, well for a 25 year old bike with 125 000 on the clock.

 

Is this additive a viable option in aviation, or are there rules and reg that preclude this practice?

 

 

[REastwood]

Something like the Continental O-470 in all but the latest C-182 were originally certified on 80/87. Likewise all but the high horsepower Lycomings. In fact, all these older engines have a problem with lead fouling of the plugs, because they often don't run hot enough to properly scavenge all the lead.

My IO-470Ms were certified on 90/94, so either above should (from the octane point) run happily on premium unleaded motor fuel.

Bill, are those numbers MON (Motor Octane Rating) or RON (Research Octane Rating)? There is quite a difference between the two. AVGAS is MON, so 100LL is (roughly) about 115 or so RON (maybe higher, I haven't got the figures here), where Premium Unleaded 95 is RON, so about 85 or so MON.

 

The main reason for engines like the Jabiru needing a higher octane rating than their compression suggests is the slow burn characteristics, i.e. a low octane give a short bang while a higher octane gives a long bang, putting less stress on crankshafts etc.

 

Rick.

 

 

[sain]

The other problem with ethanol as a fuel is its vapours are acidic, so it tends to corrode fuel tanks and other components more than unleaded does.

 

 

[jetjr]

One of the key issues with Mogas, I think, is the short storage life

 

It would be pretty common to have an aircraft full of fuel sit still for a month Id have thought and unleaded degrades significantly over this time.

 

I have an old Holden V8, been running it on Premium and additive - runs OK but let fuel sit for a while and its hopeless. Even with fresh fuel had to change timing and mixtures.

 

Had to use up some drained Avgas once, and it was a different engine, started, ran, performed beautifully. Older Premium even with additive isnt close to same performance. Serious ramifications in aircraft.

 

High use aircraft in major centres this may not be an issue but regional airports storage times would be longer.

 

 

[nomadpete]

AVGAS or MOGAS

 

Gents,

 

You have discussed the main (and very important) issues from the perspective of the motor. But what about the fuel tank? As soon as you put MOGAS into a fiberglass fuel tank there is the possibility of getting a batch of MOGAS which has some ETHANOL in it. From presonal experience, I can assure you that although I always purchased Premium unleaded for my ROTAX, the day came when my (factory built) fuel tanks developed pinholes in them. They had been fine for the first 13 years of use. Either they had a slow degredation, or they had a recent contamination of something not compatible with the resin. I vote for the Ethanol being the cause. Even the latest "Ethanol resistant" epoxies are subject to loss of strength when exposed to E10 fuel. I have serious concerns about the fuel tank issue since there are many aircraft with composite tanks.

 

PeterT

 

 

[Guest ozzie]

There has been some talk about avgas being phased out(legislated out) of the US. once this happens the rest of the world will follow quick smart as the biggest slice of the market has dried up. so why make it. plenty to read and listen to on the subject at the eaa sites. big thing at the moment is what they will have to replace it with that has no lead and won't kill all the dinosauruses engines.

 

never liked fibreglass tanks and never will.

 

 

[Russ]

When we lived "NT" i used to have fuel drops (20L) drums stashed all around the country side

 

( old disused strips all over the place ).............same mate told me always store me drums upside down........seals the lids, stops gradual air intake into the fuel, which degrades the fuel.

 

Also said if my engine ever showed "hard to start" .........you could generally put it down to degraded fuel ( the good stuff in the fuel is the first to deminish )

 

Also said this ethonol push is all wrong, but is pushed by canberra and thems folks.

 

Also be aware "NT" is becoming more and more where unleaded and the like, is only available from servos.........remote fuels are "opal", specially formulated so "persons" are unable to sniff it to get off their faces.........it also has a low octane rating.

 

remote communities are compelled to have avgas limited, and under lock and key. Unleaded is forbidden........period. Be aware.

 

Getting permission to once off have premium delivered for your transiting through, is entering into a mine field...........can be achieved, sometimes.........but rarely.

 

 

[Guest basscheffers]

100LL, what's that? Must be something you guys keep to yourself in the eastern states! We have to make do with the green 100/130 crap...

 

Remember that it is not just being taken away, there is work being done on many possible alternatives; you won't need to run MOGAS. The alternatives will have long shelf life and many of the other properties that leaded AVGAS has that is especially important for high-compression engines. (i.e.: not most of us)

 

And at the same time engine and aircraft manufacturers will be working on STCs for the new fuel and possibly engine mods. So if you have an older aircraft of which a fair few are still flying in the US there isn't a whole lot of you'll need to do yourself.

 

Though of course, this is Australia and I have no doubt of all the alternatives being developed, we'll try to be ahead of the game and choose one before the US does, with the US choosing a different one and us being stuffed. (*cough* ADS-B *cough*)

 

 

[Guest ozzie]

EAA News - Stakeholders Call for FAA-led Process on AvGas Replacement

[Guest milton56]

Question, What is the shelf life of Mogas?

 

 

[Russ]

Couple of yrs back my then machine was powered by a soob ej22 efi.........loved it, was alerted to problems running it on 100LL ( avgas )

 

contacted soob technical devision...................no probs russ, but not for too long, a tankfull no probs, then back onto unleaded.

 

Later.................

 

Was put onto an aditive by another guy, running efi engine on avgas most of the time, the product is "Decalin" via aircraft spruce, cheap as, easy to get. use as per directions, it scavenges the lead out, whatever, no soiling of oxygen sensors by the lead, a noticing of a white sootish in your exhaust is the tailtale sign it's working. I used this decalin for quite some time thereafter, as needed, never had efi problems.

 

Might interest some here.............

 

 

[Vev]

Hi Russ,

 

Your comment about Opal Fuel being low octane fuel is quite incorrect ... Opal is very high Octane ULP fuel at around 100 RON.

 

Cheers

 

Jack

 

 

[Russ]

G'day there jack................my understanding opal is in fact 91 octane. I just googled to be absolutely sure, just in case i was wrong................( wouldn't be the 1st time )

 

 

[Vev]

Hi Russ,

 

 

What you would have Googled was the Oil Company “Marketing” spec which is a claim in terms of a minimum octane, which is 91 RON to meet the ULP legal requirement… this spec doesn’t limit Octane above a legal min spec.

 

 

The reality is… Opal fuel can’t be sniffed because it is made from an extremely low aromatic hydrocarbon (low volatility) called Iso-Octane, which is the base product they make Avgas. In fact Opal is Avgas without the lead and has a RON of 100 and is the highest octane fuel form a service station possible.

 

 

It’s all in the detail and you need to go beyond the "marketing" spec and look at the actual chemistry …. Hope that explains things a little better.

 

 

Cheers

 

Jack

 

 

[bones]

Hi Russ,What you would have Googled was the Oil Company “Marketing” spec which is a claim in terms of a minimum octane, which is 91 RON to meet the ULP legal requirement… this spec doesn’t limit Octane above a legal min spec.

 

The reality is… Opal fuel can’t be sniffed because it is made from an extremely low aromatic hydrocarbon (low volatility) called Iso-Octane, which is the base product they make Avgas. In fact Opal is Avgas without the lead and has a RON of 100 and is the highest octane fuel form a service station possible.

 

It’s all in the detail and you need to go beyond the "marketing" spec and look at the actual chemistry …. Hope that explains things a little better.

 

Cheers

 

Jack

I just got back from 2 months over the NT and the opal is on the decline already, too many cars failing due to it, and the opal is worse for sniffing than the normal, the resourseful "people" in the area found a very simple and common additive to give them a better hit.

believe it or not they break up a bit of bitumen, put it in a cup and the fumes off that arrrrrr.

 

 

[Guest Maj Millard]

Hmmmm indeed....Bones, I heard the 'latest' for sniffing pleasure was Battery acid !!....Get that into those sinuses first thing in the morning........................................Maj...

 

 

[Vev]

Hi Bone,

 

Under the right conditions (which I won't explain) bitumen could easily kill someone siniffing it.... I really hope this doesn't catch on.

 

I'm not sure if I understand your statement correctly, but I do not believe that Opal is worse for sniffing, which I might add is tracked very well by health authorities and reported quaterly since 2005... the reports show a >75% reduction in related petrol sniffing problems as the components that make you high are at such a low levels it makes it very hard to get a hit from it.

 

However I an interested to hear your view on the causes of auto engine failures due to Opal fuel, but might be best to leave this at the risk of going off topic.

 

Cheers

 

Jack

 

 

[Bill Hamilton]

Bass,

 

The is little/no difference, operationally, between 100LL and 100/130. Interestingly, depending on the refinery, 100/130 may have less lead than 100LL.

 

There are now, as far as I am aware, only two sources of "avgas" in Australia, Shell Corio and BP Kwinana, so the name on the tanker/bowser doesn't mean much ( it never did), and the geographic distribution from each refinery is not "obviously logical".

 

Both sources of fuel ( and that imported from Indonesia and Singapore) meet the ASTM specification for Avgas, ASTM D 910 or DERD 2485, the testing method is in the specification, and involved measuring the octane at two different fuel air ratios, translate in "round engine speak" as the fuel air ratios for auto rich and auto lean (P&W) or rich and normal ( Curtis/ Wright).

 

Some interesting info:

 

<http://www.astm.org/SEARCH/sitesearch.html?>

 

<http://www.docstoc.com/docs/7671746/ASTM-D-910-%28Grades-Avgas-100-and-Avgas-100LL%29>

 

<http://www.shell.com/home/content/aviation/aeroshell/technical_talk/techart12_30071515.html>

 

The answer to RON, MON and avgas is all on the last address, a Shell page on the subject.

 

Regards,

 

 

[Russ]

Hi Mr Cook,

 

The Octane rating for Bp opal fuel is 91.

 

Kind Regards,

 

Elena.

 

Administration Officer - Fuels

 

BP Customer Response

 

1300 1300 27

 

www.bp.com.au

 

I'm scratchin me head here...........:confused::confused:

 

 

[Guest davidh10]

Bill;

 

Thanks for the info and links. Although I only use ULP (Mogas), it is all interesting and I hadn't heard of MON till it was mentioned in this thread.

 

Regards

 

David.