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100LL engines - going nowhere? (why aren't more engines approved for 91UL?)

Having been in business for over 40 years, I suspect the main problems are

  • if you split the fuel purchasing, you (the airport) pay a higher price for the fuel, which partly or wholly negates the extra business from carrying the other fuel(s)
  • storage life may be limited (legally or practically) so it depends on how much business you get; note that GA activity almost collapses in the winter, in some areas

But we have done this before. I think Bosco made a good post above. It would be interesting to know why the FAA process has (almost?) ended. Maybe the different fuels proposed simply cannot be mixed? Maybe there were issues with fuel system components, but nondisclosure agreements prevent them coming out?

Administrator
Shoreham EGKA, United Kingdom

Storage of aviation fuel is no problem. It can be stored for years. When we used the Pawnee to tow gliders (100LL), one of the things I had to do as part of the daily checks in the morning, was to inspect the 100LL and Jet A1 facility. This meant, among other things, checking for water with some special paper stuff, and drain if found. I can’t remember ever having found a drop of water.

MOGAS on the other hand, must be handled as fresh vegetables. It starts deteriorating from day one. This means, you cannot have a big storage facility, it should be small and mobile, so the entire content is replaced every month or so on average.

What I mean is, if for whatever reason there is a problem having two or more different fuels on an airfield, then there really isn’t much hope of fixing anything at all. I can’t imagine that this is a problem anywhere but the UK. Getting fuel, handling it, distributing it, is easy and cheap. Anyone can do it. But making money selling fuel? When was the last time car gas station made money selling fuel? 30-40 years ago maybe. They make money selling burgers and chips, coffee and pastry, otherwise they are purely an end distributing point for the refineries.

The FAA is left with a very peculiar problem to solve. How do we replace 100LL with something unleaded so that a super tiny fraction of the population can continue flying 40-50 year old aircraft. No one in their right mind is putting effort into that. Politically that problem is dead. Silvair’s solution will solve it. Electronic ignition will solve it, FADEC will solve it. The problem is solvable in so many ways, it’s just pick and choose. Nothing is done because those who fly a lot use Jet A1, and the rest can do whatever they want with their ancient machines, but are too cheap to do anything.

The elephant is the circulation
ENVA ENOP ENMO, Norway

super tiny fraction of the population

Except… it is not. Might well be in Norway though, and some other parts of Europe.

MOGAS on the other hand, must be handled as fresh vegetables

Well, there you go. That may have been another reason for the issues with the FAA evaluation.

Another one was quite possibly licensing/patent issues; all the candidate vendors want to make money long-term, not just hand over their formula. The FAA is historically very unhappy with giving a commercial monopoly to somebody, via regulation which everybody has to comply with. It’s a distasteful thing to do. STCs are one such but one can argue there are other routes…

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

Except… it is not. Might well be in Norway though, and some other parts of Europe.

I was thinking of the entire population in a political perspective. For whom is 100LL important, and for which reasons? It’s all self evident isn’t it. Politically 100LL is a no issue, because so little is used of it. Politicians don’t care. Maybe some environmental activist group would care, I don’t know, but I imagine they have much bigger fishes to fry.

I Norway we hunt. In 2004 or something leaded gunshot pellets became illegal due to, well – lead. The problem was, no good alternative ever came up. Lead has a unique killing ability like no other metal (maybe except pure gold or uranium or some similar unobtainium?) First and foremost it’s birds you shoot with shotguns, and it’s important to kill the bird, not inflict injury and a long and painful death. A couple of years ago it became legal again, and no one has ever argued about it to my knowledge. The problem with lead here is purely a symbolic one. The concentration is way too low to have any effect whatsoever.

It’s the same with 100LL. It’s a symbolic problem. It’s a difference if one dude use the creek as a pissoar every now and then, and the entire town use it all the time, and not only as a pissoar. Poisson is measured in concentration.

The difference with 100LL compared with lead gunshots; there are solutions to the problem these are:

  • Turbine running Jet A1, solutions for 99.99% of all commercial aviation
  • Piston engine running Jet A1. Many in production today
  • UL91: Works for 90% of all old piston engines
  • Simple, true and tested mod : EI, Water injection etc
  • new tech: Electric, Hybrid
  • Some other additive the pilot can pour into the tank to fly his ancient craft.

It’s not really a problem, at least nobody care if it is or not. And if it is a problem, it’s already solved.

The elephant is the circulation
ENVA ENOP ENMO, Norway

LeSving wrote:

The problem with lead here is purely a symbolic one. The concentration is way too low to have any effect whatsoever.

I think that’s fairly obviously true, and it’s why the dance between EPA (which ‘protects’ the environment) and FAA can continue indefinitely. The reason FAA funds studies to find a drop in replacement is that it’s the no compromises solution and eventually it might work. There’s no great hurry in reality, just a hurry to talk and issue press releases.

Re two different aviation fuels, it wasn’t that long ago that I was fueling my plane with 80/87 and if there were an actual urgent problem I guarantee you we’d have 91UL in very short order. It’s certainly true that of the 700 aircraft resident at my home base many of them, and the ones that burn the most, can only burn 100LL but in the US there is still plenty of demand for both at many airports. It’s just easier to have only one fuel.

LeSving wrote:

In 2004 or something leaded gunshot pellets became illegal due to, well – lead.

A few years ago small motorcycles for kids were outlawed in my area, because toys can’t contain lead… including lead solder! In the end it was sorted out, aided in part by dealers who refused to comply. There is no limit to the ‘accidents’ that can happen when activist regulators are involved.

Last Edited by Silvaire at 07 Dec 16:13

Fly310 wrote:

UL91 is quite established in Sweden

Hjelmco 91/96UL is quite established, although I know there are some places with UL91. 91/96UL is not exactly the same as 91UL, e.g. Lycoming specifies that some engines can run on one and not the other (both ways).

ESKC (Uppsala/Sundbro), Sweden

MOGAS on the other hand, must be handled as fresh vegetables. It starts deteriorating from day one. This means, you cannot have a big storage facility, it should be small and mobile, so the entire content is replaced every month or so on average.

Can somebody justify this statement? If any gasoline (leaded or unleaded, for car or for planes, with any octane rating) contains no alcool, then has the same (unlimited) shelflife as far as I know.

United Kingdom

Maybe this i.e. more selective evaporation if there is any venting of the container, and AFAIK bowsers are vented.

Administrator
Shoreham EGKA, United Kingdom

Selective evaporation of lighter fractions should just improve anti-vapor-lock features of a gasoline. But I don’t have sufficient knowledge to say if that comes also with a detrimental change of octane rating (not sure if high octane is determined more by light or by heavy fractions in an unleaded gasoline). Good point.

United Kingdom

mancival wrote:

Can somebody justify this statement? If any gasoline (leaded or unleaded, for car or for planes, with any octane rating) contains no alcool, then has the same (unlimited) shelflife as far as I know.

The thing is (as far as I know) that mogas and avgas are two different concepts, rather than different products. Avgas is specified to keep it’s rather strict specification over long time storage, mogas is not. The only thing you can be sure of with mogas is the octane number at the time it’s filled from the gas station. What happens over time in storage is unknown, because the mix of hydrocarbons and any additive to achieve the octane rating at any given time, changes. UL91 or 91/96UL or whatever it’s called, is like mogas in a way, only all the unknowns are replaced with known (stable) quantities.

But in practice, I agree. What are the odds for the octane rating changing? Probably very very small.

The elephant is the circulation
ENVA ENOP ENMO, Norway
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