If Lycoming is OK with it, I don’t see what the airframe maker could object about.
Alternatively in some POH, N-regged or not, I can read
Ҥ1.7 Fuel:
Minimum grade: AVGAS 100LL
Alternate grade: Refer to latest revision of Lyconental Service Bulletin Fuel and Grade oils”
Then the Lycoming SI1070V takes over officially.
Arne wrote:
If Lycoming is OK with it, I don’t see what the airframe maker could object about.
Alternatively in some POH, N-regged or not, I can read
Ҥ1.7 Fuel:
Minimum grade: AVGAS 100LL
Alternate grade: Refer to latest revision of Lyconental Service Bulletin Fuel and Grade oils”
Then the Lycoming SI1070V takes over officially.
Legally you can’t do it. In FAA land the airframe manufacturer is responsible and have to approve the fuel grade, until this is done 91UL is illegal to be used.
What is the probability that the Scottish farmer with his N-reg tractor will get caught at an FAA ramp check in his farm?
What is the probability of the fuel being mentioned in an accident report? The NTSB lists ALL N reg.accidents, wherever they occur, but does not investigate them. e.g. “Aircraft hit by roe deer when taxiing after landing”.
I think the practical answer to this will be: will your insurance company worm out of paying if you have an engine stoppage, cause some damage, and the fuel gets tested?
Well, all of this is hypothetical of course. Scottish farmers care desperately about the environment (except perhaps on November 5th when we will burn an effigy on a pile of old pallets, tractor tyres, feed sacks and used engine oil, not to mention a stack of fireworks). But none of us is going to risk upsetting Uncle Sam just so as to use a less-polluting fuel for mustering sheep in our bushplanes.
Incidentally, insurance underwriters rarely “worm” out of paying accident claims. It would be like a wine producer filling the occasional bottle with coloured water. Word would spread and people would stop buying it.
As for the regulators, well they’re smart people, worth every penny of their inflation-proofed pensions, but they’re going to struggle with any kind of enforcement action. I mean, you and I are pilots, so we know a thousand good reasons why changing nothing but the first letter of an aircraft’s registration number affects the safety and suitability of the fuel in its tanks. But to bring a prosecution, the FAA is going to have to convince a European NAA lawyer that he or she has a better than 50% chance of explaining this phenomenon to a magistrate. And a magistrate, or even a High Court judge, is very likely to be thick enough not to understand why two physically identical airplanes can’t use the same fuel.
Broadening the OP’s question slightly, who is using UL91 or 91/96UL on a regular basis, and what are the pros and cons? For instance:
Jacko wrote:
But to bring a prosecution, the FAA is going to have to convince a European NAA lawyer that he or she has a better than 50% chance of explaining this phenomenon to a magistrate
In cases like this, they’d simply revoke your FAA pilot certificate (if you have one) to make sure you can’t fly your N-registered plane in the US. See certificate action in the relevant AOPA link.
That aside, I think UL91 is legal for aircraft originally FAA certified on 80/87 minimum Avgas so if you had something with a 150 HP O-320 or other smaller Avgas engine, I think you’d be legal. The plugs would certainly benefit, just as with unleaded auto fuel on those engines.
Thanks Silvaire, I guess that “certificate action” might well follow in case “administrative action” was not considered to be appropriate.
But here’s another way of looking at the question:
In which respect would placing additional “Avgas UL 91” placards on the fuel caps and a corresponding supplement in the Flight Manual be considered other than a “minor change” according to 14 CFR 21.93 since it has “no appreciable effect on the weight, balance, structural strength, reliability, operational characteristics, or other characteristics affecting the airworthiness of the product” according to “acceptable” data (namely EASA’s CS-SC202b)?
If it is a “minor change”, no approval is required, just a logbook signature by an A&P.
Good day all,
I have noticed that the further north in Europe you go, the more prevalent UL91 appears to be – in fact there are some small aerodromes that dont sell 100LL, just 91LL.
So with that in mind, a few questions:
1. Where does one find out if an aeroplane can use 91UL instead of 100LL.
2. Are there any issues with mixing UL91 & 100LL in a tank? By which I mean arriving having used 100LL and filling up with UL91, then the reverse.
3. Are there any limits to using UL91 – such as the temperature issues with MoGas?
Regards, SD..
