UL 91 Avgas

[BatMaule]

I missed this earlier in the year. http://www.generalaviationnews.com/2012 ... ded-avgas/. Notable is that all the engines for the 235 hp Maules and possibly the 260hp (V series) are going to be included. (The 360 series were already covered.)

"The latest models to be approved include the large installed base of (I)O- 320-B, D; LIO-320-B; O-540-A, D, E, F, G, H, J; and IO-540-C, D, N, T, V, W, AF, AB engine models"

An almost comical statement from the Lycoming spokesperson; "If your engine is approved on this fuel then your airframe is automatically approved ... in the EU. In the U.S., if the engine is approved, you may still need approval for the airframe."

A bit of common sense prevailing in the US and not Europe for a change.

SO...where and when does someone go about buying ASTM D7547 UL 91 unleaded avgas in the US. Looks like it is on market in the EU. Just have to make sure your airframe is approved. As far as I know it isn't available in the US yet. Anyone know differently?

[Njacko]

Resurrecting this old thread, I'm thinking of switching to UL91 for the next fill of my fuel bowser. Reason: I guess just cleaner plugs and oil.

My O-360-C1F is approved by Lycoming for this fuel, but the (US registered) airframe is not. However, an identical EASA registered MX-7-180 would be automatically approved on the basis of the engine approval and this kind of issue might even be part of the FAA/EASA bilateral agreements. So for an N-Reg Maule operating in Europe, it's a bit of a grey area.

Does the Maule factory have any plans (or even the authority) to issue airplane-level approval to use UL91 (or 91/96UL)?

[DeltaRomeo]

Why does the airframe have to qualify for the new unleaded aviation fuels? If there is no ethanol etc in the fuel it should be compliant for the airframe as 100LL. The additives in mogas are a threat to the rubber in our 35 year old airframes, I get that. But the new unleaded fuels targeted to that vintage fleet should be engineered to meet the vintage fleet requirements. Its the whole reason that unleaded has yet to make it to the marketplace; being retroactively suitable. The only thing that is left to consider is a suitable additive that will perform the job that TEL did for the valve seats. Best I can tell, Lycoming has been using hardened valve seats since the 70's as part of the seat recession solution. Auto engine manufacturers did the same thing when TEL was removed from fuel and we are not seeing seat recession issues there. If anything, auto engines are lasting 2x longer or more since the removal of TEL, using electronic ignition, and fuel injection.

[Njacko]

Why does the airframe have to qualify for the new unleaded aviation fuels?

I can only guess why, but Lycoming does put it in capital letters in their latest version SI 1070V https://www.lycoming.com/sites/default/ ... uels_0.pdf : "AIRFRAME APPROVAL IS NECESSARY".

I suppose that there may be some genuine "airframe" considerations, for instance adequacy of engine cooling and/or CHT instrumentation, which could affect the likelyhood of a pre-ignition or detonation event.

However the EU regulator (EASA) has said "nuts" to that argument; hence I'm wondering aloud what the Maule factory's view is (if any).