I think Ben Visser was spot on in his Sept. 7 piece, The definition of insanity, when he cites the old 80/20 rule regarding 100LL use. I believe it is indeed 20% of the GA fleet, the Navajos, the Barons, the Cessna 400 series, etc., that are burning 80% of the 100LL produced. But I also believe it’s this high end of the GA fleet that is being replaced by the Caravans, the TBM-850s, the PC-12s, etc., not to mention the coming VLJs.
As the high end users of 100LL move more and more to Jet A, I see the market for 100LL shrinking farther and farther, to where it becomes even more of a boutique fuel than it is today. For this reason alone, I think that 80% of the fleet that can burn unleaded fuel should start moving in that direction. There’s, what, one plant left in the world currently producing tetraethyl lead? A market is either growing or dying, and the market for TEL is not growing.
I would love to hear more about the Hjelmco 91/96 UL avgas, produced by Hjelmco Oil AB of Sweden. I understand that this fuel has been sold in Sweden for about seven years now and has been used by the Swedish Air Force since 1981. I also understand that Lars Hjelmberg, the founder and owner of Hjelmco Oil, uses it in his personal Navajo; and I understand that it’s the reason for Lycoming Service Instruction No. 1070L.
I would also like to hear more about the progress of GAMI’s PRISM ignition system. GAMI’s George Braly presented a forum at Oshkosh several years ago on the PRISM ignition system, and I remember being fascinated. The PRISM system that Braly showed was only an ignition system, not a FADEC system, but it did incorporate knock sensors. It looked like it could be relatively easily retrofitted to practically the entire piston fleet. According to Braly, GAMI took what they referred to as the most knock prone engine in the fleet, the Lycoming TIO 540, and got the rated 350 hp out of it using 91/96 UL — and with no knocking. Now I admit this may sound a little pie-in-the-sky, but it was being presented by a company with a rather well proven track record; albeit a company whose views, shall we say, are not always the most conventional.
JOHN MININGER
Quakertown, Pa.
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