A Q&A with Lycoming’s top man

After Oshkosh, I sent an email to Michael Kraft, Lycoming’s senior vice president and general manager. Due to this busy travel schedule, he was just able to get his answers to me. To honor his request, I agreed to run this in a Q&A format.

Q: Is Lycoming working on or considering development of a diesel cycle piston aircraft engine?

Michael Kraft

Michael Kraft

A: It is public knowledge that Lycoming has had several Diesel cycle aviation engine development projects. These engines are certainly feasible; however, the open questions are quite frankly (a) consumer acceptance, (b) whether or not we could ever see a return on investment for certification of these products and (c) whether the turbine fuel supply globally is going to be suitable for diesel cycle operations on an aircraft.

There certainly is consumer interest in these types of power plants, but it remains to be seen whether consumers maintain their interest once the total life cycle costs are known. It’s a difficult tradeoff in North America where, no matter how you slice it, our fuel cost and the disparity between turbine and piston fuel is much lower than just about anywhere else in the world.

A: About six or seven years ago a Lycoming representative stated at an ASTM meeting that Lycoming must have a 100 octane unleaded fuel as a replacement for 100LL — that Lycoming could not operate existing engines or future engines on anything less.

A: The above misrepresents Lycoming’s statements and viewpoint on this subject. What we have repeatedly tried to communicate is that the existing fleet of aircraft, including some current production aircraft, has been certified around ASTM D910 100LL performance. If a 100LL substitute is not available, you will have a significant number of aircraft de-rated, if not grounded. By “fleet” we mean the global fleet, not just the aircraft in the United States. It is not a statement about Lycoming’s existing or future engines; this concern is echoed by a large number of user groups, the “Clean 100,” and the “Avgas Coalition.”

Lycoming’s position remains that we as an industry need an unleaded aviation gasoline solution for the fleet that is currently designed around 100LL. Once again, this is not a statement about Lycoming’s current or future engines, it’s a statement made in the context that there is a system out there supporting more than 200,000 aircraft with an average age of 30-plus years. You cannot ignore the installed base.

Q: Or will all future engines be designed to run on, say, a 94 octane unleaded fuel?

Q: All engines being produced today or being developed by Lycoming are not dependent on ASTM 100LL leaded avgas. We’ve made the materials changes years ago to accommodate unleaded fuels. Quite frankly we’re excited about the maintenance and longevity benefits of removing lead from the system. We’ve also taken steps in revisions to our SI1070 to ensure that our engines are approved on the widest variety of fuels available with the minimum octane demand clearly stated.

Q: What is your best guess as to what the future aviation gasoline will be?

A: It does not take much to guess on this one. If you look at developments globally: In some markets ASTM D 7547 UL91 unleaded avgas is already in production and distribution; in others high grade automotive gasoline is available and there are multiple technical solutions towards an 100LL unleaded equivalent. How many arrive to be available to the consumer broadly is largely going to be up to fuel production and distribution chain considerations. Lycoming’s “guess” is that the end solution will probably arrive at two unleaded grades — a universally suitable 100LL replacement and a “low octane” unleaded solution that might be effective for niche areas.

Q: The big question: What will Lycoming do with the existing fleet of engines?

A: Lycoming is not going to abandon the existing fleet of engines. As stated previously, we’re already taking measures to ensure compatibility with a wide range of fuels. The question is very open-ended, and what you can do is really dependent on engine octane demand and fuel availability.

Q: Will they need to be replaced or will systems and parts be available to re-certify these engines on another fuel?

A: For the majority of Lycoming engine models, no action will be required given the possible fuel outcomes. The engine is much less susceptible than the aircraft with respect to materials compatibility, so it’s unlikely that there will be big changes required in this respect.

Once again, Lycoming is not going to abandon the existing fleet of engines, and we’ll make certain we have a path forward. People need to realize that we cannot change the laws of physics either — which means if the engine octane demand is higher than the fuel, a de-rate will be necessary.

Q: Will Lycoming be certifying any engines on auto fuel? If so, how will you deal with the ethanol problem?

A: Lycoming has already certified engines for use on automotive gasoline. Our Service Instruction 1070, in fact, provides the ordering instructions that ASTM D 4814 prescribes for fuel distribution. Dealing with the “ethanol problem” is far broader than an engine discussion. Ethanol inclusion is a mandate for fuels used on roadways supported by state and federal tax dollars. Off-road fuels do not have mandates to include ethanol.

Q: Will electronic controls, knock sensors and other high tech systems be part of the next generations of Lycoming engines?

A: They already are, and the first applications of this technology, Lycoming’s “iE2,” may be found on the Lancair Evolution and the Northrop-Grumman Firebird. Both of those applications use high power density engines.

Lower power density (note that we’re not saying turbo and non-turbo here…) engines do not require all the bells and whistles. In fact, our parallel valve carbureted engines do quite well on just about anything you can throw at them — it’s hard to beat the combination of man and machine in those cases.


  1. Mack says

    “In fact, our parallel valve carbureted engines do quite well on just about anything you can throw at them”

    Okay, my O540-B4B5 works just great on mogas, funny how the Europeans call 91UL “perfumed mogas”!

    All this means absolutley nothing to me, I’ve been using mogas for 25 years with no ill-effects. It’s as confusing as New World Order, Obama, spoiled “athletes” coming out of the closet, and funding Chechnyan muslims to bomb us.

    “Beam me up, Scotty!”

    Actually, I just “levitate” in my Piper, and don’t worry about it!

  2. Kent Misegades says


    The dream of a single, drop-in replacement for 100LL is now finally dead.

    Future Lycomings will operate on a lower octane unleaded fuel, some call it mogas.

    No Jet-A diesels for now, despite Continental and many other offerings today.

    UL91 acceptable, but judging from Europe is not popular since mogas works and is cheap.

    Mr. Kraft is still confusing mogas from the pump with aviation-grade mogas at the terminal, where ethanol is first mixed. Two different animals.

    A clear endorsement from Lycoming for mogas – yea and no.

    Thanks Ben

  3. drew says

    any chance you will certify the O233 as a drop in replacement for the O235 L2C. after all it is faster ( more fuel eff and diverse fuels compliant) better ( electronic ignition ) and $8000 cheaper than the 25000 c152 be77 pa32 engines needing replacement. surely the faa would approve quicker given sequestration.

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