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When will a diesel be available for my aircraft? |
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News, facts, and comments on the coming revolution for piston-engine aircraft.News of November 26, 2008Commenting on ExxonMobil decision to decline responsibility when Diesel Aircraft are fueled with Jet-A.As our subscribers know, in a letter sent by ExxonMobil US General Aviation Operations Manager Martin Tippl to distributors of Jet-A fuel on November 17, the company announced it has made the technical decision that ExxonMobil Aviation does not support or endorse the supply of jet fuel to aircraft powered by diesel engines. Included with the letter is an Indemnity Agreement, to be completed by suppliers and returned to ExxonMobil, prohibiting the supply of jet fuel to diesel-powered aircraft and releasing ExxonMobil from any liability in the matter. This is unclear: In other words can the client sign a discharge and refuel at his own risks, or is ExxonMobil directly forbidding suppliers to sell Jet-A to diesel aircraft? ExxonMobil details three technical reasons for its decision: • Ignition Quality- 'The fact that the minimum cetane required to establish airworthiness has not been determined, in combination with the fact that cetane is not measured as part of the jet fuel specification, means that ExxonMobil cannot guarantee the ignition performance of the jet fuel it supplies and cannot know if the aircraft will be airworthy after fueling.' Comment: What is ignition performance in a diesel engine applying spontaneous compression ignition? Does it mean that after all the work done by FAA since the late 90’s in certifying two diesel engines (Thielert and SMA) and after the world’s aviation experience in diesel aircraft going back to the 30’s, ExxonMobil has doubts about ignition taking place or not? Diesel ignition ability is famous for being extremely tolerant to nature of fuel (which doesn’t mean that any fuel can be used, for other reasons.) To pursue. • Freezing Point- 'Unlike turbine powered aircraft, piston powered aircraft do not reach speeds that cause heating of the fuel in the wing due to friction caused by airflow. It is therefore possible that an aircraft powered by a diesel engine could reach altitudes where the fuel would begin to freeze in flight.' Comment: This is a very good point in theory, which was the object of much investigation by FAA and others. Thielert’s answer was that warm excess fuel after combustion is recycled to the wing tanks, thus warming the unused fuel. Thielert on that point was proven right: None of the some 1,000 planes equipped with a Thielert ever reported such freezing incidents. SMA accepted to limit its STC to 12,500 ft until more experience would show that this is definitely a non-issue (182SMAs outside the US regularly fly above 12,500 ft.) • Lubricity- 'Diesel engines rely on the fuel to lubricate key components of the fuel injection system. ExxonMobil Aviation cannot guarantee that the lubricity performance of the jet fuel it supplies will meet the requirements of aviation diesel engines.' Comment: Wrong. Of course a diesel engine doesn’t rely on fuel as lubricant even though diesel fuel does have better lubricating qualities than gasoline. ExxonMobil states that 'until such time as the Federal Aviation Administration and the aviation fuel industry has a clearer idea of the full effects of these issues, the ExxonMobil Aviation position is that diesel powered aircraft should not be fueled with jet fuel.' Both the FAA and the industry having a practice of aero diesels have had a very clear idea of these issues for a long time. The letter using the word 'Until such time as' is where one smells of lawyers pushing ExxonMobil into taking restrictive precautions in fear of… in fear of what? The letter does not expressly state ExxonMobil will refuse to fuel diesel-powered aircraft... but does make clear that customers who insist on being fueled with Jet-A do so at their own risk. Customers insisting upon purchasing jet fuel for their diesel engine aircraft must sign an indemnity agreement before fueling. The letter concludes, 'No fueling of diesel engine aircraft with jet fuel may be performed without a valid indemnity agreement signed by the customer in place.' Comment: We read this as a warning to pilots in the US refueling with ExxonMobil that they should be ready to sign a discharge to the FBO selling the fuel (who is the customer) and forget about it. However there are very few diesel planes flying today in the US: less than 10 182SMAs (reporting zero incidents) and a few dozen DA42 (often grounded for other reasons.) Most aero diesels are flying in other countries. One thing for sure: ExxonMobil is inflicting a blow to Diamond Air, Thielert and also Austro Engine which might be fatal. It will also delay aero diesel in the US until one aircraft manufacturer obtains an STC for a product with a diesel as OEM. Today the next in line is the Maule M9-230 SMA. Our bet is that its certification will be the occasion for reestablishing the truth on this matter. Stay tuned. posted at 6:32 AM News of November 19, 2008A silence making a resounding noise...What is happening on the aero diesel front after so many major news recently? Officially, nothing. Under the surface, we can hear the rumor of major strategic negotiations. Fuel prices, after jumping sky-high (up to $6.70/gallon for Avgas in the US, much higher elsewhere), have come down, but may stabilize at relatively high levels: Petroleum will never be cheap again. Thielert and Diamond are certainly engaged in talks with possible buyers and partners who would help refinance a long term effort bringing to the market a water-cooled, in-line 4-stroke diesel pursuing their previous efforts. The total silence after so much noise indicates that Discovery and Due Diligence are in progress, probably with several negotiations going on at same time. Cirrus, Cessna and probably Piper are certainly reshuffling their long term market forecasts which have been shattered by the world economic recession now gaining in magnitude. The FAA and other international agencies need to address at same time the future of Avgas, the future of the huge fleet of old piston engined planes on the US registrar, and the growing needs of developing countries for economical workhorses in the 250-350HP range addressing urgent but professional applications: rescue, humanitarian, fire service, security, mini cargo, etc. They need to discuss whether Mogas can be finally a suitable alternative to Avgas, that would have some room besides diesels burning Jetfuel. Lycoming and Continental, officially, send 'business as usual' messages and conservative assessments such as: 'The situation is under control... We are preparing the best solutions for fuels available now... There is no need for a revolution, etc. while silently assessing what major innovative engine they will suddenly offer, and with whom. Business jets manufacturers may be wondering what kind of new tax code the new US Administration will impose, which might completely turn upside down the economics of owning a jet. Flight academies around the world must be thinking about the economics of a new generation of trainers offering 2 seats, a 100-120HP diesel and a fuel flow of 3 to 4 gallons/hour. But none of them is certified yet... In that context, which one is the event we are waiting eagerly? It will be Maule Air finally getting its Maule SMA diesel FAA certified. It will be the first market introduction for a certified airplane offering a certified diesel as OEM since the Diamond DA42. It will not amount to much in terms of units per year, but it will mean that there is one diesel engine for which FAA reconfirms an approval after the Thielert/Diamond crisis. It will accelerate many other decisions. posted at 9:36 AM |
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