News, facts, and comments on the coming revolution for piston-engine aircraft.
In 1998, one diesel engine flew on a converted airplane for the first time since 1945. Today, close to 4,000 singles and twins are flying. This is the beginning of a worldwide trend which will eventually allow a rebirth of the piston-engined aircraft, around new specs and new missions.
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News of August 22, 2007
Oshkosh season: Of Facts and Rumors around the Diamond Air family of diesel aircraft. Part Three
We continue our story with the interview of Christian Dries CEO of Diamond Air, and our conclusions.
Christian Dries (CD) agreed with most of the facts as stated by Diamond customers, and stated that Diamond was now very active at proposing solutions to British and French operators. But, to answer Frank Thielert, he also added:
CD: 'The main problem is that Thielert is dramatically late in delivering spare parts. I agree that most of the time a quick replacement of a faulty spare part or of a part coming at TBO prevents grounding the plane and eliminates any potential crisis. A typical recurring case is the gearbox. Such delays were, in my opinion, a consequence of Thielert financial problems, which were solved only recently through a capital increase as you mention. Meanwhile, backlog of spare parts requests, and also of new engines, has been building up; it will now take quite some time to absorb it: After several rescheduling of deliveries Thielert is right now (August 07) again late on delivery of engines on order. At this time, Diamond is compelled to impose an unacceptable waiting list to any potential buyer of a new diesel aircraft. We have seen this problem building up as sales were growing: We have produced 480 twins, and are now producing 220 twins per year despite such delays, and could do more. This is the main reason why we are investing in our own engine factory and developing our own engines at least as an engine option that can be retrofitted on older Thielert equipped planes.'
CD also says: 'I believe that the main reason why you do not hear reports from Cessna 172 or Piper Warrior owners is because they often are isolated private pilots flying their own planes with very low flying times, so they run into the same kind of problem much later; also one can expect that they do not react as fast as a flight academy which has several aircraft grounded and cannot service its own students. I do report that there were two cases of a broken propeller shaft, fortunately with no dramatic consequences and I have available all accident data if requested. The latest engine defect reported to us was two months ago: a hole in a piston, in Germany.'
We asked Christian Dries what action was planned to satisfy present customers. He says: 'We are indeed negotiating right now with individual operators and with one British group jointly with Thielert and I follow these talks personally. We are determined to find a mutually satisfactory solution. But meanwhile we must plan our own future so as to avoid such situations.'
Regarding the new engine project and its certification:
CD: 'The engine is derived from a 2 liter (122 c. i.) Mercedes Benz block, so that we started the same way than Thielert did. But our technical options are very different: Ours delivers at least 170HP (176 with autodiesel fuel). Our cylinder head and combustion chamber design are different. Our injection pump system, same as Thielert, uses high pressure and Common Rail but that is the sole similarity: Our design is entirely new. We accepted a higher weight than Thielert (around 80 Lbs.) but our more efficient combustion allows not only for more power (170HP instead of 135) but also for 20% less specific fuel consumption than with the Thielert engine, which means that we can ultimately save 33 Lbs. on payload for the maximal range allowed on the old version, while flying faster. We confidently expect that the maximal take-off weight will be increased by 100 Lbs for the DA 40 and 160 Lbs for the DA42 so that overall performance will be superior.
Our gearbox design is completely new: We eliminated the risk that the FADEC system would shut down both engines in any emergency thanks to an independent constant speed prop monitor activated by its own stepping motor. Our engine delivers 100% nominal power up to 12,000 ft and 90% up to 18,000 ft, meaning we confidently expect a maximal cruise speed of 170 knots on the DA 40 and 200 on the DA 42. The engine is flying now on a DA40 prototype, and the DA42 version will fly in September. Our DA50 light version will use the same engine. And the main point is that, even though our main goal is to OEM our engine on our planes, we can also retrofit our new engine on any Diamond diesel aircraft produced since the origin.'
On the certification process, CD says: 'The EASA (European) certification process is running since 06. We foresee that by May 08 we should be ready, with the US FAA certification following shortly afterwards.'
Frank Thielert had an occasion to answer these statements. He recognized that there have been some delay problems, but not to the extent stated here; that many of them are due to a lack of reliable delivery schedule agreed between vendor and customer, and that deliveries are disrupted by last minute changes or new requests. All these sound very familiar in a situation in which a new family of products (the Diamond range) offering many innovations and meeting with success on the market, depend on a component technology (Thielert engine) which is innovative in nature.
Conclusions: It seems to me that both Diamond Air and Thielert Motoren are victims of success:
After decades of incubation, the aerodiesel market has suddenly taken off, backlogs have built up, and early bugs, unavoidable in any new engineering design, have provoked a fast build up of service problems. Delays in addressing them have turned minor incidents into horror stories.
All parties, even disgruntled customers, agree on many issues, which mean a brilliant future for aerodiesels.
Diesel aircraft is here to stay. There is no other alternative if the private branch of piston engined, small aircraft in General Aviation is to develop again and address new needs worldwide, especially in countries which are dependent on General Aviation as basic service.
Thielert is a pioneer, and ran into minor design problems, none of which put in question its basic concept. We can expect that by now all of them have a solution that can be retrofitted on all their engines. These problems have provoked customer service crises. We could expect that, in such a situation, a dispute would flare between Diamond and Thielert because we know by experience that tracing a technical bug to its fundamental cause is tricky, and when working under emergency conditions the component vendor and the OEM product manufacturer will find numerous occasions to put in good faith the blame on the other party; this all the more that disputes of that nature are discussed by design engineers who are among the most stubborn people in the world when trying to make their point.
Diamond attempt in developing an engine seems realistic, with a question mark on weight per HP, as always with new engines. If Diamond does succeed in developing their range of engines that can be retrofitted to older products, does offer better performance and does obtain certifications soon, one could hope that this effort will either mean than another engine vendor become available, or that an agreement will be found at a later date with Thielert reconsolidating production. However we see a major setback: How will Cirrus, Cessna and Piper accept to deal with Diamond Motors as an alternative to Thielert when Diamond is becoming a full-size competitor on their most sensitive markets? And in such a case I donâ€™t see how Diamond Motors can survive as a captive manufacturer with Diamond Air as sole customer.
Both Diamond Air and Thielert Motoren act like serious, committed manufacturers which are here to stay. We can imagine many customers dissatisfaction right now, but also recognize that both firms talk responsibly and make sense in their plans to satisfy the market.
Both Thielert and Diamond engines are In-Line, liquid cooled, geared engines. The context of this dispute will give ammunition to engine manufacturers offering non-geared, Opposite Piston, air/oil cooled engines, or offering 2-stroke engines. So the field remains open. After all, the two fastest piston engine airplanes ever made, and the most successful WW2 fighter planes, were already illustrating a competition between air-cooled, no gear, radial engines; and liquid cooled, geared, in-line ones. As well, the most fuel efficient piston engines ever made, the diesel Junkers Jumo, were 2-stroke diesels.
The aerodiesel market still is in infancy. All competitors are making progress. Limitations imposed by certifications will gradually be lifted. Thielert will be allowed to increase TBOs. SMA will be allowed to fly higher than 12,500 ft and will increase its power. DeltaHawk will demonstrate that a 2-stroke engine can offer a serious TBO. More profitable market niche situations will be discovered for retrofits. Etc.
Andre Teissier du Cros, DieselAir Newsletter, August 07.
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Every month: news, facts, and comments on the coming revolution for piston-engines aircrafts between 130 and 400 HP: Retrofitting a diesel engine to run on Jetfuel or Kerosene, reduce Gallons/Hour by some 30%, eliminate ignition systems (magnetos, spark plugs) and their problems, eliminate mixture control, increase TBO to 2,400-3,000 hours, increase performance between 6,000 and 12,500 ft., and drastically reduce Operating Costs.
The letter is intended for piston engines aircraft owners, manufacturers, fleet operators and FBOs, re-manufacturers of engines for these aircrafts, manufacturers of engine components and ancillaries, and all professionals acting in decisions of engine exchange or refitting at TBO, in North and South America, Pacific Rim, African continent, and all parts of the world were Avgas, Mogas, Kerosene and Jetfuel are available.
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