Aerodiesels: Progress, If Not Thriving
Jet-A burning diesel aeroengines, we're led to believe, are the future of general aviation propulsion. So at Aero last week, I expected the place to be lousy with them. Well, not quite. There were a couple of new ones—SMA's six-cylinder concept engine and the nice little three-cylinder SmartCar conversion from FlyEco, but also some MIAs. Notably absent was Red/Raikhlin's 12-cylinder behemoth, which made the rounds last year, and Continental's TD300, which was quietly certified last December with absolutely no announcement whatsoever.
Cessna was expected to fly in its new SMA SR305-powered JT-A 182, but it didn't show because of weather, we were told. However, Diamond did have on display a detailed mockup of its new larger twin, the DA52 VII, powered by new variants of the Austro AE300 at 180 HP each. I got a flight demo in that aircraft after the show and found it quite impressive. More on that at a later date.
For now, the diesel market is to the overall engine market as LSAs are to overall airframe market. The technology has a foothold, but it's not yet dominant, despite the ongoing and perhaps worsening lack of confidence in avgas supplies. This would seem to present the ideal climate for diesels to explode in popularity, but perhaps with the exception of Diamond, the march to a Jet-A world seems to be a wandering meander. There's definite interest and progress, mind you, but it's slow. Consider that the U.S.-based DeltaHawk admits that it probably has the longest running engine cert project in aviation history.
The real surprise to me is Continental, which has vigorously committed to diesel, developing technology acquired from SMA for its own family of diesels. In this podcast last week, Continental's Rhett Ross said the company is certain Jet-A technology will open markets throughout the world, yet it's currently almost downplaying its own diesel. They didn't have it at Sun 'n Fun either and made no announcement of the certification. No one is saying why, but I surmise it might be a legal skirmish with SMA. We're told to expect big announcements at Oshkosh or later in the year. They've got an OEM and my blue sky guess is that it would be Cirrus, with a diesel-powered SR20. The SR22 would be a better candidate, but it will need more horsepower than the four-cylinder TD300 can deliver.
Ross's counterpart at Lycoming, Michael Kraft, said "interesting question" when asked if Lycoming had its own diesel in the works. Last summer, Lycoming announced that it would provide service and overhaul support for the SMA diesel, but there aren't yet enough of those in the field to make a dent in the market. Kraft has always said he thought the uptake of diesel would be slow, and it now looks like that's exactly what's happening. Still, I wouldn't be surprised to see some kind of announcement from Lycoming that either expands on the SMA agreement with regard to OEM work or conversions and/or a homegrown diesel from Lycoming. Sooner or later, the market is bound to turn in diesel's favor if we're not seeing it—in slow motion—already. And you can't sell what you haven't developed.
If the diesel market seems slow now, it wasn't always. It's fair to say Diamond pioneered the OEM diesel market with the Thielert-powered DA42. At the time of its introduction, I thought that (a) there was no market for a new twin and (b) even less of one with diesel engines. Wrong and wrong. Despite what seemed like a high asking price of $460,000, the DA42 proved hot, selling up to three a week during the 2005 to 2008 period. Counting singles and twins, Diamond has some 900 diesel-powered airplanes flying. In the current market, that's a big number.
What tanked it? Diamond CEO Christian Dries says Thielert's bankruptcy and subsequent jacking of prices to turbine levels made any more major OEM inroads unlikely. Recall that Thielert got into trouble before the recession and after the financial meltdown, its market prospects were unlikely to improve and didn't. Thielert has been operating in insolvency for five years and won't comment on any prospects for exiting that state. It thus seems unlikely that it will develop new products or even significantly improve what it has until that happens. Thielert engines are still hobbled by requirements for recurrent clutch and gearbox inspections. It's difficult to imagine that this model will remain competitive with Austro's and SMA's more powerful models that don't require the inspections. Long term, I don't think customers will put up with that if there's a choice.
Anyone who thinks gasoline technology is done better let Rotax know. The company's 912 iS is finding strong market traction, with some 300 in the field. At Aero, Rotax showed some test data that indicated the engine's fuel economy is considerably better than first claimed.
Life cycle costs of diesels are still a moving target. Given the low volume and high manufacturing costs, they're expensive to build and any recurrent replacement parts, such as pumps or gearboxes, only adds to that. The last analysis I did on the Austro AE300 against a Lycoming IO-360 yielded a $53.53 per hour cost for the Austro—inclusive of fuel—versus $66.50 for the Lycoming, not including any mid-run cylinder overhauls or typical mag work.
That's good, but not necessarily slam dunk if the diesel is more expensive to buy. Where it turns the corner is if diesels get to the high TBOs they are known for—say 2400 or even 3000 hours. If that happens, diesel economics are undeniably attractive. Of course, if you're in a part of the world where Jet-A is the only fuel available, the comparison is moot.
And that's what the diesel camp is counting on.