Plane & Pilot
Tuesday, March 25, 2014

What’s Up With Diesel?

Diesel power was once touted as the savior from the threatened avgas shortage. Is that still true?

For its part, Cessna isn't letting on what they've planned for the Skylane JT-A, especially considering that the model isn't certified yet. An engine failure last August cast a pall on certification efforts, though the pilot walked away, and the aircraft was undamaged in the emergency landing.

Cessna CEO Scott Ernest manifested little interest in the diesel-powered Skylane at last year's NBAA Convention, though neither he nor anyone else at Cessna has uttered a truly discouraging word. Cessna has built something like 22,000 model 182s since the 1950s, and most pilots can't imagine a sky without Skylanes.

A few other manufacturers have shown serious interest in jet-burning diesels, though the type is more popular overseas where avgas is already becoming scarce, and a gallon can cost $10. So far, none of the American airframe manufacturers have committed to development.

Cirrus Aircraft enjoyed a good year in 2013 with 276 aircraft sold, and for that very reason, they may be more determined to stay the current course rather than make a left turn toward diesels. The company is spending a ton on development of the Vision Jet project, and that may make them an unlikely candidate for diesel power, at least in the short term. The Vision is still scheduled for first delivery in late 2015.

Piper also had improved sales in 2013, and the company looked at the available diesel power plants, as well, but hasn't gotten beyond the looky-loo stage. Certainly, a major concern for any prospective aircraft company is the certification costs involved to produce what might be only 50-100 airplanes a year. The FAA has made it practically cost prohibitive to even consider certifying an airplane with diesel power.
Diesel aircraft engines do have several advantages over avgas mills: fuel availability and efficiency.
Nevertheless, diesels are far from dead. Lycoming has a turbo-diesel engine that's a total mystery to general aviation, the DEL-120, a 205 hp engine that currently powers drones for the military. Lycoming gave us a firm, "No comment," when we called and asked for details about the DEL-120.

In addition, Continental Motors recently concluded negotiations to quietly acquire the revived Thielert diesels of Germany. Thielert now builds the Centurion diesels, variations on the start-up power source for the first Diamond twins mentioned above. Premier Aircraft of Fort Lauderdale is in the process of pursuing an STC to install Thielert diesels in reconditioned late-model Cessna 172s, producing what will be in essence a fully rebuilt Skyhawk.


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