AirVenture: The Diesel Dance
To say that aviation development and market uptake moves glacially is an insult to glaciers everywhere, or at least the piles of dirty snow that pass for glaciers in a world where average summer temperatures make Venus look temperate. I can develop a fairly long list, but let’s consider diesel engines for the moment.
These make perennial appearances at AirVenture and like the pixel-addled zombies that we are, we dutifully troop off to the press conferences, write down what the people say and then stumble off to the hangars to recover in one of those Magic Fingers chairs while the guy in next booth flogs copper-bottom pots. Yeah, I did it last year and never even got the massage.
This year, the Wisconsin-based startup, EPS, had a press conference and so did DeltaHawk. Remember them? EPS showed; DeltaHawk didn’t, although they were on the field. You can hear about EPS’s latest progress in this podcast.
Cutting to the chase, the EPS engine is a high-output diesel capable of up to 450 HP, so it targets high-performance singles and twins, utility aircraft and the UAV market. The company claims to have provisional orders for more than 1000 engines, without saying who the customers are. It’s an innovative 180-degree V-8 configuration with one crankpin sharing two rods, so the engine is shorter. But at 657 pounds installed, it’s still heavier than a gasoline engine on a power-to-weight basis. If the company’s numbers are accurate, it has stunning fuel specifics: 0.32 BSFC compared to 0.35 for the diesels already out there and 0.42 for typical gasoline engines.
Without occupying the minds of the people who buy these engines—and that’s OEMs, not aircraft owners—it’s hard to know how much such sunny numbers sway them, if at all. Consider Cessna’s on-again-off-again but mostly off-again flirt with diesel. It pulled the plug on a Skyhawk diesel in 2007 just as Thielert was about to sink. Then it announced the 182 JT-A in 2012 with the SMA SR305-230 diesel, only to flatline that project in 2015. This spring, Cessna killed the diesel Skyhawk using Continental’s CD-155.
Piper is hanging in with its CD-155-powered Archer DX, but it doesn’t appear to be a strong seller. We know Cirrus has flown various diesels in the SR22; we don’t know if they’re remotely interested in offering a diesel model. My guess would be … maybe, but probably no. Mooney has its diesel M10 trainer project in limbo, if not abandoned entirely.
Along with a few conversions, Diamond still owns what there is of the diesel market, which by my estimation, is about 7 to 9 percent of total new GA piston aircraft. Like the EPS engine, the Austro four-cylinders Diamond developed have impressive fuel specifics and are, bar none, the smoothest running powerplants in piston GA. But they’re heavy and more expensive than gasoline engines. But this may not matter to a buyer who can afford a $1.4 million DA62.
And this gets me to the wrong-assumption stage of the discussion. With the exception of Diamond, airframers are not exactly risk takers. Volumes and margins on GA airplanes are thin at best and a clean sheet innovative airplane that tanks—always a good chance that it will—takes the P&L with it. Ask Diamond about that after the DA42 teething pains with the original Thielert engines.
Sure, OEMs want performance and economy to juice the ad copy, but they just as desperately want to avoid a turd of an engine that may suffer from infant mortality and a vaporous supply chain and support structure. You can practically get parts for a Lycoming at NAPA, but a new-age diesel? Not so much.
And that’s where I think innovative powerplant developers run off the rails. It’s not enough to have great performance, impressive fuel specifics and single-lever control; OEMs also want companies that appear to have legs and staying power in the commercial sense. That, more than anything, makes breaking in with a new engine daunting as best, improbable at worst.
Fears about the extinction of leaded avgas were once driving this, especially in the U.S., but even as the FAA has all but surrendered on an unleaded replacement, I don't sense much concern. Owners aren't asking us what we think is going to happen. Not that I have a clue in hell anyway. But diesels—especially new, unestablished ones—will have a steep uphill slog to gain market share. Technical excellence or lack thereof may have nothing to do with it; market inertia may drive it. And evidently, except for a small niche, pilots love gasoline.