A Diesel In Your Future?
Aero Diesels Gaining Momentum...
Although many skeptics predicted the government approvals would be years in the making, German manufacturer Thielert Aircraft Engines GmbH announced last Friday that it has certified its 135-horsepower TAE 125 diesel for the Cessna 172N and P models. The conversion will sell under the brand name Centurion 1.7, which designates the engine's 1.7-liter displacement. The German joint aviation authority (Luftfahrt-Bundesamt) OK'd the paperwork last week, paving the way for certifications in the U.S. under bilateral arrangements with the FAA. Thielert's marketing partner in the U.S., Superior Air Parts, told AVweb Friday that follow-on approvals will expand the range of older Skyhawks suitable for diesel conversion and STCs for Piper's PA-28 Cherokee series will arrive soon after. As for new aircraft, Cessna recently told AVweb that it has no plans to fit new Skyhawks with diesel engines for now, but the company may change that tune if Thielert gains a foothold in the world aero diesel market.
...And The Numbers Add UP (Sort Of)...
Speaking of marketing, Thielert and its chief competitor, France's SMA, prefer to distance themselves from the stinking, smoke-belching image of ground-bound diesels by calling their powerplants "jet-fuel engines." The engines do enjoy the impressive fuel specifics of diesel engines and like modern road diesels, smoke belching is a thing of the past, thanks to improved induction and electronic fuel-control systems. With claimed fuel burns in the 4 to 5 gph range, the Centurion 1.7 would have fuel specifics of about BSFC (brake specific fuel consumption) .33, compared to.42 to .45 for typical equivalent Lycomings. It's also turbocharged ... so don't be surprised to see a diesel-powered Skyhawk pushing 140 knots in the high teens. Given the lower cost of Jet-A and the lower fuel burn, Thielert claims a diesel-powered Skyhawk's direct fuel operating costs will be reduced by 70 percent.
...But There's No Free Lunch
Still, the cost of admission won't be cheap. Superior's VP for engine development, Terry Wood, told AVweb that the Skyhawk flyaway conversion price will be about $40,000; more than twice what a conventional Lycoming overhaul costs. And unlike the Lyc, the Centurion 1.7 has a TBR -- that's time between replacement -- not a conventional TBO. Replacement cost will be $19,900 at a proposed initial TBR of 2,400 hours. Wood says Superior's primary market may be flight schools that, he says, will benefit from the lower operating costs. Thus far, Thielert appears to have a leg up on the competition with Diamond's twin turning Thielert diesels, with a Thielert-powered Diamond Star DA40 (single), the new DA40-TDI, launched from the factory at Wiener Neustadt, Austria, late last year, with plans to offer the aircraft in Europe. It will be sold in Europe first; North American marketing plans may follow sometime in the future. SMA has a certified diesel and although Cirrus and Maule have expressed enough interest to begin testing or certifications, no SMA aftermarket conversions are available yet. Both Lycoming and Continental appear to have tabled diesel projects.