A Diesel In Your Future?


Aero Diesels Gaining Momentum…

Although many skeptics predicted the government approvalswould be years in the making, German manufacturer Thielert Aircraft EnginesGmbH announced last Friday that it has certified its 135-horsepower TAE 125diesel for the Cessna 172N and P models. The conversion will sell under thebrand name Centurion 1.7, which designates the engine’s 1.7-liter displacement.The German joint aviation authority (Luftfahrt-Bundesamt) OK’d the paperworklast week, paving the way for certifications in the U.S. under bilateralarrangements with the FAA. Thielert’s marketing partner in the U.S., SuperiorAir Parts, told AVweb Friday thatfollow-on approvals will expand the range of older Skyhawks suitable for dieselconversion and STCs for Piper’s PA-28 Cherokee series will arrive soon after.As for new aircraft, Cessna recently told AVwebthat it has no plans to fit new Skyhawks with diesel engines for now, but thecompany may change that tune if Thielert gains a foothold in the world aerodiesel 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-belchingimage of ground-bound diesels by calling their powerplants "jet-fuelengines." The engines do enjoy the impressive fuel specifics of dieselengines and like modern road diesels, smoke belching is a thing of the past,thanks to improved induction and electronic fuel-control systems. With claimedfuel burns in the 4 to 5 gph range, the Centurion 1.7 would have fuel specificsof about BSFC (brake specific fuel consumption) .33, compared to.42 to .45 fortypical equivalent Lycomings. It’s also turbocharged … so don’t be surprisedto see a diesel-powered Skyhawk pushing 140 knots in the high teens. Given thelower cost of Jet-A and the lower fuel burn, Thielert claims a diesel-poweredSkyhawk’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 VPfor engine development, Terry Wood, told AVwebthat the Skyhawk flyaway conversion price will be about $40,000; more thantwice what a conventional Lycoming overhaul costs. And unlike the Lyc, theCenturion 1.7 has a TBR — that’s time between replacement — not aconventional TBO. Replacement cost will be $19,900 at a proposed initial TBR of2,400 hours. Wood says Superior’s primary market may be flight schools that, hesays, will benefit from the lower operating costs. Thus far, Thielert appears tohave a leg up on the competition with Diamond’stwin 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 besold in Europe first; North American marketing plans may follow sometime in thefuture. SMA has a certified diesel and althoughCirrus and Maule have expressed enough interest to begin testing orcertifications, no SMA aftermarket conversions are available yet. Both Lycomingand Continental appear to have tabled diesel projects.