Diamond is selling a pair of brand new twins based on the company’s innovative DA42 design. The Austro diesel-powered DA42 NG is certified in Europe (EASA), with U.S. certification coming soon, and the Lycoming-powered DA42 L360 has just earned the FAA’s OK.
I had the chance to fly both airplanes recently at Diamond’s North American headquarters in London, Ontario, Canada, and the airplanes are both clear improvements in numerous ways over the original Thielert-powered twin that Diamond launched in the United States in 2005.
How Diamond arrived at the point that it’s selling not one but two distinctly different versions of its all-composite twin is a complicated tale. But it’s one that speaks volumes about the agility of the Austrian airplane maker when faced with challenges, the risks and rewards associated with riding the cutting edge in airplane design, and the difficulties potential buyers face when assessing those risks.
Twin Star: History of Innovation
In developing its Twin Star light multiuse twin, Diamond created that rarity of rarities: a true, clean-sheet airplane. While the long, high-aspect-ratio wing is similar in spirit to other Diamond designs and in keeping with its sailplane ancestry, there’s nothing derivative at all about the DA42. (The name Twin Star, by the way, is no longer used by Diamond.)
This is why, when it was developing the twin’s design a few years ago, the company seemed torn over the choice of powerplants. The conservative call was the 180 hp Lycoming IO-360 powerplant, a conventional avgas-burning four-banger that Diamond had been using for several years in its DA40 Diamond Star single. The innovative — and somewhat risky — call was to go with a new engine, an automotive turbodiesel powerplant repurposed for aviation use.
As we all know, Diamond went with the diesel, the Thielert Centurion 1.7 liter, a Mercedes conversion done up for aviation use by German company Thielert Aircraft Engines. While the Lycoming was well-known and trusted, the Thielert engine had some irresistible advantages. Despite the fact that it was only a 135 hp engine, compared with 180 hp for the Lycoming, the German diesel was, well, a diesel. And because it burned jet fuel, it could be fueled just about anywhere and, in many parts of the world, for far cheaper than airplanes requiring 100LL. And because it was an engine designed to be computer-controlled on the Mercedes sedans into which it was intended to go, computerized engine control, “fadec” in aviation parlance, was a natural, as well. So pilots would get a number of pluses: easy starting, no-brainer engine management and silky smooth power across the curve.
What sealed the deal, though, was fuel burn. In a day and age when fuel costs drive flight training decisions, the Thielert engines turned back the clock, giving fuel burns of less than 10 gph — combined — for typical training-scenario power settings. When I got my multi ticket in the DA42 at European American Aviation (EAA) in Naples, Florida, a couple of years ago, the flight school had just taken delivery of its second DA42 and was eagerly awaiting a third. The airplanes were flying nonstop, earning money for the school and requiring very little in return. And EAA’s experience wasn’t unique. For a time, Diamond couldn’t make the twins fast enough.
Unfortunately, we all know that that happy scenario quickly devolved into near chaos. The engines turned out to be too good to be true, and the ongoing engine maintenance costs, which few looked at carefully enough, turned nightmarish. In particular, the Thielert’s clutches were problematic. Not only did they require very regular overhaul — every 300 hours, in fact — but owners also had to send them back to Germany for the work, an expensive and time-consuming process.
The final straw came in early 2008 when Thielert, already under investigation from regulators for financial improprieties, declared insolvency, leaving the future of the Thielert engines, and that of the DA42, in jeopardy. The company parted ways with its founder and was taken over by a government insolvency administrator, who as part of the recovery plan declared warranties on existing engines null and void.
Shortly thereafter, facing an outcry from its DA42 owners, Diamond officially abandoned the Thielert engines, all the while putting pressure on the administrator to help DA42 owners keep their airplanes flying by lowering the prices of spare parts and overhauls.
Around that time, Diamond announced its intention to develop a Lycoming-powered DA42 model, on which it had already completed considerable work during the DA42’s initial development.
However, it was still crisis mode for DA42 owners. The high prices for Thielert’s engine parts, and their poor availability, left many DA42s grounded for lack of parts or parked for economic reasons.
Many DA42 operators called for Diamond to make them whole — either by honoring the engine manufacturer’s original warranty or by paying the cost of converting their Thielert airplanes to alternative power once those conversions were available.
While it was not obligated or able to do either of those things, Diamond has worked, despite the recession, to create new power options, as well as create what it says are attractive purchase options for many operators who want to trade in their Thielert-powered DA42s for newer models.
What Diamond was able to accomplish in the past 18 months — successfully launching and certifying two new versions of its twin during the worst economic downturn in 80 years — seems nothing short of miraculous.
There’s other good news. The insolvent Thielert company still won’t cover previous engines under warranty, but it has reduced the prices of parts for those engines and cut overhaul costs substantially.