Plane & Pilot
Tuesday, March 27, 2012

Diamond's Twin For 2012

The Diamond DA42 comes with your choice of Lycoming GASOLINE or Austro diesel engines

The first Diamond DA42 was introduced in 2005, and was the first certified, all-composite multi aircraft, constructed almost entirely of carbon fiber.
The question back in 2004 was, "Does the world really need another piston twin?" The type had fallen from some 20 models in the early 1980s to only three by 2004. Piper offered the Seminole at the bottom of the market, and the turbocharged Seneca V in the midrange, and Hawker Beech topped the class with the million-dollar 58 Baron. Sales weren't exactly outstanding, but there was enough interest to justify continuation of the models.

Diamond Aircraft of Austria reasoned there was room for one more multi. The first Diamond Twin Star was introduced in 2005, and it represented a paradigm shift in the whole philosophy of piston twins. The DA42 was the world's first certified, all-composite multi, constructed almost exclusively of carbon fiber. It also incorporated Garmin's innovative G1000 glass-panel avionics suite, another game-changing improvement.

Perhaps most significantly, however, the new Diamond employed engines that were cutting edge in technology, yet with roots in the 19th century. The diesel dates back to 1893 when Rudolph Diesel's compression-ignition engine was first patented. If your knowledge of diesels extends little farther than the old smoky Mercedes 190D sedan in the driveway across the street, don't feel alone. Diesel engines forego spark plugs altogether in favor of extreme compression ratios, on the order of 15-24 to one, that use the heat of compression to ignite the fuel/air mixture without benefit of a spark plug. (In contrast, avgas-powered piston engines rarely exceed 10-to-one compression.) It took nearly 100 years before someone figured a way to make diesel engines viable in an airplane.

Diamond's twin features FADEC diesels that are, strangely enough, a century ahead of Rudolph's first design. The initial Diamond Twin Star could burn jet fuel, a major advantage in those parts of the world where avgas is scarce or nonexistent. The DA42 offered a pair of German Thielert Centurion powerplants, a variation on Mercedes' automotive turbo-diesels. The Thielerts were rated for 135 hp each, burned a miserly 6.5 gallons/engine/hour and, at least theoretically, sported a 2,400-hour TBO.

None of the airplanes had the chance to reach that TBO. Thielert went bankrupt in April 2008, leaving Diamond with nearly 500 orphan twins and almost 400 diesel singles, with limited technical support and no warranty. As a result, Diamond had no choice but to halt production of the Twin Star until they could develop their own diesels to replace the Thielerts. Perhaps ironically, the company had captured something like 80% of the light-twin market when production was suspended.

In the interim, Diamond rushed development of the DA42-L360, essentially the same airplane fitted with conventional Lycoming IO-360 powerplants. These are fuel-injected engines, similar to the carbureted O360s mounted on the Piper Seminole, and rated for the same 180 hp. With 90 hp more enthusiasm at sea level, the resulting airplane was an impressive performer, but the trade-off was that fuel capacity remained the original 76 gallons. Burn jumped to 9.5 gallons/engine/hour, and endurance at 75% was reduced to three hours plus reserve. Fortunately, that wasn't a terrible disadvantage in training mode where flights rarely exceed 1½ hours.

Labels: Piston Twins


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