Friday, June 1, 2007
Diamond Twin Star: 21st Century Multi
Diamond Aircraft, the world’s third-largest manufacturer of GA, fixed-wing aircraft, is betting that the diesel-powered Twin Star will be the multi trainer of the future
Take FADEC, for instance. Full Authority Digital Engine Control regulates every parameter of engine operation except manifold pressure, expressed as percent of horsepower on the Twin Star. From startup to shutdown, FADEC samples air temperature, atmospheric pressure, humidity and throttle position to manage electronic fuel injection, rpm, mixture and timing, and deliver optimum performance and fuel efficiency for any conditions through a single lever for each engine.
Whether you’re flying a max gross takeoff out of Leadville, Colo. (elevation 9,927 feet MSL), or merely cruising at 6,500 feet over Cape Cod, the Engine Control Unit reads the engine environment, optimizes power and fuel burn, turns the electric fuel pump on and off as necessary, regulates ignition timing and minimizes the possibility of out-of-limit cylinder and exhaust gas temperatures. In short, FADEC diagnoses and automates all engine functions.
This simplifies the pilot’s job and allows him or her to concentrate on navigation, communication and simply enjoying the trip. The standard avionics suite for the Twin Star is the Garmin G1000–integrated, two-screen, flat-panel display. Once you learn the operating principles, the G1000 automates communication and navigation functions nearly as much as FADEC does engine operation.
The bottom line is simplicity that initially threatened one of the Twin Star’s primary missions. The FAA originally questioned whether FADEC’s automation and the lack of prop and mixture controls compromised the airplane’s ability to train pilots for the multi-engine rating. The question was whether the airplane was truly a “complex” design, since the props weren’t traditionally controllable. Eventually, the FAA concluded that the props were controllable, even if controlling them required only moving the throttle. In the event of a failure, the pilot still needed to identify the sick engine and shut it down, feathering the prop, even if that process was as simple as flipping a single switch.
Indeed, single-engine operation is about as uncomplicated as it can be without incorporating an auto-feather system. During the air-to-air formation session that produced Jessica Ambats’ photos, I shut down the left engine and chased the Cessna Skylane photo ship around the clouds above Catalina Island with the left prop caged. The shutdown and restart process consisted of merely turning off the appropriate ECU, then switching it back on when it was time to restart. Uncommanded yaw was mild, and the Twin Star remained docile while in single-engine formation.
Whatever the mission, Diamond configured the DA42 to offer super-simple operation, a large, comfortable cabin and something no other manufacturer has—a back door. Both the single-engine Star and Twin Star feature a fold-up door at aft left, allowing independent access to the rear two seats. Pilot and copilot board through an overhead hatch that hinges at the front and rotates up and forward. The cabin measures 46 inches across, nearly as wide as a cabin-class Piper Navajo.
Standard fuel is 50 gallons, but practically everyone opts for the long-range, 76-gallon tanks. Climb is excellent; the turbos’ critical altitude is 8,000 feet, so as long as your body can take it, there’s no reason not to fly at 10,000 to 12,500 feet on practically every flight. Incidentally, single-engine service ceiling is 10,000 feet.
When level at 12,500 feet with 80% power dialed in, you can expect about a 160-knot cruise speed on 12.5 gph. Extrapolate that over five hours, and you could reasonably expect to transit 800 nm at one sitting. If you have the inclination and the time, you can pull back to 50%, endure for more like 9.5 hours and range out nearly 1,200 nautical miles.
At this writing, Twin Stars are fully assembled and certified in Austria, then disassembled and shipped to Diamond’s London, Ontario, Canada, facility where they’re reassembled and ferried to the various North American dealers. Within a year, the Canadian plant will begin producing its own Twin Stars.
Current base price of the Twin Star is $527,313, including FADEC and the G1000. TKS known icing and a number of other options can elevate that figure well above $550,000. Air-conditioning, the ultimate luxury, is expected to be available sometime in 2008.
Initial sales of the Twin Star have been encouraging. Lufthansa has ordered 40 for its European training facility and Embry-Riddle Aeronautical University in Daytona, Fla., has contracted for 10 more, and current deliveries and orders total more than 700.
Since designers began mounting a second engine on airplanes in search of redundancy, the industry has struggled with the problem of asymmetric thrust and twin-engine safety. The Diamond Twin Star doesn’t totally solve the problem, but its unusual combination of automatic systems and easy handling may make it one of the simplest—and safest—twins in the sky.
SPECS: 2007 Diamond DA42 Twin Star
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Labels: Piston Twins