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

After the final lights/camera/action check, the DA42-NG turns out to be an enthusiastic performer. With two up-front and full mains (50 gallons), the test machine scored an easy 1,300 fpm climb. That was at 90 knots Vy.

I tried a 120-knot cruise climb, and the VSI only dropped to about 1,000 fpm. It's apparent the airplane's low-drag signature provides an efficient trip uphill.

At 10,000 feet, the NG was still scoring over 1,000 fpm up at Vy. The L360 Lycoming model with normally aspirated engines would probably be down to 800 fpm or less at that height. Both models are approved for a max altitude of 18,000 feet, but it's guaranteed the force-fed NG will reach that height sooner and with far more reserve power. The NG also offers over double the single-engine service ceiling (14,000 feet) of the L360 (6,400 feet).

In training mode, the NG again has the edge because of the turbo. Vmc and stall are virtually the same on both airplanes, so there's little chance of getting into real trouble. The NG's turbos provide consistent power to 14,000 feet, the critical altitude. Vmc demonstrations will be consistent all the way up, whereas the standard Lycomings lose power with altitude, so a Vmc demo in the L360 above, say, 5,000 feet, should be fairly easy. The airplane's reduced power up high won't induce much of a roll, no matter how badly you abuse power management.

When it's time to cruise, the NG scores an impressive 180 knots-plus at 14,000 feet, provided you're willing to wear the mask. Operationally, 10,500 or 12,500 are more realistic altitudes, and our cruise checks suggested an easy 163 knots at 10,500 feet, 175 knots at 12,500 feet. Come back to 60% power, and you can see 150 knots on about 10 gph total. That means endurance with the 76-gallon tanks is an easy six hours, worth probably a 900 nm range. Diamond suggests a max range of 1,180 nm, presumably at higher altitude. FADEC manages mixture control automatically, adjusting the flow to any power setting. It's reassuring that the NG's turbo diesels allow a single-engine service ceiling of 14,000 feet.

The DA42's high wing loading imparts a ride that's serene even when the sky isn't. The airplane has almost a locomotive's sense of straight ahead, and the Garmin GFC 700 autopilot is nearly psychic on climbs and descents once you've psyched out which button to push.

Descents can be as you like them, since the engines are water cooled. You can practically treat the diesels like turbines, reducing power to 30-35% for letdowns without fear of shock cooling. Similarly, landings are the next thing to automatic. Ninety-five knots works well around the pattern, and 85 knots is plenty on short final. Dirty stall is only 61 knots, so if the runway is short, you can come back to 75 knots without violating the 1.2 Vso rule.

The DA42 NG continues in production,and Diamond plans to keep the London, Ontario, Canada line running. For the nonce, the company is emphasizing the engine-replacement program. When general aviation recovers from the financial doldrums of the 2008 recession, the Diamonds' unique combination of 21st/19th century technology should make them leaders of the pack. The NG is already out front.

Labels: Piston Twins


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