Plane & Pilot
Tuesday, October 23, 2007

Diamond DA40 XL: Polishing The Diamond Star

The new Diamond DA40 XL incorporates new aerodynamics, an improved, composite prop and an advanced exhaust system to increase the knot count

Diamond DA40 XLAsk anyone who’s tried to wring more speed from an existing aircraft design, and you’ll learn that the task is very difficult. Hot-rodders have long been adding speed on cars and motorcycles by installing progressively more powerful engines, and that works great for machines that roll on wheels. Unfortunately, it’s not nearly as effective on airplanes." />

The big question is, what are the results of all this innovation? The Diamond dealer in my neck of the woods is USAero ( in Long Beach, Calif. Robert Stewart, USAero’s Diamond expert (he also dabbles in emeralds and turquoise), agreed to fly with me to demonstrate the new airplane’s talents.

Since the first Diamond Star hit the market in 2000, the little four-seater has been almost universally regarded as one of the most innovative singles in its class. With a composite design that has little hanging out to grab the wind, even the original Star offered excellent performance on minimal horsepower.

Standing on the XL’s wing provides perhaps the optimum view of the airplane’s slick aerodynamics. There’s nary a rivet or section line in sight, the overhead hatch fits so tight, you have to practically open a window to get it closed, and, oh yes, there’s even a back door on the left, something rarely (if ever) seen on a four-seat airplane. (The old Beech Sierra offered an aft right rear door, but at the time, Beech was laboring under the delusion that the airplane was a six-seater.)

Settle into the airplane’s plush leather interior and you can’t help but be impressed with the nearly automotive comfort. Diamond didn’t design the interior around the BMW 5-series or Audi A8, but the cabin still winds up being eminently comfortable, measuring 47 inches across in front, 45 inches in back.

That’s not to suggest you can top the tanks and fill the four seats with 680 pounds of people. Even with the gross weight increase, the test airplane sported a payload of only 850 pounds. Subtract 50 gallons of petrol, and you’re down to more like 562 pounds for people and their stuff.

I know it’s a song you’ve heard before, but that’s not really such an evil limitation, because most pilots buy at least two seats more than they need. Besides, if you really need to fly with a 680-pound string quartet (minus their instruments), you could leave 20 gallons in the truck and still have enough fuel for a 250 nm trip plus reserve.

Level at 6,500 to 7,500 feet with a full load, and you’ll see something between 148 and 150 knots, again not too shabby with only 180 hp under the bonnet. I actually saw 151 knots true on the day of my flight, though we were operating perhaps 200 pounds below gross.

Labels: Piston SinglesSpecs

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