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
Ask 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." />
Remember, however, that specific fuel consumption is immutable. The more horses you employ, the faster your airplane will go, but you’ll also burn more fuel. Diamond claims the Power Flow system makes that about 10 gph at 75%. That suggests an SFC of 0.444 pounds/hp/hr. With 50 gallons aboard, you should be able to range out an easy four hours plus reserve—about as long as most pilots are willing to sit in one place anyway.
“Realistically, the Power Flow exhaust is probably the major contributor to the improved performance,” says Stewart. “All by itself, it accounted for at least five knots of the higher cruise.”
Diamond’s max-cruise spec is 150 knots, and we were right on the numbers. That’s excellent performance for a 180 hp single with wheels in the wind. Granted that speed, you’ll run away from an Archer or Skyhawk, though you’ll still be at least five knots slower than a Cirrus SR20. Pull back to 55%, and you can see 130 knots on eight gph.
Personally, I’ve always felt the Star was the most aerodynamically innovative airplane in the class. That class, incidentally, consists of the Star, Cirrus SR20, Piper Archer and Skyhawk SP. (Arguably, you might include the Skylane, though it employs 50 more horsepower to cruise at roughly the same speed.) The Archer and Skyhawk have been around for at least four decades, whereas the Star and SR20 premiered less than 10 years ago.
Using Jane’s All-The-World’s Aircraft 2006/2007 or Diamond Aircraft’s Website, you can see how the numbers compare for the four contenders. It’s just about impossible to keep these comparisons from matching apples to grapefruit, but these are the best numbers we could assemble.
The new Diamond Star represents a definite improvement over the previous version, not just a rehash of the original airplane with new paint and a fancier interior. Now that Diamond has introduced the DA50 Super Star to compete head-to-head with the Cirrus SR22, Columbia and Mooney Ovation, the DA40 XL raises the bar in the midpriced, four-seat, fixed-gear class.
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