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." />

There’s often a general skepticism about the effectiveness of STCs, but I have personal knowledge that Power Flow’s products work as advertised. Three years ago, I had my Mooney fitted with a Power Flow exhaust, and the aircraft experienced a dramatic difference in performance. I picked up 50 to 75 fpm in climb, saw CHTs and oil temps drop by as much as 15 degrees, and witnessed an impressive five-knot speed increase at 11,000 feet.

In the case of the Diamond Star, Power Flow’s general manager, Darren Tillman, told me his company tweaked the exhaust to reduce back pressure, and the final system wound up delivering about an extra 23 additional horsepower. Incidentally, that doesn’t mean the certified, 180 hp Star now delivers 203 hp. The airplane is still certified for a maximum 180 hp. The tuned exhaust merely recovers the horsepower normally lost to power-grabbing accessories such as starter, alternator/generator, etc.

The extra ponies provide an additional five knots cruise at 6,500 feet, and as much as seven knots at 10,000 feet. Power Flow will supply the more efficient exhaust to Diamond Aircraft for all future DA40 XLs, and the company will also market the system as an STC’d conversion for stock DA40s equipped with the composite MT-Prop. (Pilots flying behind the Hartzell-driven Star must stick with the stock exhaust for now; Hartzell is working on an STC for the Power Flow exhaust, but it will likely also require a new Hartzell prop.) Price for the aftermarket DA40 Power Flow exhaust (with ceramic pipe) is $5,190, plus labor.

The new Star also has an improved MT composite, scimitar, three-blade prop to help convert the additional Power Flow horsepower to thrust. The new prop is pounds lighter than the old one, and you can feel that during power-up. The new prop comes up to speed notably quicker.

There are another half-dozen less-perceptible improvements to the Star that make the XL a fully equipped, ready-to-fly, IFR aircraft. Diamond analyzed how pilots typically order the Star, and configured the airplane with most of what was formerly optional as standard, offering the DA40 XL at an all-up tab of $339,695. (One of Diamond’s newest offerings, the DA40 XLS, comes at a $334,950 price tag. Learn more in the Sidebar.)

To offset the weight of the improvements, Diamond has recertified the DA40 to a gross weight of 2,646 pounds, 111 more than the previous Star. As a result, useful load increases by about 70 pounds. Maximum landing weight remains at the old 2,535 pounds, so if you depart at gross, you’ll need to burn off about 19 gallons of fuel before you can return for landing.

Inside the cabin, Diamond added electrically adjustable rudder pedals on both sides as standard, AmSafe inflatable seat-belt restraints and an electric CO2 detector. The company also incorporated a Power Flow heater to deliver air 25 degrees hotter than before. Outside the airplane, Diamond fitted high-intensity discharge (HID) taxi and landing lights.

Standard avionics on the XL include the Garmin G1000 and GFC 700 autopilot. They include traffic, XM weather and GPS-based terrain warnings.

Diamond emphasizes that many of the features above could become available as retrofittable options. As mentioned earlier, the Power Flow Systems exhaust is already available on the STC aftermarket.




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