Diamond has frozen the aerodynamic configuration of the D-Jet single-engined personal jet, which now includes new upswept wing-tips the company claims have "a positive effect on stall speed and roll control".
The company previously tested the Williams FJ33-5A-powered single with straight wing-tips followed by conventional winglets before selecting the final iteration.
D-Jet number three came to AirVenture with new wing-tips
Peter Maurer, president and chief executive of Diamond’s Canadian operations, says the new modified wing-tips improve "the overall aesthetics" of the aircraft and customers "liked the optics" of winglets. However, the conventional winglets the company flight tested did not provide maximum benefits in the D-Jet’s speed range, he says.
The new winglets, which initially underwent wind-tunnel testing, increase wing area and wing dihedral, improving roll stability and decreasing stall speed, says Maurer.
Diamond is displaying prototype aircraft number three with the new wing-tips as part of a "jet day" on 26 July at the Experimental Aircraft Association’s AirVenture show in Oshkosh, Wisconsin.
Maurer says the two flight test aircraft have almost accumulated 700h of development flight test time, including 200h on aircraft three, and the company is "very pleased" with the results. He says recent flights have focused on verifying compliance with the Federal Aviation Administration (FAA) Part 23 requirements in preparation for formal certification tests later.
Conventional winglets did not provide maximum performance for the D-Jet
Included are handling, stability and control throughout the weight and balance envelope, tests of stall speeds and stall characteristics at various weight and balance points and with different system configurations, basic system testing, expansion of the speed envelope to a maximum operating speed of 346kt (640kph), or Mach 0.56, and "much detailed development work, such as fine tuning the control forces and determination of the stick pusher activation point".
In parallel, the company has successfully completed limit load pressure tests on a ground test aircraft and more than 30,000 maximum cabin pressure cycles on a full scale test article fuselage. Other ground testing includes validation of the engine bleed air and cabin pressurisation systems, structural testing, landing gear tests and composite material qualification testing.
"We are now focusing on the production of tooling for MSN004 [the first production conforming aircraft]," says Maurer. "Once 004 is flying, it will take approximately another year to achieve type certification with initial deliveries scheduled in Q3 2014."
Maurer says Diamond will revisit the price of the aircraft, listed at $1.89 million in 2008, but would like to keep it below $2 million in today’s dollars when it enters service.
Diamond had suspended work on the jet in March 2011 due to funding issues, but later gained new investors and restarted testing in September last year. The aircraft was originally scheduled to enter service in 2006.
"We look forward to the day that we start deliveries of the D-Jet and are most grateful for the patience and loyalty demonstrated by our customers, our business partners, and our employees," says Maurer.
Source: Flight International