Raytheon hobbles Av Partners by withholding wing data

 - May 15, 2008, 11:29 AM

Raytheon Aircraft’s failure to provide wing-structure data will delay by several months Aviation Partners’ blended winglet program for the Hawker 800, a program for which the Seattle-based modification designer had hoped to receive certification this summer.

Aviation Partners CEO Joe Clark told AIN, “We had hoped to be able to ink a deal with Raytheon to have them provide us data, but we haven’t been able to do that.” Clark said he had no idea why the data is not forthcoming, whether it’s deliberate reluctance or just not a high priority. “When I talk with the people at Raytheon, they seem excited about what we’re doing, but we can’t seem to get anything done with them.”

It’s a lot longer job when you don’t have OEM data, Clark said. “You can get the same data analyzing the wing structure [yourself] but it’s a lot more difficult because you have to do load studies and more. At least you have a starting point with the OEM data.” A spokesman for Raytheon Aircraft told AIN, “We want to work with Aviation Partners but first we must ensure a financial  [benefit] for both companies, and obtain a mutually agreeable proprietary data agreement. Then we can move forward.”

Nonetheless, Aviation Partners said it is going ahead with the program on its own, and certification is now expected in the first quarter of  next year. “We are very encouraged by both the marketplace [some 500 eligible airplanes] and the CFD [computational fluid dynamics] work we’ve done,” Clark said. “The CFD work matches flight-test data,  and we have verified a 7.3-percent drag reduction.” In addition to drag reduction, which translates into reduced cruise fuel consumption,  Clark said operators should experience a significant improvement in second-segment
climb performance.

The drag reduction and other aerodynamic benefits of the winglets will provide up to about 30 min more endurance (for about 180 nm more range), claimed Clark. “Initial cruise altitudes will be about 1,500 feet higher at the same weights. [The winglets] will make the Hawker 800 close to 6.5-hour airplane with reserves,” Clark added. “Blended winglets enhance longitudinal and directional stability, thereby providing better handling in turbulence.”

Aviation Partners believes it can keep the installed price between $300,000 and $350,000, despite the developmental time penalty from lack of OEM data. Installation downtime should not exceed 14 working days.

One of the biggest challenges in adapting the composite winglets to the Hawker 800 was the necessity to remove the aileron horn balance. Clark explained, “We rebalanced the aileron with tungsten in the leading edge of the aileron, which also lightens control feel.” The modification also includes removing the Hawker 800 stall fences and installing vortilons, as is done on the Gulfstream II winglet modification, enhancing low-speed handling, Clark said.

Aviation Partners flew its leased test Hawker 800 about 60 hr last year (more hours than the BBJ flew  in its winglet flight-test program). Modified airplanes will be designated the Hawker 800SP (for special performance).