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Tuesday, January 1, 2008

Rotor & Wing: Rotorcraft Report: Bell Tweaks Tail of 429 Light Twin

PRODUCTS | AIRFRAMES

Bell Helicopter was scheduled to freeze the design of its new light twin Model 429 last month and move into the final phase of certification testing in anticipation of first deliveries by year’s end.

The manufacturer in November completed separate sets of high-altitude and high-temperature testing in Alamosa, Colo. and Lake Havasu, Ariz. respectively, with two 429 prototypes, said Bill Stromberg, Bell’s executive director of the 429 program. The altitude testing in Alamosa confirmed a hover-out-of-ground effect capability of 11,000 ft on a standard ISA day, higher than Bell’s target of 9,300 ft.

To address some handling-qualities issues identified in testing, he said, Bell has added a strake to the 429’s tailboom design. The strake starts at the tail-rotor gearbox and extends forward about 3 ft. Bell also has modified the 429 vertical fin, sculpting it to unblock airflow from the tail rotor and increase tail-rotor authority. "We basically took area out of middle and put a 9-in extension on top and a 6-in extension on bottom," he said.

Bell also added ducting on the starter/generator to keep it within target temperature limits.

Bell has confirmed a Vh, or max speed in level flight with maximum continuous power, of 142 kt for the 429. The design has been flown to 170 kt, meeting regulatory requirements for testing 10 percent above the Vne, or never-exceed speed, of 155 kt.

Bell was to hold its last formal 429 customer advisory council meeting on Dec. 11-12 for final inputs on the design, and an internal "gate" review Dec. 17 before moving forward with the program.

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