Height-Velocity Testing of a Growth Rotor for the Bell 407 Aircraft

Bell Helicopter performed height-velocity testing at Alamosa, Colorado during the summer of 2005 and the spring of 2006. Three different main rotors were tested, including the baseline 407 rotor, a 407 rotor with increased inertia, and a 407 growth rotor with increased chord, diameter, and inertia. Complete H-V curves were developed for each configuration, including points from low hover, takeoff, and fly-in. Pilot qualitative data and quantitative data from the highly instrumented aircraft were obtained. The purpose of this flight test program was to investigate key rotor parameters that would be required to increase the H-V gross weight capability of the Bell 407 by approximately 600 lb at 7,000 ft density altitude (272 Kg at 2,134 m). The key parameters include rotor rpm, rotor inertia, rotor diameter, and rotor chord. This paper discusses the procedures for each component of H-V testing and the associated civil certification requirements. Time history data are presented for a sample of test points, allowing a detailed look at the throttle chop, flare (if any), collective pull, and landing. Delay time, holdoff time, flare attitude, maximum load factor and thrust coefficient, and rpm at touchdown are examined. Results indicate that the new 407 growth rotor will increase the H-V maximum gross weight capability by 570 lb at 7,000 ft density altitude (258.5 kg at 2,134 m) while also reducing the airspeed at the knee of the H-V curve by 20 knots (37 km/h) and reducing the altitude of the high hover point by 210 ft (64 m).