DEE HOWARD has completed preliminary actuation system testing and begun initial forward-thrust performance testing of its next-generation thrust reverser. The system includes a patented variable-geometry nozzle (VGN), which, according to Dee Howard, provides improved thrust performance during take-off and initial climb.

The initial ground tests are being carried out in conjunction with AlliedSignal Engines using a TFE731 turbofan.

Most engine exhaust-nozzles have a fixed exit area designed as a compromise between providing maximum thrust at take-off and maximum fuel economy during cruise. "This results in less-than-optimum performance at all conditions," says Dee Howard. "However, the VGN system provides optimum exhaust areas at both take-off and cruise conditions."

As with other thrust-reverser designs, the target doors form the final engine exhaust-nozzle in forward-thrust mode. With the VGN system, the relative position of the doors can be varied, allowing the final exhaust exit to be to be switched between a smaller area for cruise, and a larger area for take-off and approach conditions, producing higher forward-thrust levels than a fixed-area nozzle. Initial tests have indicated that the nozzle will produce about 5% more thrust at take-off than a fixed-area device, says Dee Howard.

The San Antonio, Texas-based company says that it is in discussions with airframe and engine manufacturers about "...the possibility of incorporating a VGN thrust-reverser system on several applications".

International Aero Engines and Calcor Aero Systems announced earlier this year that they are jointly developing a variable-area exhaust nozzle for the former's V2500 turbofan (Flight International, 14-20 June).

Source: Flight International