WORK ON THE replacement heavy-fuel engine (HFE) for the TRW/IAI Hunter short-range unmanned air-vehicle (UAV) has been suspended because of weight problems associated with the powerplant selected late in 1994.
In October, the Pentagon awarded TRW $38 million to qualify a diesel-fuel-burning engine for the Hunter joint tactical UAV, now powered by an Italian-made Motto-Guzzi gasoline engine.
TRW, in turn, selected the team of Lockheed Martin Armament Systems and Rotary Power International to adapt an RPI-developed twin-rotor 40 Series turbo-charged powerplant for the short-range drone. The team, led by the Lockheed Martin unit, received a $13 million contract in November to qualify the twin-rotary-engine installation. Production contracts for 1,000 engines would be worth over $50 million.
US Army Col Paul Tanguay, joint tactical UAV programme manager, reveals, however, that the HFE's weight is "significantly higher than the promised weight of 107kg." He says that the stop-work order issued by TRW in June has been extended to 5 August so that the Pentagon can evaluate alternative powerplants while the engine team attempts to fix the weight problem.
Jack Manning, the engine team manager, says that the solicitation did not specify a maximum weight. After the engine passed a critical endurance test, achieved a power growth and came within fuel-consumption limits, it was determined in January at the preliminary design review that the powerplant needed larger heat exchangers, which caused its weight to grow to 120kg.
"We feel the 120kg engine design is realistic, achievable and within allowable risk...We think we have a good solution...We've met all requirements, and we are within 10% of our proposed weight," says Manning.
Williams International hopes to step in with the 30kW (40shp) WTS117 turboshaft. TRW began talking with the US engine-maker about an alternative engine in April. Other firms which may seek the work are AAI, offering a modified rotary powerplant developed by UEL (ex-Alvis UAV Engines), and Sundstrand, with a turbine engine.
Source: Flight International
