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Allied near to completing F-22...

AlliedSignal is in "the final throes" of high-altitude testing of the auxiliary-power generating system (APGS) for the Lockheed Martin F-22, in a bid to clear the full envelope before the fighter has its first flight, planned for the end of May.

Revealing details of the integrated APGS on the eve of the F-22 roll-out, AlliedSignal says that the system has "performance margin in all areas", adding that the final altitude tests are required for "safety of flight" clearance before actual flight tests begin.

Tests are taking place in an altitude chamber at the company's Phoenix, Arizona, headquarters. The APGS plays a vital role in the operation of the F-22, being responsible for the fighter's autonomous ground-starting capability, as well as providing emergency in-flight power for the flight-control system and engine re-starting.

The system includes a 335kW (450hp) auxiliary-power unit for re-starting the engines at subsonic speeds up to 41,000ft (12,500m). It also includes a 75kW stored-energy system, which has to come on-line within 5s at any altitude, airspeed and attitude to provide flight control, hydraulic power and back-up electrical power for on-board computers.

The APGS weighs around 120kg, which "-is about 40% lighter than any previous combination", according to AlliedSignal, which claims a "30% higher power-to-weight ratio" compared to any similar installation.

As part of the F-22's planned autonomy from ground-support equipment, the APGS suite also includes an air re-charge system which provides an onboard means of re-charging air bottles. AlliedSignal is now delivering the 11 line items making up the APGS second shipset, and it expects the first system (which is now installed in the initial F-22) to be started for the first time by mid-April (see F-22 supplement, this issue.)

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