THE LOCKHEED Martin/ Boeing Darkstar long-endurance unmanned air vehicle (UAV) will not be flown before May 1997, to enable the US team to conduct an in-depth audit of all hardware and software.

Repairs made since the April crash will be verified in an informal critical-design review due to take place in September-October, say project officials.

The Pentagon blames the 22 April crash on changes made in flight-control software and take-off technique following the first flight.

The Darkstar prototype was extensively damaged after it pitched up, stalled and crashed moments after taking off from a runway at Edwards AFB, California, on its second test flight. Salvageable parts were recovered.

The stealth UAV had undergone a successful 20min initial test flight on 29 March. Changes were made to the flight-control software and the take-off technique between its maiden and second flights.

"The mishap is directly traceable to deficiencies in the modelling and simulation of the flight vehicle," says the Pentagon.

It adds that the contractor team is conducting analyses and revising simulations to allow it to create more accurate models of expected flight characteristics in all of the UAV's flight regimes.Flight testing will not resume until the problems are rectified. More comprehensive operator training and better abort procedures have also been ordered.

A second flying prototype is now undergoing integration and development testing. The project calls for fabrication of two additional air vehicles to be used for flight demonstrations until 1999.

Source: Flight International