CHANGES IN SOFTWARE, TAKEOFF PLAN BLAMED IN DARKSTAR CRASH.

Byline: Jim Skeen Daily News Staff Writer

A pilotless reconnaissance aircraft called DarkStar crashed because of changes made to the flight control software and takeoff technique, Pentagon officials said Tuesday.

The changes were made after DarkStar's first flight March 29. During the takeoff roll in that flight, the aircraft's main landing gear lifted off prematurely, and the aircraft ``wheelbarrowed'' on its nose wheel down the runway. The rest of the flight went smoothly, officials said.

``Analysis of the accident data by the government and contractor team have confirmed that the primary cause of the accident was changes to the flight control software and takeoff technique,'' a Pentagon statement says. ``The investigation found that the mishap is directly traceable to deficiencies in the system modeling and simulation performed as part of the data analysis of the first flight.''

In a film of the crash released by the Pentagon, DarkStar is seen porpoising as it makes its takeoff roll. The aircraft flew to about 150 feet above the Edwards runway, pitched nose-up to about a 90-degree angle, stalled, rolled to the left and slammed into the ground, exploding on impact.

``Several modifications to the system software and some minor modifications to the hardware will be made to overcome these problems,'' notes a statement from DarkStar's contractor, Lockheed Martin ``Skunk Works.'' ``Planning for resumption of the flight test program and incorporation of design changes is under way.''

In a June 28 letter to Congress, Air Force Maj. Gen. Kenneth Israel, director of the Defense Airborne Reconnaissance Office, says a replacement for the aircraft will cost $17 million.

It will cost an added $22 million to prepare a second DarkStar airframe for flight and accelerate the construction of a third aircraft.

Wide, flat and tailless, with a 69-foot wing span and a blunt fuselage only 15 feet long by 5 feet high, the 8,600-pound DarkStar was powered by an engine similar to the one used in the Cessna Citation business jet and capable of propelling the aircraft to altitudes above 45,000 feet.

DarkStar was designed to fly pre-programmed flights, conducting its entire mission under computer control without additional commands from the ground. However, it was flying under the guidance of controllers on the ground when it crashed, officials said.

DarkStar was developed under a $124 million contract covering the development and production of two aircraft. The program is being funded by the Defense Airborne Reconnaissance Office and the Defense Advanced Research Projects Agency.

DarkStar was designed to be a stealthy, high-altitude aircraft able to linger over a battlefield for more than eight hours and cover more than 14,000 square miles. The aircraft was designed to provide video and other information, day or night, to battlefield commanders.

Half of the aircraft's construction was done in Seattle, and the other half by Lockheed Martin's Skunk Works in Palmdale. Boeing Defense and Space Group built the aircraft's wing and is responsible for the avionics integration and the autonomous flight system.