Defence

A key new weapon for the Lockheed Martin F-22 Raptor has started a new series of tests despite a recent in-flight crash scare.

The Boeing GBU-39 Small Diameter Bomb (SDB) began separation tests on the F-22 in early September after more than a year of sometimes difficult work to integrate the weapon in the weapons bay and carry out airborne captive carry tests, Maj Jack Fischer, a USAF test pilot, told the Society of Experimental Test Pilots' annual convention.

Flight tests so far have produced a few in-flight problems, including one particular event that "could have been very bad", Fischer said.

In that incident, an F-22 suffered a brief, dual-engine flameout while performing a negative-g, 360 degree roll with eight SDBs loaded in the weapons bay. The flameout occurred because the aircraft entered the manoeuvre with an incorrect trim setting.

Although the engines restarted before the pilot was even aware of the problem, the momentary power loss dropped the telemetry signals to the control room on the ground.

The control staff lost contact "with the aircraft pointed down toward the water at a very low altitude", said Capt Harris Hall, a programme official. "For a time, we thought the aircraft was lost."

However, the engines were restarted almost immediately and the pilot remained in control of the aircraft, he said. The pilot landed at Edwards AFB, California, without incident. The dual-engine flameout was not discovered until flight engineers reviewed performance data from the flight.

Integrating the 250lb (113kg)-class SDB is key to making the F-22 a more effective air-to-ground weapons platform, displacing two 2,000lb Joint Direct Attack Munitions with eight, "extreme stand-off" guided bombs in the internal weapons bay, Fischer said.