F-22A #91-4008 makes the first GBU-39 SDB drop at supersonic speed 7/11/08 Photo: Lockheed / Kevin Robertson

7/17/2008 - EDWARDS AIR FORCE BASE, CA -- On July 11, the 411th Flight Test Squadron passed a milestone as an F-22 Raptor travelling at supersonic speed dropped a GBU-39 Small Diameter Bomb for the first time.

The first supersonic SDB drop was part of a safe separation test currently being performed to integrate the bomb with the F-22.

The SDB is a 250-pound class precision guided munition capable of destroying high-priority stationary targets from Air Force fighters and bombers from stand-off distances.

"An SDB has never been dropped from a supersonic aircraft," said Maj. Michael Starr, 411th FLTS test pilot. "Supersonic separation testing will give the F-22 the ability to drop the SDB at supersonic speeds, which synergistically enhances the Raptor's air-to-air mission."

This was a critical step in achieving the goal of employing a "fully operational small-diameter bomb," said Capt. Chris Smith, 411th FLTS flight test engineer. The 411th FLTS is planning on performing more supersonic drops as part of this testing.

For safety purposes, the team based its test on a build-up approach, gradually increasing the aircraft speed and altitude.

"At first, we had to make sure the aircraft could carry the small-diameter bombs," Captain Smith said. "We performed ground vibration testing to ensure that any conditions wouldn't excite any structural modes of the F-22 and the bomb. We also did three rounds of pit tests, where we placed an F-22 over a specifically designed stores separation pit and performed numerous drops to verify safe separation of the bomb from the aircraft and to ensure we did not structurally overload the aircraft."

Performing ground testing ensured everything was in proper order before performing separation testing in the air, said Nicholas Chung, 411th FLTS air-ground weapons integration engineer.

"We started dropping small-diameter bombs from the F-22 at a speed of 0.8 Mach," Mr. Chung said. "We also performed eight subsonic drops prior to this milestone."

Currently, the F-15E Strike Eagle is the only aircraft outfitted with the SDB weapon system. Meanwhile, the F-22 carries two 1,000-pound Joint Direct Attack Munitions for its global strike role.

"Because of the size of the small-diameter bomb, the F-22 can carry more munitions at a time," Mr. Chung said. "Now, we are looking at carrying eight SDBs compared to just two JDAMs. This will allow the aircraft to strike up to eight targets at a time."

The team is performing the testing at Edwards because it is the only Air Force facility that performs developmental flight test on F-22s.

"Edwards has the resources in terms of both assets and test expertise," Mr. Chung said. "We really have an emphasis not just on the technical aspect but also the safety aspect of the testing."

Following a series of additional supersonic drops and after the 411th FLTS determines safe separation of the bomb from the aircraft, testers will begin dropping guided weapons, Mr. Chung said. This is to determine not only safe separation of the SDB from the aircraft, but also to see if pilots are able to guide it to the target.

"This capability is essential to give the F-22 further combat capability for the Global War on Terror," Major Starr said.

"Through Herculean effort and incredible skill, the (411th FLTS) engineers, flight test engineers, civilians and government contractors did an unparalleled job showcasing the fact that the F-22 Raptor is, and will remain, the world's most dominant fighter aircraft."

Source: USAF Edwards AFB Press Release by Senior Airman Julius Delos Reyes