F-22 moves into next phase of testing

F-22 moves into next phase of testing

Released: 13 Aug 1999

by Bobbie Mixon
Aeronautical Systems Center Public Affairs

WRIGHT-PATTERSON AIR FORCE BASE, Ohio (AFPN) -- The F-22 Raptor, managed at Aeronautical Systems Center here, successfully met another test milestone recently by flying beyond 26 degrees angle of attack in a 2.5-hour sortie over Edwards Air Force Base, Calif.

The flight marked the beginning of the next phase of testing for the next-generation air superiority fighter -- a rigorous regime of high angle-of-attack flight profiles.

Simply speaking, angle of attack is not how steeply a plane dives to deliver bombs on target. Rather, it is a measurement of the angle between the wing of a plane and the flow of air as it flies through the air. As an airplane pitches up, the angle of attack increases.

High angle-of-attack, or high-alpha, testing for the F-22 is necessary to verify the extent of its capabilities in the areas of agility and maneuverability. The Raptor is the world's first production fighter designed to maneuver "with abandon" at high angles of attack. The testing, conducted at the Air Force Flight Test Center at Edwards, requires the aircraft to perform controlled flight at very slow speeds.

"The aircraft is in full 'battle dress' for the assault on high (angle-of-attack) testing," said Brig. Gen. Michael Mushala, F-22 program director here. "The flight test team has worked extremely hard to position the Raptor for this important next phase of testing."

The second flyable F-22, Raptor 02, has been specially equipped to accomplish the high alpha test missions and enter test profiles that no other fighter can safely enter.

The Air Force's current air superiority fighter, the F-15 Eagle, can only fly at about 30 degrees angle of attack. The F-22 will be tested at more than twice that, and already has flown at 36 degrees angle of attack.

Aircraft maintenance crews at the F-22's Combined Test Force at Edwards installed a stabilization recovery chute on Raptor 02 in April. The chute was installed as a precautionary measure during the testing when the aircraft is flying at very slow speeds and at high angles of attack.

The chute consists of a structure that can be removed easily when it is not needed for a particular flight profile. Should an unforeseen flight condition develop, the pilot deploys the parachute manually. The pilot's command also jettisons the parachute after control is regained.

While modeling and simulation indicate that the F-22 can safely perform the specified flight profiles, the chute will lessen risk by providing an additional safety net. In addition, the F-22's two Pratt & Whitney F119-PW-100 engines have demonstrated sufficient stall margin, giving program managers further confidence that the high angle of attack testing can be accomplished.

Over the next few months, the F-22 will be tested throughout its entire high angle of attack flight envelope. The aircraft is being purchased by the Air Force to replace the aging F-15 air superiority fighter. (Courtesy of Air Force Materiel Command News Service)