In Depth

The F-35’s High Angle of Attack Explained

July 12, 2016

For every student who doesn’t care much for Geometry, there’s a fighter pilot who appreciates its importance, especially in aerial combat. Angles and energy management determine speed and position when maneuvering for the “kill shot”. They determine the difference between the ‘quick’ and the ‘dead’ once the fight is engaged.

Flying at high angles of attack (AoA) - also known as “High Alpha” - fighter aircraft gain enhanced nose-pointing capability, allowing pilots to find, fix and target enemy aircraft. Being able to point the nose rapidly is how you outmaneuver the enemy, ‘lock on’ to them with your radar and heat-seeking missiles and take the decisive shot.

AoA refers to the angle between an aircraft wing’s chord line, the imaginary straight line between the wing’s leading and trailing edges, and the aircraft’s flight path. It’s not to be confused with attitude, the jet’s relation to the Earth, which is seldom the same as AoA. When the angle is small, the aircraft is at a low angle of attack. When larger, the aircraft is at a high AoA.

The F-35’s high AoA testing pushed the jet to the AoA limit of 50 degrees nose high and included beyond both positive and negative maximum command limits. Test pilots flying in the stealthy ‘clean’ wing configuration also tested it with externally-mounted air-to-air pylons and missiles, and also with open weapons bay doors, all creating additional slowing speed drag on the aircraft. Test pilots took the aircraft beyond this limit to evaluate its characteristics in recovering from out-of-control flight conditions.

While AoA is critical for maneuver, the days of actually ‘closing with the target’, rolling and turning to get behind your opponent, are becoming dated. That’s why the F-22 and F-35 were made stealthy: to give US and allied pilots the ‘first-shot/first-kill’ advantage, shooting from beyond visual range (BVR), without being detected. Since the 1991 Persian Gulf War, a steadily increasing number of air-to-air victories have been achieved BVR; the last aerial gun-to-gun kill was recorded in 1988.

With the F-35’s multi-source onboard sensor data coming into the cockpit, coupled with the F-35’s Distributed Aperture System (DAS) giving the pilot 360-degree visibility, it is pretty tough to surprise an F-35 pilot in aerial engagement. Military 5th generation tactics emphasize formations, multiplying the number of sensors looking for threats. These inputs merge with info from off-board sensors on satellites and the network of other Intelligence, Surveillance and Reconnaissance (ISR) aircraft to build a comprehensive, ‘fused’ picture of the battlespace.

The F-35 was also designed to turn at nine Gs, with a full load of internally-stored fuel and weapons, far outclassing any enemy jet with their externally-mounted missiles and fuel tanks. The F-35 is designed to be comparable to current 4th Generation tactical fighters, such as the F-16, F/A-18, and F-15, in terms of maneuverability, but the Lightning II’s design is optimized for stealth, allowing it to operate in contested airspace environments where they could not survive latest current and emerging threats.

"The F-35 is very capable in the Within Visual Range (WVR) environment, and its high AOA maneuverability is one of the tools available to maximize its lethality and survivability,” says

Capt Joshua Reddis, 58th Fighter Squadron F-35A pilot at the 33rd Fighter Wing, Eglin AFB, Florida.

“However, the F-35's greatest strength is its ability to acquire and fuse information permitting decision-making and lethal employment at range, prior to being detected by the adversary in question,” he added.

“Whether you are talking about Air-to-Air or Surface-to-Air entities, the ability to avoid or destroy threats prior to them becoming a factor renders high G and high AOA maneuvering unnecessary, even if the airframe itself performs well in those envelopes,” Capt Reddis explained.

“The bottom line is that the F-35 is designed to be highly survivable and extremely lethal in a high threat, near-peer environment. Nevertheless, those same features are equally applicable to a low threat conflict where it can load additional external ordnance and bring its sophisticated information management capabilities to the current fight."

The F-35’s combination of stealth, electronic warfare, cyber capabilities, and almost as a last resort – agility – will seriously degrade each step in an enemy’s ability to detect, track, shoot at, and ultimately get close to threaten an F-35.