How Things Work: Thrust Vectoring
In a tight spot, you need zoom to maneuver.
- By Jim Mathews
- Air & Space magazine, July 2008
NASA Dryden Flight Research Center
(Page 2 of 2)
Theorists say air combat could be changed by the introduction of some maneuvers unique to thrust vectoring. A high angle-of-attack descending spiral is one. At a high angle of attack, a rudder loses its effectiveness, and being able to rely on thrust vectoring would let a pilot enter what’s essentially a controlled flat spin, yawing the airplane around to aim at a target without worrying about the rudder. The pilot also gets extra maneuverability at high altitudes, says Wagemann, “where the air density is so low that the flight control surfaces become significantly degraded.” Then there’s the super-tight J-turn, or even a modified hammerhead, in which an airplane appears to briefly fly backward.
One common misconception about thrust vectoring involves the flashy cobra maneuver, also known as Pugachev’s cobra, after Russian pilot Viktor Pugachev, who first wowed crowds with it in a Sukhoi Su-27 at the 1989 Paris Air Show. The maneuver is not an example of thrust vectoring. If the pilot is skilled enough, he can do the cobra in nearly any type of U.S. jet fighter. In essence, the pilot abruptly pulls the control yoke full aft while flying around 300 knots—about 345 mph—and thus pitches the nose up dramatically so the airplane is nearly standing on its tail. Just as abruptly, the pilot pushes the stick forward, dropping the nose back down. When the maneuver is flown correctly, with little change in altitude, the effect is like the striking of a cobra’s head.
Right now, the F-22A and the Russian Sukhoi Su-37 and Su-30MKI (flying with the Indian air force) are the only fighter aircraft with two-dimensional thrust vectoring nozzles.
More sophisticated designs, which have yet to fly beyond the testing stage, feature nozzle flaps that can move 17 to 20 degrees in nearly any direction, resulting in maneuvers around both the pitch and yaw axes. Both major U.S. fighter engine makers, Pratt & Whitney and General Electric, tested multi-axis vectored nozzles about a decade ago for an Air Force demonstration program.
Until thrust vectoring becomes more widespread, few will enjoy that extra edge—and that’s just fine with U.S. pilots. “Thrust vectoring provides such a significant advantage in the visual maneuvering arena that I rarely find myself in a defensive position,” says Wagemann. “When we start defensive, for training, you are almost always able to transition to offensive without getting shot.”