Attitude Recovery System Installed for G500 Flight Testing
As more advanced testing has begun for the all-new Gulfstream G500, flight-test engineers have equipped and tested the aircraft with a rear-deploy attitude recovery system parachute.
A parachute would never be standard issue for a non-test aircraft, but it is routine when conducting aerodynamic stall testing, which can be hazardous. Gulfstream experimental test pilots will deliberately put the aircraft into an aerodynamic stall to determine the angle of attack at which the aircraft stalls at any given flight condition.
An angle of attack protection system will then be added to the production aircraft to advise of—and prevent—an imminent stall.
An aerodynamic stall occurs when the wing loses optimal flow of air. Known as the stall angle of attack, it is the point at which the wing loses lift and is not able to maintain flight.
To understand the dynamics at work, think about a bicycle in motion. It needs forward movement to stay upright. If the bike slows too much, it can’t stay upright. Just before it falls, the bike and rider will start to wobble. In broad terms, the same thing happens to airplanes. If you slow down an airplane gradually near its stall speed, it will start to buffet; if the pilot does not add thrust or lower the nose to recover optimal flow over the wing, the airplane will stall.
While testing for aerodynamic stall limits, there is the risk of a deep stall, which is more difficult to correct. When in a deep stall, the pilot may not be able to lower the nose and regain airflow over the wings. If the test pilot cannot recover control through pilot input to the flight controls, he has the option of deploying the stall chute. The chute deploys out the back of the aircraft, creating drag that will lower the aircraft’s nose, allowing the jet to gain airspeed and recover from the stall. The crew can then jettison the chute, raise the nose, regain altitude and return to straight and level flight.