This is when an aircraft (and its occupants) experiences a force less than its weight. In an extreme maneuver in “bunt” (i. e., developing – negative g in a nose-down
curved trajectory), the centrifugal force pointing away from the center of the Earth can cancel the weight when the pilot feels weightless during the maneuver. The corner points follow the same logic of the positive load description except that the limit load of n is on the negative side, which is lower because it is not in the normal flight regime. It can occur in an aerobatic flight, in combat, or in an inadvertent situation caused by atmospheric gusts.
1. Negative High Angle of Attack (-NHA). This is the inverted scenario of +PHA explained previously. With -g, the aircraft must be in a maneuver.
2. Negative Intermediate Angle of Attack (-NIA). In +PLA, the possibility of – ve a was mentioned when the elevator is pushed down, called the “bunting” maneuver. Negative a classically occurs at inverted flight at the highest design speed, VC (coinciding with the PIA). When it reaches the maximum negative limit load of n, the aircraft takes the NIA.
3. Negative Low Angle of Attack (-NLA). At VD, an aircraft should not exceed zero g.