General Authority of Civil Aviation (GACA) Aeronautical Information Publication (AIP) Practice Exam

At which point is the trim inhibited in the nose down direction during overspeed protection?

1. At VMO/MMO

2. Below stall speed

3. During takeoff

4. While cruising

The correct answer is: At VMO/MMO

The correct choice is based on the operational parameters of an aircraft’s speed limitations. The trim is inhibited in the nose down direction at VMO (Maximum Operating Velocity) and MMO (Mach Maximum Operating Limit) to prevent the aircraft from exceeding these critical speed thresholds. When an aircraft approaches these limits, it may be at risk of a dangerous overspeed condition, where aerodynamic forces could lead to structural stress or failure. By inhibiting the trim in the nose down direction, the flight control system actively prevents further descent of the nose, which could cause an increase in speed and exacerbate the risk of overspeed. On the other hand, below stall speed, during takeoff, or while cruising does not present the same level of criticality regarding speed limits as at VMO/MMO, and therefore, trim may not be inhibited in those situations. The primary concern for flight safety is maintained effectively by implementing this speed-related trim inhibition at the maximum operating speeds.