Under what condition can chocks be removed from an aircraft on the ramp?

Chocks are crucial for preventing an aircraft from rolling while it is stationary, especially on a ramp where there might be uneven surfaces or slopes. The removal of chocks is governed by safety protocols that are designed to protect both the aircraft and ground personnel.

The correct condition for removing chocks is when a pushback tractor is connected and the brakes of the aircraft are set. This scenario provides a controlled environment where the aircraft can be moved safely. The pushback tractor serves as a means of propulsion, and having the brakes set ensures that the aircraft cannot roll away unintentionally while the chocks are being removed.

In contrast, if the aircraft is powered down, it does not guarantee that it is held securely in place without chocks being in place. Servicing the aircraft does not negate the risk of movement, and merely having approval from the pilot does not replace the necessity of ensuring that the aircraft is secured effectively against unintended movement. Thus, the presence of a pushback tractor coupled with set brakes is the most definitive condition for safely removing chocks from an aircraft on the ramp.