What is a primary requirement for operating thrust reversers on paved surfaces?

The primary requirement for operating thrust reversers on paved surfaces is that they must not be deployed in flight. This is because deploying thrust reversers while airborne can significantly alter the aerodynamic characteristics of the aircraft, potentially leading to a loss of control. Thrust reversers are designed to redirect engine thrust forward to assist in braking during landing or on the ground, but they should only be used when the aircraft is on the runway or taxiway.

This safety guideline ensures that aircraft maintain optimal performance and stability during flight operations. The restriction on deploying thrust reversers in flight is critical for pilot training and adherence to aviation safety protocols.