Final answer:
The question asked about the minimum number of operational yaw dampers required for flight and the actions to take if a yaw damper fails in flight.
Step-by-step explanation:
The question pertains to the operational requirements of an airplane's yaw damper system for acceptance of flight. The yaw damper is a critical component of an aircraft's control system, which helps to reduce the yaw oscillation or 'Dutch roll' primarily in twin-engine airplanes.
However, without the exact phrase that should complete the sentence, the response would typically be based on standard regulations or the specific Aircraft Maintenance Manual (AMM) for the airplane in question.
In general, some commercial aircraft are designed to be able to fly safely with one yaw damper inoperative. The exact number of operational yaw dampers required for flight acceptance can vary depending on the aircraft make and model, as well as the regulations set by aviation authorities.
If a yaw damper fails in flight, standard procedure usually involves following specific checklist procedures for yaw damper failure, which are provided in the airplane's flight manual. It may also include restrictions on flight operations such as prohibition of certain maneuvers or automated flight modes.