Which type of maintenance is typically done after discovering deficiencies during operation?

Unscheduled maintenance is performed when an issue or deficiency is identified during operation, rather than according to a predetermined maintenance schedule. This type of maintenance addresses immediate concerns and repairs necessary to maintain the aircraft's safety and operational readiness.

For instance, if a pilot reports an anomaly or if maintenance personnel discover a fault during routine checks, unscheduled maintenance is triggered to investigate and rectify the problem promptly. This ensures that the aircraft continues to meet safety standards and can be operated reliably.

Scheduled maintenance, on the other hand, is based on a calendar or flight hour schedule and does not typically occur in response to immediate operational deficiencies. Acceptance inspection involves evaluating an aircraft's condition following its completion of manufacturing or major repairs, rather than addressing operational issues. A turnaround inspection generally refers to a brief check of the aircraft before it departs on its next scheduled flight, primarily to ensure it is ready for takeoff rather than to address deficiencies identified during operation.