For example, this check requires aviation maintenance technicians to inspect things like wheels, brakes, and fluid levels (oil, fuel, hydraulics). Next, the A, B, C, and D checks are usually performed after a certain number of flight hours. They require a set number of working hours to complete, so the aircraft will not be available for service during these types of checks. As the aircraft logs more in-service time and the age of the aircraft progresses, heavier checks, such as a D check, will be necessary. For instance, D checks occur every 6-10 years depending on the aircraft’s usage and age. D checks are comprehensive inspections and repairs of the entire aircraft and can mean taking apart the aircraft to inspect for damage and corrosion.
