This check occurs approximately every 6-10 years.

The D check, sometimes known as a 'heavy maintenance visit' (HMV), is by far the most comprehensive and demanding check for an airplane. As component reliability has improved, some MROs now spread the workload across several C checks, or incorporate this 3C check into D checks instead. This shortens the time the aircraft is out of service, by performing two distinct tasks simultaneously. new seats, entertainment systems, carpeting. The 3C check may also be used as the opportunity for cabin upgrades, e.g. Some authorities use a type of check, known as a 3C check or Intermediate Layover (IL), which typically includes light structural maintenance, including checks for corrosion, or on specific high-load parts of the airframe.

The effort needed to complete a C check is up to 6,000 man-hours. It also requires more space than A and B checks, therefore, it is usually carried out in a hangar at a maintenance base. The aircraft must not leave the maintenance site until it is completed. This check puts the aircraft out of service for 1–2 weeks. This maintenance check is much more extensive than the B check, requiring a large majority of the aircraft's components to be inspected. The C check is performed approximately every 20–24 months, or a specific number of actual flight hours (FH), or as defined by the manufacturer. checks A-1 through A-10 complete all the B check items. B checks are increasingly incorporated into successive A checks, i.e. A similar occurrence schedule applies to the B check as to the A check. It takes about 160-180 man-hours, depending on the aircraft, and is usually completed within 1–3 days at an airport hangar. The B check is performed approximately every 6-8 months.

The occurrence can be delayed by the airline if certain predetermined conditions are met. The actual occurrence of this check varies by aircraft type, the flight cycle count, or the number of hours flown since the last check. The A check takes a minimum of 10 man-hours. It needs about 50-70 man-hours, and is usually performed in an airport hangar. The A check is performed approximately every 400-600 flight hours, or every 200–300 flights, depending on aircraft type. Aircraft operators may perform some work at their own facilities, but often checks, and especially the heavier checks, take place at maintenance, repair and overhaul (MRO) company sites. A and B checks are lighter checks, while C and D are considered heavier checks. This allows for more flexibility in the scheduling of maintenance to minimize aircraft downtime.Īirlines and airworthiness authorities casually refer to the detailed inspections as 'checks', commonly one of the following: A check, B check, C check, or D check. Modern aircraft with MSG-3-derived maintenance programs employ usage parameters -such as flight hours, calendar time, or flight cycles-for each required maintenance task included in the MRBR. The MRBR is an approved set of aircraft initial maintenance requirements as prescribed by the Appendix H to para. In the United States the FAA directs that initial aircraft maintenance requirements be generated for each aircraft type in a Maintenance Review Board Report (MRBR) based on the analysis performed as outlined in ATA 'MSG-3 Operator/Manufacturer Scheduled Maintenance Development' document (MSG-3 is for Maintenance Steering Group – 3rd Task Force). The CAMP includes both routine and detailed inspections. Each operator prepares a Continuous Airworthiness Maintenance Program (CAMP) under its Operations Specifications or 'OpSpecs'. Airlines and other commercial operators of large, or turbine-powered, aircraft follow a continuous inspection program approved by the Federal Aviation Administration (FAA) in the United States, or by other airworthiness authorities such as the Transport Canada Civil Aviation Directorate (TCCA), or the European Aviation Safety Agency (EASA).

Aircraft maintenance