Aircraft maintenance checks refer to the periodic inspections that every commercial and civil aircraft must go through after a certain number of flying hours or time of use. Military aircraft may or may not have the same types of checks as commercial, but they must have their own maintenance programs as well. The aviation industry is extremely regulated, and commercial operators must comply with the inspection programs of authorities like the Federal Aviation Administration, Transport Canada, and the European Aviation Safety Agency.
Every operator must establish a Continuous Airworthiness Maintenance Program (CAMP) in its operations, including routine and detailed inspections of their air assets. The FAA institutes a series of inspections known as checks, classified as A, B, C, and D. A and B are relatively minor checks, while C and D are more exhaustive. Aircraft operators can conduct lighter checks in their own facilities, but must perform heavier checks at the site of a certified maintenance, repair, and overhaul (MRO) company.
A-checks are performed every 400-600 flight hours or 200-300 cycles (a cycle is one takeoff and landing). This inspection takes roughly 50-70 man hours, and requires an aircraft to remain on the ground for about ten hours, depending on its condition.
B-checks are conducted every six to eight months, and requires 160 to 180 man hours, depending on the aircraft’s type and condition. B-checks typically take one to three days.
C-checks are performed every 20 to 24 months, or after a specific number of manufacturer-set flight hours. They are more expensive than A and B-checks, involving inspections of large numbers of aircraft components, and require an aircraft to stay at an MRO site for at least two weeks and up to 6,000 man hours of work.
3C is an intermediate layover, and refers to light checks for corrosion or deterioration of specific parts of an airframe. Operators also take the 3C check as a chance to perform cabin upgrades (like new avionics, carpeting, etc), or incorporate the 3C into their D-checks.
The D-check is the most intensive type of check for aircraft. Also called a heavy maintenance visit, the D-check is performed every 6 to 10 years, and can see the entire aircraft disassembled for inspection and repair. The aircraft must be stationed at a spacious maintenance base, can take up to two months, requires 50,000 man-hours of work, and can cost about 1 million dollars to complete. Most operators choose to retire their aircraft at this point, as the cost of repairs exceeds the value of the aircraft.