What is a Maintenance Check?

 The aviation industry is highly regulated, meaning that airlines and other commercial airline companies must practice continuous inspection programs established by aviation authorities. In the United States, aircraft maintenance programs are overseen by the Federal Aviation Administration (FAA). The FAA requires each airline/operator to establish a Continuous Airworthiness Maintenance Program (CAMP). The CAMP outlines routine and detailed inspections or “checks” of aircraft they have in their fleet. Checks are important to continually perform as they keep aircraft safe and airworthy. Having such a rigorous maintenance program ensures that passengers will get to their destinations safely on an aircraft that has been fully vetted for any issues prior to leaving the airport gate!

While the FAA oversees the regulations and programs, it is up to the actual airline or operator to ensure that maintenance gets done and up to CAMP specifications. Aircraft have set checks at various intervals, often known as flight line maintenance checks and also four different types of higher-level maintenance: A, B, C, and the heaviest (D) checks.

The objective of these checks is to conduct both routine and non-routine maintenance of the aircraft. The maintenance includes scheduling the repair of known problems; replacing items after a certain air time, the number of cycles or calendar time; repairing defects discovered previously, and performing scheduled repairs.

All aircraft are different and may require maintenance checks at different times than others. This is a general overview of the types of work aviation maintenance technicians can expect on a day-to-day basis!

Line Maintenance Checks

This type of maintenance is the most routine. Sometimes called post-flight, maintenance pre-flight, service check, and overnight checks, this is the most typical maintenance service performed on aircraft. Line checks require minimal tools and are usually done at the airport gate under the “open sky.”

Line checks happen the most frequently, as they cover basic inspection checks. Commonly, aviation maintenance technicians will inspect things like wheels, brakes, and fluid levels (oil, hydraulics) during line checks.

Performing a line maintenance check ensures an aircraft is airworthy and safe to continue service. Aircraft need line maintenance every 24 to 60 hours of accumulated flight time, but it depends on the operator of the aircraft!

A Checks

The next level of checks is known as A checks. The A check is performed approximately every 400-600 flight hours, or every 200–300 flights, depending on aircraft type. A check maintenance is typically done at a hangar and can take a minimum of 10 working hours depending on the services needed. Sometimes, this maintenance is done overnight as to not interrupt the schedule that airlines keep. The frequency of this check varies by aircraft type, the flight cycle count, or the number of hours flown since the last check.

The maintenance work during A checks often covers general inspections of the interior and the aircraft hull for evidence of damage, deformation, corrosion, missing parts. Additionally, it also includes service, engine, and function checks.

Other work performed could entail things such as:

  • checking emergency lights
  • lubricating nose gear retract actuator
  • checking parking brake accumulator pressure

B Checks

Next, B checks are often completed during the A check phase, as airlines and operators have phased out B checks. For airlines and operators to efficiently maintain, repair, and overhaul an aircraft, some B check tasks have been absorbed into A check phases. This helps by reducing aircraft downtime, reducing time maintenance technicians work on the aircraft, improving maintenance scheduling, and implementing better usage of resources such as hangars and test equipment.

Aviation maintenance professionals perform B maintenance checks approximately every 6-8 months. It takes about 160-180 labor hours, depending on the aircraft, and can be completed within 1–3 days at an airport hangar.

Typical work completed during B checks are tasks such as checking alignment and torquing of the nose landing gear spotlight or inspecting the wheel well hydraulic tubing for condition, corrosion, and fluid leakage.

C Checks

C and D checks typically fall under “heavy maintenance,” and are much more extensive than the B check. The C check requires an aviation maintenance technician to perform a deep inspection of a majority of the aircraft’s parts.  Also, the C maintenance check can often take the aircraft out of service for 1–2 weeks.

This type of check often requires an aircraft to stay at a maintenance facility for the necessary space/tools/maintenance technician working hours/materials. Up to 6,000 maintenance hours are typically needed for C checks.

Aviation maintenance technicians will perform certain tasks during C checks, such as:

  • examination of structures (load-bearing components on the fuselage and wings) and functions for corrosion and damage
  • checking the operation of the DC bus tie control unit
  • in-depth lubrication of all fittings and cables

There are different levels of C checks depending on the type of aircraft, much like how A checks incorporate B check tasks! For example, a schedule might have aviation maintenance technicians performing C1 check tasks on a certain day and then the next day continuing with C2 and so on.

D Checks 

Lastly, the so-called “heavy maintenance visit” occurs every 6-10 years depending on the aircraft. D checks are comprehensive inspections and repairs of the entire aircraft and can mean taking apart the aircraft to inspect for damage and corrosion. The process can take upwards of 30,000 to 50,000 labor hours over a period of four to six weeks.

With the entire aircraft stripped down and equipment removed, airlines often decide to refurbish aircrafts’ interiors and upgrade them altogether during D checks.

Because of the nature and the cost of a D check, most airlines plan D checks years in advance. Oh, and the cost of the entire process can cost upwards of a few million dollars!

There comes a certain point where airlines realize that the cost of repair is more than the actual cost of the aircraft. This usually happens after two or three D checks.

Routine Maintenance Checks and You 

There is a strict system for aircraft to be properly maintained, repaired, overhauled, and inspected as time goes on. The Federal Aviation Administration sets this system in place, and it is up to airlines and other aviation operators to implement the system and ensure it is being followed. Above all, preventing damage to aircraft and working to keep that aircraft flying safely is what it’s all about to be an aviation maintenance technician!

Additionally, it is important to view this list as a general and brief overview of the type of maintenance checks performed by technicians. Each airline/operator is different, as is each aircraft.

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