Aircraft maintenance checks

Aircraft Maintenance is a maintenance operation - carried out on the aircraft and its components in order to keep the aircraft safe and ready for their daily operations - in compliance with the regulation for the testing of aeronautical equipment ( LuftGerPV ). The work includes a wide range of penetration depths of the short-term repairs to the ramp ( airport apron ) during flight operation to complete disassembly and reassembly of the complete aircraft in the so-called D-Check. The term is not limited to the complete aircraft, but is also for subsystems, such as engines or attachments, such as generators, etc. out.

Definition of aircraft maintenance

As a generic term in aircraft maintenance, the term maintenance. The maintenance of aircraft includes the following four terms:

  • Identify and assess the actual state
  • Restoring the required condition
  • Installation of the modifications required by the Authority,
  • If necessary, the manufacturer's recommended modifications.

For example, the following measures during maintenance of aircraft are performed: Cleaning, preserving, lubricating, replenishing supplies, replacement and subsequent or setting.


With its highly complex logistics processes, a separate industry has developed with over $ 36 billion in sales worldwide, led in Germany by the maintenance subsidiary of Deutsche Lufthansa, Lufthansa Technik AG. Other European companies are Air Berlin Technik GmbH, MTU Maintenance, Air France Industries KLM Engineering & Maintenance, Iberia, TAP Air Portugal, Finnair Technical Services and a number of independent companies ( Jetalliance Technical Services GmbH, SR Technics Group, Jet Aviation, EIS Aircraft GmbH, Atlas Air Service AG).

Maintenance of commercial aircraft

The maintenance of commercial aircraft, particularly commercial aircraft, according to 2042/2003 ( Part 145 ) regulates stricter limits Annex II of the EU Regulation and includes each important component time or flight hours dependent events, which can be grouped in blocks. The work will be divided into routine, Nonroutine and modification work.

The maintenance and repair concept for a commercial airliner consists of maintenance and repair events, so-called Letter Checks ( A-, B-, C- and D-Check ). A- checks are performed most frequently, the B- check example every six months, a C-check is performed every two years and takes a few days. The D -Check is the longest event, it stands at about every 10 years.

Routine work can be planned in advance, shall be repeated at certain intervals according to MPD (maintenance planning document) (examples: various filter change / filter cleaning, replacement of wearing parts, including: hangaring / Dehangaring, carrying out inspections and controls).

Nonroutinearbeiten include repairing the detected by the inspections and monitoring findings ( findings: deviation of the actual state of the aircraft ) against the target state ( Structure Repair Manual, Aircraft Maintenance Manual, construction drawings, ...). Nonroutinearbeiten are not / only difficult to plan.

The work package modification involves performing conversions, prescribed by the aircraft manufacturer or the Authority inspections, modifications, enhancements.

Approved maintenance

All checks are carried out by a maintenance program approved by the Authority. Each operator is obliged to have approved such a maintenance program at its respective Authority. Such a maintenance program is always related to a specific aircraft model. It can be created by the operator or service provider, or shopped at the aircraft manufacturer. The framework to this is the maintenance manual, which is supplied by the aircraft manufacturer. It represents a recommendation, but there are still various other requirements to be considered.

The intervals of the checks therefore differ considerably from aircraft type to aircraft type and also partly from airline to airline, depending on the working by which maintenance program. The intervals specified in the maintenance program must be complied with strictly, triggered actions threaten by the Civil Aviation Authority.

A-Check ( Minor Check)

The A- Check is a maintenance event with routine review of technical systems that are important for flight operations, as well as the thorough maintenance of the cabin. An A -Check is payable depending on the aircraft type all 250 to 650 flight hours, or about every two months.

A- checks are performed most frequently; the scope and the " penetration " of the work to be undertaken is within one night ( in the hangar ) performed without removing the aircraft from its flight operations.

B -Check

The B -Check is a supplement to A-Check and usually take place every 3-5 months instead of, or about every 1000 flight hours. This check, however, there only for the types of aircraft Boeing 737-200 and Boeing 747-200.

There are carried out operations, which engage deeper into the airframe, and the systems. The duration of this check is approximately 150 hours, and the aircraft is thus removed from the flight operations for at least 12 h.

C-check (Major Check)

C-check refers to the detailed inspection of the aircraft structure and a thorough testing of the systems, this is for the most part the fairing removed and expanded all seats. A C-check is depending on aircraft type place every 15 to 18 months, the aircraft will remain for about one to two weeks in the hangar. Such a C-check includes approximately 5000 hours of work.

IL -Check

Deep inspection of all parts of the structure, fuselage and wings. Review and, where appropriate, repair of the equipment (electronics, hydraulics). Installation of product improvements the manufacturer complete overhaul of the cab. An IL -Check will be held every 48 months in the rule.


The D-check is equivalent to a major overhaul and is the most intense, longest and most expensive maintenance event. It takes place about every six to ten years. ( In a 747-400 after 55,000 flight hours. ) The aircraft is exposed to the ground structure and must then be repainted if necessary. During the D- checks fall to 30,000 to 50,000 hours of work. A D-Check takes about four to six weeks and can cost several million euros.

MRO Consultants

There are companies who specialize in advising airlines on this issue. These are called MRO Consultants referred. MRO is now trying for Maintenance, Repair, Overhaul.

Smaller airlines often use these services in order to control their interests in the overhaul of the aircraft or its components. Some of these consultancies operate worldwide, such as Bureau Veritas, others are in comparison to this small but dedicated specifically to the aviation sector, such as, based in London (UK), Ann Arbor ( U.S.), plus the boutique aviation strategy consulting ADAVCO in Germany.