Line Maintenance Procedures in Aviation

Aircraft · 5 min read · Nov 14, 2022
line maintenance

Maintenance is at the core of the operations in any industry, but no one could argue that this is especially true for the aviation industry. In the end, aircraft maintenance is a top priority to guarantee the safety of the passengers and the crew at all times. Moreover, maintenance is required to comply with regulations and meet the requirements to keep aircraft airworthiness.

Now, the fact is that there are different tasks classified into different maintenance categories, and one of these categories is line maintenance.

If you want to discover what line maintenance is in aviation and the tasks that are involved in it, keep reading as we share all the details.

What is line maintenance?

A general definition of line maintenance can be “the basic level of maintenance performed on an aircraft during its operational life.”

However, an official definition provided by Part 145 regulation states that line maintenance is any maintenance task that can be performed outside of a hangar (under open skies) except for situations in which the weather deteriorates to such conditions, that a hangar becomes mandatory.

An aircraft stationed in a hangar for aircraft line maintenance procedures.

Who performs line maintenance?

This type of maintenance is typically performed by licensed mechanics at an airport’s line station. The purpose of line maintenance is to keep an aircraft in an airworthy condition and to perform routine checks and repairs. However, some line maintenance support can be provided by airline or airport personnel.

For some aircraft, the scope of line maintenance is specified in the MPD or MS (Maintenance Planning Document or Maintenance Schedule).

The same documentation will specify components which are known as LRU – Line Replaceable Units. This implies that the replacement of such components can be done during line maintenance. The engine is sometimes considered an LRU. Yet, the replacement of the engine may require a hangar facility.

Line maintenance is different from scheduled maintenance in a few key ways. First, scheduled maintenance is generally performed at regular intervals regardless of whether an aircraft is experiencing any issues. Second, scheduled maintenance is typically more comprehensive and can involve more complex procedures than line maintenance. Finally, scheduled maintenance is usually performed by the original equipment manufacturer or an independent airworthiness management organization, while line maintenance is also performed by airline or airport personnel.

Engineers performing aircraft line maintenance on an airplane stationed outdoors.

What is the difference between line maintenance and base maintenance?

Line maintenance is performed on a daily basis and involves checking and correcting any minor defects or malfunctions that may have occurred during the previous flight. This type of maintenance can be carried out at the airport where the aircraft is stationed or at any other location where it may land during its operation.

Base maintenance, on the other hand, is performed on a regular schedule and includes more extensive inspections and repairs. This type of maintenance typically takes place at a designated base or facility, where the aircraft is taken out of service for a period of time until all necessary checks and repairs are completed.

Unlike base maintenance, line maintenance focuses on immediate problems and keeping the aircraft safe for operation in the short term instead of addressing long-term issues, but still aims to maintain the overall airworthiness of the aircraft. Both types of maintenance are crucial for ensuring safe flight operations and complying with regulatory requirements provided by the local aviation authority listed by ICAO or other sizeable aviation organizations.

Aircraft maintenance tasks

Maintenance activities are usually defined by the maintenance department of the airline. The department will create maintenance programs with activities that are considered line maintenance and those considered base maintenance.

Given the complexity of each aircraft, there is usually a specific maintenance program for each type of aircraft which is why some aircraft operators look for external maintenance engineering services.

The scope of aircraft maintenance can vary depending on the size and type of aircraft, as well as the specific issue that needs to be addressed. However, there are certain types of maintenance tasks that are commonly performed on most aircraft. These tasks include:

Cabin Checks

Cabin checks are performed to ensure that all emergency equipment is in working order and that all passenger seat belts are functional. In addition, the cabin crew may use this time to perform routine cleaning and restocking activities.

Engine Checks

Engine checks are performed to ensure that all engine systems are functioning properly. This includes checking oil levels, fuel system components, and engine performance data. In some cases, engine checks may also involve visual inspections of engine components for signs of wear or damage.

Aircraft Systems Checks

Aircraft systems checks are performed to ensure that all onboard systems are functioning properly. This includes checking the status of flight controls, navigation systems, communications systems, and electrical systems. In some cases, aircraft systems checks may also involve testing individual components to ensure proper function.

Nevertheless, what line maintenance includes is generally the same for all aircraft types. Let’s see some typical tasks involved in this type of aircraft maintenance.

An aircraft mechanic performing engine checks on an aircraft.

Typical line maintenance tasks

As mentioned earlier, line maintenance covers a wide range of activities. Some typical tasks that are performed during this type of maintenance include the following:

  • Tire changes
  • Engine replacements
  • Brake replacements
  • Interior cleaning
  • Exterior washing
  • Cabin pressure checks
  • Aircraft refueling
  • Aircraft re-oiling
  • Software updates
  • Instrument calibration
  • Component replacements

Aircraft that require more extensive work is usually transferred to an off-site location for repair.

What Are The Benefits of Line Maintenance?

There are many benefits of investing in quality line maintenance services.

One of the benefits of line maintenance in aviation is cost savings. Through regular line maintenance, airlines can avoid more costly and time-consuming repairs and replacements down the road. Additionally, line maintenance allows for quicker identification and resolution of potential problems before they become larger issues.

Line maintenance also helps ensure the safety of passengers and crew on board aircraft by regularly checking and maintaining critical components such as engines, flight control systems, and navigation equipment.

Furthermore, regular line maintenance helps maintain compliance with regulatory requirements for airworthiness. This not only ensures safety but also allows airlines to continue operating without interruption or delay.

Overall, line maintenance in aviation plays a crucial role in ensuring the smooth operation and safe operation of aircraft, while also providing cost savings and aiding in regulatory compliance.

An aircraft being prepared for a flight.

Final words

Line maintenance is a vital part of keeping an aircraft in good working conditions. By performing routine checks and repairs, licensed mechanics can ensure that an aircraft remains safe and airworthy. Not only is it required by regulations, but it also helps to prevent potential accidents and malfunctions.

In addition, line maintenance can help improve efficiency and reduce downtime for aircraft operators, ultimately leading to better overall profitability for them. It is important for airline companies to have a comprehensive line maintenance program in place and to properly train their staff on proper maintenance procedures. The responsibilities of line maintenance personnel should not be taken lightly as they play a crucial role in ensuring safe flights for all passengers.

Fortunately, advancements in technology have allowed for improved methods of line maintenance, such as predictive maintenance and digitization of processes. With these new tools, both engineers and technicians can have better results from any inspection or repair.

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Jet pilot @NASA

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