August 24, 2016

Aircraft Maintenance Philosophy


While deciding the scope of the maintenance to be applied in the airplanes a balance is sought between the measures established on maintaining the security at a maximum level and the management approach established on maintaining the efficiency at a maximum level. Accordingly, scope of the maintenance is established on the precision of the balance between these two poles.

The said precision becomes clearer when adapted to our passenger cars. Considering that we operate our vehicles not for our own personal usage but with the income we obtain from the passengers we carry, the subject gets a little closer to the philosophy of maintenance. To earn money, we want to continuously operate our vehicle. We want the expenses required for the necessary maintenance to be at a minimum level or if possible we do not want any maintenance to be required. In case of any failure, we want it to be detected immediately and eliminated quickly. We want little consumption of fuel. We want to carry additional passengers even if 1 since we receive a separate payment from every passenger.

The expectations are exactly the same for the airplanes, as well, but the aviation industry uses the different engineering branches and disciplines such as aerodynamics, mechanics, electricity, and avionics together. To achieve the said balance, organization of the much more crowded groups and simultaneous and intense operation of the same are required.

There is one goal about the maintenance of airplanes; to render the safe and economical flight of the airplanes continuous.  All the efforts given during the maintenance are given in order to eliminate the possibility of failure of the airplane when least expected and for providing a continuous flight of the same in a problem-free manner. 

Airplanes are subjected to many tough tests when they are still at the design stage. Their durability is tested by being forced under exaggerated conditions which are not presumed to be encountered during the normal flights. In case of any problem, the design is reviewed and necessary reinforcements or changes are made in the relevant points. After passing these tests performed under the control of the relevant civil aviation authorities in safety and becoming entitled to receive the flight certificate, the airplanes can launch commercial flights to provide service for the passengers.

All the data obtained during the design, test and certification processes of an airplane launching its commercial flights are saved. This information is blended with the common saving belonging to the civil aviation and converted into a maintenance program by the locomotives of the industry. In other words, while the airplanes themselves are designed on the one hand, the initial state of the maintenance to be applied to the flight process is designed on the other hand.

Maintenance works were performed by airplane mechanics in 1910s, first years of the aviation and each airline company formed and applied its maintenance program. When it comes to 1930s, a need for centralized management was born due to several reasons. The first step was taken according to the Article 5 of the bulletin published by American Trade Secretariat with the name Aeronautical Bulletin 7-E;

"Operating efficiency as maximum as possible in the maintenance to be applied in all the airplanes also including the motors and equipment thereof will be taken as a basis and within the scope of this aim, fixed maintenance periods for the examination, repair and maintenance to be realized in airplane motor, equipment and devices will be determined by the Trade Secretariat."

Thus, scope of the maintenance determined by each airline previously was first controlled by a centralized authority. When it comes to 1950s, larger airplanes of advanced engineering products of its day such as Boeing 707 and DC-8 came into service. Along with these airplanes, the task of determining the scope of maintenance to be applied was assigned to the airplane manufacturers by being taken from the mechanics and operators due to the expansion of the scope.

Federal Aviation Administration (FAA) and the leaders of the industry applied an approach called Maintenance Steering Group (MSG) and determined the scope of the maintenance for Boeing 747-100 and its motors on 10 June 1968. With Boeing 747-100 performing its first flight with a nickname "Jumbo Jet", an official approach of "designing maintenance" was implemented on 9 February 1969. Although the airplanes today are much more developed, the scope of the maintenance to be applied is built on the philosophy of MSG starting with Boeing 747.

Volume of the study of designing maintenance is quite large and Boeing 777 is a good example to understand this volume. Design study of the maintenance program belonging to Boeing 777 started in 1990 and was completed 1 month before receiving the commercial flight certificate in 1995. It took 5 years for the program to take its final state.

The board performing the said study is called Maintenance Review Board (MRB) and determines the scope of the minimum maintenance required to be made in a certain type of airplane. This board is composed of a total of 80 - 100 participants who are experts in their subjects coming from the centralized aviation authority, airplane/motor/part manufacturers, suppliers, airline companies and additional aviation groups.

Similar to Boeing 777, Maintenance Review Boards dedicated to each of the airplane types such as Airbus A350, Embraer E-190, ATR 72 are formed and the scope of the maintenance required to be made on the airplanes is decided within the philosophy of MSG. MSG study, however, forms the philosophy of maintenance itself. MSG, different from MRB, is the super group which is composed of the most experienced participants in their fields and to which all the MRB rules are subjected. MSG group basically predict which system of the airplanes designed newly may need maintenance in which intervals and in which scope and requires this approach to be applied in each type of airplane.

All the maintenance processes determined in line with the MSG approach by MRB specific to a certain type of airplane are required to be applied by all the airline companies and operators serving with the relevant airplane type anywhere in the world. In case of a need of change, this can be realized with the relevant authority permission.

During the operations of the MRBs, a certain number is designated for each maintenance process to be applied in airplanes as required by MSG. For instance, the task of changing the engine oil we perform frequently in the passenger cars can be regarded as equivalent to labelling thereof as 12-34-56. Unlike the passenger cars, as the airplanes are in international circulation at any time, such labelling becomes necessary in order to achieve a common communication language between different countries, different languages and different cultures. When a certain maintenance process number is pronounced for a certain type of airplane, the same process is understood by everyone regardless of the country.

Numbers of the maintenance required to be applied in an average airplane vary between 1500 and 4000. To properly organize such a broad and extensive maintenance processes, a large number of employees are working in the maintenance hangars and technical maintenance departments of the airlines.

To conclude, scope of maintenance belonging to the airplanes is built on the philosophies formed by crowded groups experts in their subjects based on the experiences collected within the years and is continuously advancing on the road to improvement thanks to the legs provided in Air Transportation Cycle.