Differences in the Aircraft Inspection Program

How they categorize aircraft maintenance inspection?

Aircraft maintenance inspection program can be classified into scheduled maintenance and unscheduled maintenance. Since not all materials and component wear or become fatigued at the same rate, the scheduled maintenance is planned by referring to certain units of maintenance intervals such as chronological units, and cycle-driven units. The chronological units of measurement are for component or material that is dependent on the number of flight hours (FH) and calendar time (Cal). Example of component that is under chronological inspection is Electric Generator which inspects for maintenance depending on FH. Meanwhile, cycle-driven inspection is for component or material that is dependent on the number of flight cycles (FC). Example of component that is required to inspect per cycle-driven inspection is Landing Gear ("Aircraft Maintenance - SKYbrary Aviation Safety", n.d.).

Using both of these maintenance interval units, the maintenance engineering department of each airline will schedule their fleets for maintenance. Example of a scheduled maintenance inspection is ABC check system.

Next, the unscheduled maintenance inspection is done only when a system or component malfunctioned or suspected for malfunctioning. This inspection cannot prognosticate. The Federal Aviation Administration (FAA) requires that all the determination for maintenance inspection need to be made before the maintenance personnel working on the aircraft. The determination methods and procedures for unscheduled maintenance should be in the manual of the aircraft manufacturer ("The Different Types of Aircraft Maintenance Inspections - Aircraft Compare", n.d.). Example of unscheduled maintenance task is the replacement of Main Landing Gear (MLG) brake assembly due to wear.

Is there any difference between commercial, business and general aviation in aircraft maintenance and inspection programs?

Due to the differences in the operation of commercial, business and general aviation aircraft, the scheduled maintenance and inspection programs are varied to each other. The commercial aircraft has the highest number of maintenance and inspection compared to all different types. Commercial aircraft travel all around the world and operate at the highest frequency. Therefore, the aircraft is required to undergone multilayer of inspection as per the FAR 121 maintenance regulations which known as preflight checks, hourly inspection, annual inspection and progressive inspection. 

Meanwhile, business type aircraft which are chartered or private jets have much lower maintenance requirements than the commercial type. Mainly because business aircraft operate less frequently. The hourly inspection will be at a lower rate on business aircraft. However, preflight checks and annual inspections will remain as per the requirement in FAR 135 maintenance regulations. Last but not least, the General Aviation (GA) have similar but special requirements than business aircraft. The GA aircraft have similar annual and 100-hour inspection. The FAA stated in FAR 91.409 that the airline operator or owner of GA must maintain the airworthiness of the aircraft and engine during the time between inspection by having any defects corrected and documented ("The Basics of Maintenance in General Aviation", n.d.). The FAA also added that preventive maintenance would be required on every 25 flight hours (FH) and minor maintenance on every 100 FH.

Both the FAR 121 and FAR 135 carriers are required to use a maintenance program for its aircraft where FAR 91 operators are only required to implement an inspection program. The FAR 121 and FAR 135 are also responsible for the development and use of a maintenance program and manual which is unique to each air carrier, determining the methods of performing maintenance, and mandating a required inspection list. The FAR 91 operator is only able to select an existing inspection program and to schedule their fleet for inspections, and to ensure that items found during the inspection are repaired prior to the next inspection ("Aircraft inspections – the requirements to keep them flying", 2018).

 Why documentation is important in aircraft maintenance?

The documentation of every maintenance inspection is crucial for the purpose of references. For Commercial aviation, the 14 CFR 121.380 requires the air operator to retain the maintenance record for the periods specified in paragraph C of the regulation ("14 CFR § 121.380 - Maintenance recording requirements.", n.d.). Secondly, the operator also need not record the total time in service of an engine or propeller on a transport category cargo aircraft, a transport category aircraft that has a passenger seat configuration of more than 30 seats, or a non-transport category aircraft type certificated before January 1, 1958, until March 20, 1997, or the date of the first overhaul of the engine or propeller. Besides that, the operator also shall make sure that all the maintenance records required to be kept properly or readily available for inspection by the Administrator or any authorized representative of the National Transportation Safety Board (NTSB).

Meanwhile, for GA aircraft, the 14 CFR 91.1439 requires program manager who maintains aircraft under the Continuous Airworthiness Maintenance Program (CAMP) to retain the records for the period specified in paragraph B of the regulation ("14 CFR § 91.1439 - CAMP: Maintenance recording requirements.", n.d.). The program manager also needs to keep the record by this section except for the records of the last complete overhaul until the work is repeated or superseded by other work or for one year after the work is done. The record of this section also must be retained unless transferred with the aircraft at the time the aircraft is sold. Next, the program manager shall make sure that all the maintenance records required to be adequately kept and readily available for inspection by the Administrator or any authorized representative of the National Transportation Safety Board (NTSB).

References

14 CFR § 91.1439 - CAMP: Maintenance recording requirements. Retrieved 16 April 2020, from https://www.law.cornell.edu/cfr/text/14/91.1439

14 CFR § 121.380 - Maintenance recording requirements. Retrieved 16 April 2020, from https://www.law.cornell.edu/cfr/text/14/121.380

Aircraft inspections – the requirements to keep them flying. (2018). Retrieved 16 April 2020, from https://www.mototok.com/blog/aircraft-inspections-the-requirements

Aircraft Maintenance - SKYbrary Aviation Safety. Retrieved 16 April 2020, from https://www.skybrary.aero/index.php/Aircraft_Maintenance

The Basics of Maintenance in General Aviation. Retrieved 16 April 2020, from https://www.lycoming.com/content/basics-maintenance-general-aviation

The Different Types of Aircraft Maintenance Inspections - Aircraft Compare. Retrieved 16 April 2020, from https://www.aircraftcompare.com/blog/types-of-aircraft-inspections/