The ABC’S of Jet Engine Maintenance
Maintaining an aircraft is far more than washing the exterior and cleaning up the interior of the cabin. The maintenance cycle can be defined by various levels, each named with an alphabetical letter in progressing levels of complexity. Check A is the most routine, taking no more than an hour or two. Check C on the other hand, is a far more extensive checking of independent aircraft components, functions, tooling, and equipment.
Before flight, the pilot or mechanic is required to visually check the aircraft components and instruments. Access panels should be inspected for any obvious signs of damage. Oxygen systems and emergency lighting must also be checked to ensure they are functioning properly. Inside the cockpit, the pilot should verify that the brake accumulator pressure is correct. To help understand the various check stages, this blog will track one particular aircraft component throughout the check stages. The reciprocating engine is the main component of a jet therefore requires adherence to correct safety regulations. During Check A, the pilot cannot fully inspect the aircraft engine, but can check for any instrument irregularities.
Both Check A and Check B are known as lighter checks and can be performed at Fixed Base Operators such as the airport. Check B may require special equipment or tests to determine the status of a system of component. Disassembly is not necessary during this check. Engine diagnostic equipment is an example of a specialized kit that may be used during check B.
Heavier checks are contracted out to Maintenance Repair and Overhauls facilities (MRO)s. The aircraft is disassembled and categorized into parts. Each component is checked for any physical irregularities such as cracks, corrosive damage, heat damage, or dents. If a part has any of these, it is replaced. Specialized equipment and checks are needed to successfully carry out this stage of testing. Hardware such as seals, aircraft stabilizers, and bolts also need to be tested and verified.
The FAA has the final say in terms of the safety of the aircraft. Title 14, Section 19, of the FAA Code of Federal Regulations states that no person can operate an aircraft unless it had both an annual inspection and an inspection for the issuance of an airworthiness certificate. Each person carrying out the 100-hour inspection is required to fill out a checklist that includes the scope of work and details of the item they are checking. Further regulations for aircraft maintenance, specifically turbine-engine-powered aircraft, are set forth in Part 43 of the CFR. After the 100-hour inspection is complete, but before the aircraft is returned to service, the turbine engine must be run to determine satisfactory performance in accordance with the manufacturer’s recommendations.
Finally, everything and anything to do with the maintenance of the aircraft must be documented. If a part is classified as ‘life limited’ by design, the part must be replaced within a specific timeframe. The life status of a part is the accumulated cycles, hours, or replacement limit of a part. With both of these classifications, a mechanic can identify which parts will need a replacement, regardless of their physical condition. The maintenance of a jet engine is highly regulated process that cross references the physical condition of the aircraft on a daily, monthly, and yearly basis with the written documentation of the previous conditions and of the aircraft. The FAA will only deem the aircraft airworthy when every one of the regulations are met.
Posted on July 9, 2019