The C-checks are one of the heavy maintenance shop visits that aircraft go through multiple times during their operational lifespan. About every two to three years, 10,000 flight hours, or 5,000 flight cycles, a narrowbody jet is taken out of service for a C-check. A widebody aircraft can have a C-check performed every 8,000 flight hours or 3,000 flight cycles.
Labor hours and teams
The first C-check for an aircraft at a maintenance shop takes about 1,000-2,000 labor hours. Depending on the scope and complexity of the maintenance plan, some C-checks can take as many as 6,000 labor hours. With the aircraft out of service for up to four weeks, the operator may expect to spend several million dollars for a C-check.
For any C-check, maintenance teams are formed for each section, which typically comprise Aircraft Maintenance Mechanics (AMM), Aircraft Maintenance Engineers (AME), Quality Inspectors, and Project Managers.
The first C-check
The airframe is relatively newer during the first visit to the maintenance shop. That means there is minimum or no stress damage to the structure. Similarly, minor or no corrosion, heavy wear, or metal fatigue is typically observed. A team of several people inspects pumps, actuators, and other complex assemblies and repairs where necessary.
A different team of AMMs and AMEs detach power plants from pylons for a detailed inspection and repairs. All sections, from engine cowlings to thrust reversers and the exhaust system, are inspected and repaired for safe operations.
It is noteworthy that at about 5,000 flight cycles, the engines may not require a complete overhaul. A comprehensive inspection with a minimum maintenance work scope may only be needed at this point.
The entire passenger cabin is dismantled – seats, overhead bins, doors, galleys, and lavatories all come off. The floor carpeting may also be stripped for refurbishing. Cabin insulation, emergency equipment, and electrical wires are extensively inspected for wear and damage.
While the cabin infrastructure gets overhauled off-site, the cabin team inspects and repairs insulation, emergency equipment, and miles of electrical wires.
Subsequent C-checks
With the aircraft having been through many more flight cycles, subsequent C-checks can be much more extensive. During subsequent visits, the Airworthiness Directives (ADs) and Service Bulletins (SBs) also kick in.
To maintain a necessary safety standard, commercial aircraft operators must comply with all ADs and SBs within the acceptable timeline provided by the local regulatory authority.
Extensive C-checks also include a comprehensive inspection of the load-bearing components of the aircraft. The fuselage structure, wings, and engine pylons are examined for wear and stress. With many pressurization cycles under the belt, structural elements are more prone to metal fatigue.
Control surfaces are examined for standard functionality under various conditions. Necessary repairs are made to all control surfaces.
With multiple teams working on different aircraft exterior and interior sections, a C-check can last between two and four weeks. Assuming an average of 5,000 labor hours for an extensive C-check and a duration of three weeks, a workforce of nearly 40 full-time individuals is required.
Source: simpleflying.com