A heavy maintenance check is a planned, extensive aircraft maintenance event that involves major inspection, access, repair, modification, and documentation activities. In aerospace MRO, it commonly refers to a base maintenance visit where large portions of the aircraft may be opened, inspected, tested, repaired, or restored under controlled work instructions and quality procedures.
Heavy maintenance checks are commonly managed through work packages, task cards, inspection findings, nonconformance records, part traceability, approvals, and maintenance records. The exact scope depends on the aircraft type, maintenance program, operator requirements, repair station procedures, and applicable regulatory expectations.
The term should not be confused with routine line maintenance or a single inspection task. A heavy check is usually broader, more invasive, and more documentation-intensive. In commercial aviation, related terms such as C-check, D-check, heavy check, and heavy maintenance visit may be used, but their precise meaning can vary by operator, aircraft program, and maintenance schedule.