Airworthiness, Maintenance and Continuing Airworthiness (Parts 21, 39, 43, 45, 47, 91 Subpart E)
The chain
- Part 21 - design and certification: type certificates, supplemental type certificates, approved parts, modifications and export certificates of airworthiness.
- Part 39 - airworthiness directives. Compliance is mandatory and is a condition of the certificate of airworthiness remaining valid.
- Part 43 - who may perform maintenance, and how it is released.
- Part 45 - continuing airworthiness management: the maintenance programme, defect control, directive records, mass and balance.
- Part 47 - registration and nationality marks.
- Part 91 Subpart E - maintenance rules for aircraft operating under Part 91, including the maintenance release, inspection intervals, MEL use, pilot-performed maintenance and defect reporting.
A certificate of airworthiness does not "expire" in the ordinary sense; it ceases to be valid when maintenance, directives, modifications or mass and balance fall out of compliance.
Worked example
A 100-hour inspection falls due at 1,450 airframe hours. The aircraft is at 1,442 hours and a 12-hour flight is planned. Only 8 hours remain before the limit. The flight must be trimmed to 8 hours, or the inspection brought forward, or a specific ferry or special flight approval obtained. Dispatch for the extra 4 hours makes the maintenance release invalid.
Traps
- Confusing a maintenance release with an annual or periodic inspection - they are different items.
- Assuming airworthiness directives can be deferred like a minor defect.
- Believing an unapproved modification is acceptable because a mechanic signed it out.
- Forgetting defect reporting and record retention duties.