Subscriber question:
"I am a student pilot using rental Cessna 172s with many hours on the airframes. One has almost 22,000. The planes are well maintained, but when does long-term metal fatigue factor in? Or do the 100-hour inspections and annuals look for this?" — Randy B.
Bob:
“Aging aircraft issues are relevant across our entire aviation fleet, not just in the Cessna family. Your questions are valid and are constantly being reviewed by both industry and FAA engineers.
When the holder of an Inspection Authorization or an Authorized Repair Station signs off an aircraft as airworthy it means that: the condition of an aircraft, airframe, engine, propeller, appliance, or component part where it conforms to its approved type design, is in a condition for safe operation. Remember, it’s a two-prong definition: conformity with type design and in condition for safe operation.
During the annual inspection (or 100-hour inspection), each aircraft must conform to the type certificate under which it was built. A type certificate is the way we approve the design of a specific aircraft, aircraft engine, aircraft propeller, or other major aviation-related product. A type certificate authorizes a manufacturer to make the product in the specific way covered by the certificate.
Conformity is determined by the annual. Safe condition for safe operation is determined by correction of any items found not to conform during the inspection.
Additionally, the Cessna 172 is non-pressurized and therefore isn’t subject to the stress of a pressurized airframe. Corrosion is inspected at least annually or sooner in the case of an aircraft that’s held out for hire.
By flying with a reputable company who maintains their aircraft according to published guidance and doing due diligence on your preflight, you can feel confident that you are flying a safe aircraft.”
Do you think total airframe hours is a growing safety concern?
