On-condition maintenance relies on operating parameters specified by whom?

• A. The airframe owner
• B. The operator
• C. The engine manufacturer
• D. The regulatory authority

Answer: (C)

On-condition maintenance relies on operating parameters defined by the engine manufacturer. The manufacturer tests and documents the normal ranges and wear indicators for the engine, such as oil pressure and temperature, exhaust gas temperature, engine speed, and vibration levels. These manufacturer-specified limits tell you when performance is out of spec and maintenance or inspection is needed. The operator monitors against these limits and uses them to trigger service, while the regulatory authority sets general rules. However, the specific engine-trigger limits come from the engine maker, not from the airframe owner or operator alone.