What document describes the proper use of cowl flaps on an air-cooled engine?

• A. The pilot's operating handbook.
• B. The service bulletin.
• C. The maintenance manual.
• D. The airworthiness directive.

Answer: (A)

The pilot's operating handbook is the reference for how to operate the aircraft in flight, including engine cooling controls like cowl flaps. It provides normal operating procedures and guidelines to keep engine temperatures within limits across different power settings and conditions. That’s where you’ll find the recommended use of cowl flaps during warmup, takeoff, climb, cruise, and descent. The other documents serve different roles: service bulletins address modifications or repairs, maintenance manuals cover inspections and servicing tasks, and airworthiness directives impose mandatory regulatory actions. So for how to properly use cowl flaps, the pilot's operating handbook is the go-to source.