When should engine run up be performed?

• A. Only after clearance for takeoff
• B. Before taxi
• C. During landing
• D. Any time

Answer: (A)

Engine run-up is a controlled high-power check of the engines to verify proper operation, including ignition/ magnetos, RPM limits, and engine gauges, in a safe, designated area before takeoff. It should be done once you have clearance for takeoff so you’re in the proper phase of flight and ATC is aware you may be applying power near the runway. This timing keeps the operation out of taxiing or runway traffic and allows you to complete the checks with the runway ready to use if everything checks out.

Doing it before taxi, during landing, or at any time would create safety and flow issues: before taxi you might be in a position not designated for high-power testing; during landing you’d be in a critical phase where any abnormal reading could be dangerous; and any time would risk interfering with other traffic and airfield operations. Waiting for takeoff clearance aligns the run-up with the departure sequence and ensures you’re testing in a controlled, appropriate spot.