run up
To warm up and test an airplane before a flight.
run up: engine warm-up and systems check before flight
A run up is the systematic process of starting an aircraft's engines, warming them to operating temperature, and verifying that all systems function correctly before the aircraft is released for flight. It happens on the ground, either at the gate, in a maintenance area, or at a designated run up pad away from taxiways and populated areas. The pilot or maintenance technician advances throttle gradually, monitors engine parameters, and steps through a checklist of tests: alternator output, vacuum or pressure systems, flight control surfaces, hydraulic pressure, fuel system, and electrical systems.
The duration and complexity depend on the aircraft type and whether it is a scheduled pre-flight run up or a troubleshooting check after maintenance. A small single-engine aircraft might require 10 to 15 minutes; a regional jet or larger transport aircraft can take 30 minutes or more. Piston engines need time to reach normal operating temperature before high-power checks; turbine engines stabilize faster but require monitoring of exhaust gas temperature and other specific parameters that vary by engine model.
Run ups reveal problems that static inspection cannot: engine roughness, instrument unreliability, electrical faults under load, and control anomalies. Magnetos on piston engines are tested by deliberately leaning the fuel mixture slightly and observing engine response. Propeller governors are cycled to confirm blade pitch control works. Vacuum systems or pressure pumps are verified to hold specified ranges. Radios, navigation equipment, and autopilot modes are powered and tested to minimums. Brake operation is confirmed on the ground before takeoff is considered safe.
If a run up reveals a discrepancy, the flight does not proceed until the fault is corrected and a follow-up run up confirms the fix. This is why run ups matter: they catch failures while the aircraft is still safely on the ground. A failed alternator, a stuck valve, or a hydraulic leak discovered during run up prevents an in-flight emergency.
The term 'run up' reflects the literal action of running the engines up to higher power settings than idle for the first time that day. It differs from a simple engine start check, which confirms only that the engine will light and idle. A run up is thorough, scheduled, and documented. Pilots and maintenance technicians cross off each item on the run up checklist before signing the aircraft as ready for service.