A Method to Compare Turbine Engine Airstart Times

Turbine engine airstarts are conducted throughout the aircraft airspeed/altitude envelope in ground-based simulation test facilities and in flight tests to ensure safe and reliable engine operation. Differences in airstart times are attributable to variations in engine turnaround speed (the engine core speed at which the airstart is initiated in spooldown airstarts); combustor lightoff time; installation effects such as customer bleed and power extraction; starter motor torque; fuel flow scheduling; and engine-to-engine variation and degradation. An analytical approach is presented to account for these differences and adjust engine airstart time for a low-bypass, twin-spool, military, turbofan engine. Two examples are presented illustrating the difference in airstart times and the analytical approach used to adjust the start times.