What is the approximate time required to complete an airstart sequence at 125 KIAS?

The approximate time required to complete an airstart sequence at 125 KIAS (Knots Indicated Airspeed) is around 40 seconds. This timeframe includes all the critical steps needed to successfully restart the engine following an in-flight shutdown.

During an airstart, the pilot must manage a series of tasks effectively, such as establishing the correct airspeed, configuring the aircraft systems, selecting the appropriate fuel and ignition settings, and monitoring the engine parameters to ensure a successful restart. The recommended procedures are designed to maximize the chances of a successful airstart while maintaining sufficient altitude and airspeed.

When considering the other timeframes suggested, 20 seconds would be too quick to accomplish all necessary checks and actions, leading to a higher risk of failure. Likewise, 30 seconds doesn't allow enough time for thorough task performance, while both 50 seconds and beyond would extend the sequence unnecessarily, potentially impacting altitude and performance if the aircraft were losing energy during the maneuver.

Thus, the choice of 40 seconds strikes a balance between safety and efficiency, making it the appropriate answer for the duration of an airstart sequence at 125 KIAS.