At what altitude do you require at least 135 KIAS for an airstart maneuver?

For an airstart maneuver, requiring at least 135 KIAS (Knots Indicated Airspeed) is essential to ensure that the aircraft maintains adequate control and aerodynamic efficiency during the maneuver. At 15,000 feet MSL (Mean Sea Level), the air density is significantly lower than at sea level, which directly affects the aircraft's performance.

Operating at this altitude, 135 KIAS helps maintain sufficient airflow over the control surfaces, critical for successful engine restart and overall aircraft control in the event of an engine failure. This speed also provides the necessary margin relative to stall speed, allowing the pilot to react effectively to any unexpected circumstances during the airstart procedure.

In contrast, at altitudes below this, lower airspeeds may still be effective for airstarts, but as altitude increases and air density continues to decrease, a higher airspeed threshold becomes vital to compensate for the diminished performance capability of the aircraft. Thus, the requirements for airstart maneuvers become more stringent with altitude growth, confirming that 15,000 feet is the appropriate threshold for maintaining safe airstart speeds.