What is the minimum altitude at which an airstart procedure is not recommended?

The minimum altitude at which an airstart procedure is not recommended is 2000 feet above ground level (AGL). This altitude is considered critical because below this level, the aircraft may not have sufficient altitude to recover from a failed airstart attempt or to safely maneuver if the engine does not restart.

At altitudes lower than this, pilots have reduced time and altitude to react to any issues, increasing the risk of an unsuccessful airstart leading to a loss of control and potentially an emergency landing or worse. Maintaining a safety buffer helps ensure that there is enough vertical space to execute necessary maneuvers or to carry out an emergency descent if the situation calls for it.

Therefore, 2000 feet AGL is considered a safer minimum altitude for attempting an airstart, providing adequate reaction time and options for the pilot in case of failure.