What is the minimum Ng for a successful engine start?

The minimum Ng (gas generator speed) for a successful engine start is crucial as it ensures that the engine has reached a sufficient rotational speed to sustain compression and initiate combustion effectively. Achieving at least 13% Ng indicates that the starter has engaged properly and that the engine is on its way to developing the necessary parameters for engine operation.

Being above this threshold allows the fuel to ignite and the engine to maintain a stable start sequence. If the Ng is below this level, it may result in a failed start since there may not be enough airflow for combustion or the engine may not develop the power needed to continue running. This critical speed serves as a baseline for safe engine ignition and subsequent acceleration to operational performance, making the 13% Ng the correct choice for a successful start.