What condition is required for the activation of the autofeather system?

The activation of the autofeather system is contingent upon both power levers being positioned above approximately 90% N1. This condition is critical because the system is designed to enhance engine performance and safety during flight by automatically feathering the propeller of any engine that is underperforming, particularly in the event of an engine failure.

When both power levers are set above the specified N1 threshold, the system can confirm that the engines are delivering sufficient thrust and can monitor their individual performance effectively. This ensures that the autofeather system engages appropriately should one of the engines begin to fail, allowing the remaining engine(s) to maintain optimal performance and control during flight.

The other conditions listed would either not engage the system or apply scenarios outside the operational parameters intended for the autofeather system, which is primarily aimed at maintaining thrust and control in a multi-engine aircraft configuration during critical phases of flight.