What happens when a multi-engine fixed-wing aircraft does not meet the required climb gradient at KPSO?

When a multi-engine fixed-wing aircraft does not meet the required climb gradient at a specific airport, such as KPSO, the appropriate action is that departure under IFR (Instrument Flight Rules) is not authorized. This situation arises because the climb gradient is critical for ensuring that the aircraft can safely clear obstacles in its flight path immediately after takeoff. A failure to meet this requirement indicates that if the aircraft were to proceed under IFR, it might not have sufficient altitude and maneuver margins to safely navigate the surrounding environment.

In this context, it is essential to adhere to safety regulations that dictate operational parameters. When the required climb gradient is not achievable, it significantly limits the options available for takeoff under IFR rules, as IFR procedures typically assume compliance with established climb capability. Therefore, taking off without the necessary climb gradient could present serious risks, leading to the prohibition of IFR departures in such scenarios.

The other choices would suggest alternative takeoff operations that may not align with established aviation safety protocols if sufficient climb performance is not demonstrated.