What temperature must the MCDU DATASET MENU be set to ALL?

The correct choice indicates that the MCDU DATASET MENU must be set to ALL when the Static Air Temperature (SAT) is 10°C or below. This procedure is essential for ensuring accurate performance calculations, particularly in colder conditions, where aircraft performance can be affected by the temperature.

When the SAT is at or below 10°C, the aircraft experiences denser air, which can influence lift, drag, engine performance, and takeoff and landing distances. Setting the MCDU DATASET MENU to ALL allows the systems to utilize all available data for making precise calculations, which is vital for safe and efficient flight operations under these specific temperature conditions.

In warmer temperatures, where SAT is above 10°C, the performance parameters account for different environmental influences, and not necessarily all data needs to be included in the calculations. This distinction aims to streamline the performance data used, allowing pilots to focus on the most relevant information based on current conditions.