What must the TO DATASET MENU be set to when the OAT is from 5 to 10C?

When the Outside Air Temperature (OAT) is between 5 to 10 degrees Celsius, the TO DATASET MENU should be set to "ENG." This setting is crucial because it modifies the takeoff performance calculations to ensure they accommodate the specific environmental conditions, particularly in colder weather scenarios.

The "ENG" setting is designed to reference engine performance data relevant for takeoff, which is essential for determining the necessary thrust settings and ensuring that the aircraft can achieve the required performance during the takeoff phase. Ensuring that the correct dataset is selected in correlation with the OAT allows pilots to optimize aircraft performance, enhance safety, and maintain compliance with operational regulations.

While the other options—such as ALL, TO, and GA—may pertain to different operational contexts or performance datasets, they do not specifically address the need for engine-related data in the given temperature range. Therefore, selecting "ENG" is the most effective way to ensure accurate performance data for takeoff in these conditions.