If all index units are positive, where would the location of the datum be when computing weight and balance?

When computing weight and balance in aviation, the datum is an essential reference point. It is a specific point from which all horizontal measurements are taken. If all index units are positive, it indicates that all moment arms measured are extending forward from the datum. In this scenario, the datum is established in a position that allows for a clear and manageable calculation of moments towards the center of gravity.

In the context of the question, when the index units are all positive, the logical placement of the datum would be at the nose or out in front of the airplane. This configuration allows for effective measurement and calculation of the weight distribution throughout the aircraft.

Placing the datum at the tail or center of gravity would result in moments that are either confusing or negative, making it challenging to maintain an accurate calculation of the aircraft's balance and stability. Thus, the location of the datum is critical and must be based not only on the general structure of the aircraft but also on the values derived from the weight and balance computations.