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

When all index units are positive in weight and balance calculations, it indicates that the reference point, or datum, is located at the nose of the aircraft, or even further out in front. This setup means that all measurements for various components' distances to the datum will yield positive values, as they are measured forward from that point.

Placing the datum at the nose is common in many aircraft designs, particularly smaller general aviation aircraft, as it allows for a straightforward way to assess the balance of loads and passengers in the cabin and rear storage areas. The distances to components like the fuselage and cargo area will then naturally remain positive, simplifying calculations and maintaining the clarity of measurement when determining the center of gravity and overall stability of the aircraft.

In contrast, locations such as the center of the aircraft or the tail would usually involve a mix of positive and negative values when measurements are taken from those points to various components, which can complicate balance calculations. Similarly, the leading edge of the wings could result in variations in index units depending on the aircraft configuration, making it less common as a datum point for balance purposes. Thus, the correct answer is clearly justified by the expectation of having all positive index values when the datum is positioned at the nose of the aircraft