In weight and balance terminology, LEMAC and TEMAC are defined in terms of distance from what reference point?

• A. The datum.
• B. The wing leading edge.
• C. The center of gravity.
• D. The engine location.

Answer: (A)

In weight and balance calculations, all distances (arms) are measured from a fixed reference plane called the datum. LEMAC and TEMAC specify the location of the Mean Aerodynamic Chord by giving how far forward or aft its leading edge and trailing edge are from that datum. So these terms are defined as distances from the datum to the leading edge and trailing edge of the MAC, respectively. This makes the MAC location and the related moment arms unambiguous and consistent for calculating the aircraft’s center of gravity.

Other reference points like the wing leading edge or engine location aren’t used as the universal origin for these measurements, and the center of gravity isn’t a reference point for arms—it's the result you determine from those arms and weights.