What is required for conventional or tailwheel aircraft before weighing?

For conventional or tailwheel aircraft, raising the tail to a level flight condition is essential before weighing because it ensures that the aircraft is in a neutral position, reflective of its flight attitude. This positioning allows for an accurate representation of the aircraft's weight and center of gravity, which is crucial for performance calculations and safety assessments.

When the tail is raised, the aircraft simulates the way it would be during flight, enabling the weight distribution to be assessed correctly. This alignment helps to avoid any miscalculations that might arise from weighing the aircraft in an unstable or unrealistic position.

The other options focus on different aspects of aircraft positioning, which do not specifically facilitate an accurate weighing process. For instance, having the nose in a downward position or the wings level with the ground could create a skewed weight distribution and affect the center of gravity measurement. Additionally, equal weight distribution is always a desired state for safety and handling but does not address the specific requirements for preparing a tailwheel aircraft for weighing.