Which maximum range factor decreases as weight decreases?

The correct answer is airspeed because as the weight of the aircraft decreases, the optimal airspeed for achieving maximum range also decreases. In lighter-than-air flight, maximum range typically occurs at a specific cruise speed that minimizes drag and maximizes lift-to-drag ratio. When the weight of the balloon or airship is reduced, it can achieve efficient flight at a lower airspeed, thus contributing to an improved range because it reduces induced drag and optimizes fuel efficiency.

A lower weight means the vehicle requires less lift to maintain altitude, allowing for a more favorable flight profile. As speed decreases for a given weight, the aerodynamic efficiency can increase, further enhancing the range potential. This relationship is vital for pilots and operators to understand for effective flight planning and operational strategies in lighter-than-air craft.

The other factors—altitude, angle of attack, and engine performance—do not directly decrease related to a decrease in weight in the same context of maximum range. Instead, they may be influenced by other parameters or operational considerations but are not inherently tied to a simple weight decrease as seen with airspeed.