Final answer:
Aircraft are jacked indoors for weighing to prevent air currents from affecting scale readings, providing a level position for accurate weighing. While simulating weightlessness, an aircraft achieves this temporarily without the continuous nature of orbital free-fall.
Step-by-step explanation:
It is generally necessary to jack an aircraft indoors for weighing to ensure that air currents do not destabilize the scales. When weighing an aircraft, precise measurements are critical, and outdoor elements such as wind can affect the stability and accuracy of the scale readings. Indoor environments offer controlled conditions where wind cannot perturb the equilibrium of the scales, allowing for more accurate weight assessments. Additionally, having the aircraft indoors ensures that it can be positioned levelly, a crucial factor for proper weight distribution measurements.
Simulated weightlessness in an accelerating aircraft and in orbit both result from experiencing free fall. When astronauts are in a cargo aircraft accelerating downward at the acceleration due to gravity (g), they will appear to be weightless on a scale just like in orbital free fall. However, this weightlessness differs from being in space orbit because in an orbiting spacecraft, there is continuous free-fall around the Earth without the presence of air resistance, while the aircraft has to deal with air resistance and can only mimic this effect temporarily during parabolic flight maneuvers.