Which of the following factors could affect the lift of a UAS?

The lift of a UAS (Unmanned Aircraft System) is primarily influenced by the physical properties of the air surrounding it, notably temperature and pressure. As temperature increases, air density decreases, which means there are fewer air molecules for the rotors to push down for generating lift. Conversely, at lower temperatures, the denser air provides more lift. Pressure also plays a critical role; at higher altitudes, air pressure is lower, resulting in thinner air and thus reduced lift capacity. This relationship is fundamental to flight dynamics and is crucial for operators to consider when planning flights under various environmental conditions.

Battery charge is important for the overall operation of the UAS, including maintaining power for motor performance, but it does not directly affect the aerodynamic properties influencing lift. GPS signal strength, while vital for navigation and maintaining flight stability, does not impact the physical lift generated by the rotors. Time of day may indirectly affect visibility or other operational aspects, but it does not have a direct impact on the generation of lift itself. Therefore, temperature and pressure are the key factors that directly influence the lift of a UAS.