What is the primary reason why flight is unsafe when the center of gravity is out of limits?

The primary reason why flight is unsafe when the center of gravity (CG) is out of limits revolves around the impact on the aircraft's performance, particularly in terms of stall recovery. When the CG is positioned outside of the prescribed limits, the aircraft may exhibit altered flight characteristics that can negatively affect its stability and control. If the CG is too far forward, it can lead to a nose-heavy configuration, making it more challenging to raise the nose during a stall recovery. Conversely, if the CG is too far aft, the aircraft can become unstable and sensitive to control inputs. In such cases, the pilot may find that they cannot recover from a stall in a timely manner or at all, which poses significant risks to flight safety.

The other options, while they highlight issues that can arise from an out-of-limits CG, do not encapsulate the most critical concern as effectively as the risk of slow or impossible stall recovery. Stalls are critical moments in flight, and having a CG that complicates recovery can lead to accidents, making this aspect paramount for effective flight safety. Ensuring the CG remains within the specified limits is essential to maintain controllability and safety throughout various stages of flight.