The all-up mass (AUM) of a helicopter refers to its total weight, including fuel, passengers, cargo, and the helicopter itself. The AUM directly affects the helicopter’s maneuvering ability because a heavier helicopter requires more lift and power to control, particularly during sharp turns, rapid acceleration, or deceleration.

When a helicopter is heavier, its inertia (resistance to changes in motion) increases. At higher speeds, this means that the helicopter will have more momentum. To slow down or stop this momentum, the rotor system needs to generate more lift and drag, which requires additional power from the engine.

• More Power to Stop: A heavier helicopter moving at high speed has more kinetic energy. To decelerate, the rotor blades must provide additional force (in the form of lift and drag) to counteract this energy. This requires more engine power because the rotor needs to work harder to slow down the heavy helicopter.
• Reduced Maneuverability: With a higher AUM, the helicopter becomes less agile. Rapid changes in direction, such as quick stops or tight turns, require more effort from both the pilot and the helicopter's systems, limiting how quickly the helicopter can respond. This is because the extra weight increases the demands on the rotor system and engine to maintain control during maneuvers.

In summary, the heavier the helicopter (higher AUM), the more power is required to perform quick maneuvers, especially when stopping or slowing down at high speeds, as the aircraft's increased inertia makes it harder to control.