Flight Performance, Weight and Balance, and Loading for Helicopters
Performance fundamentals
Helicopter performance depends on density altitude, weight, wind and the power available. Know the hover ceiling in ground effect (HIGE) and out of ground effect (HOGE), and why HOGE is always lower. Understand translational lift, effective translational lift, and how it improves performance in forward flight. Know the avoid curve (height-velocity diagram) and the concept of the dead man's curve: the region where a safe autorotation landing is unlikely.
Weight and balance
Know the terms: empty weight, basic empty weight, maximum gross weight, useful load, centre of gravity (CG) and the datum. For helicopters, the lateral CG matters as much as the longitudinal CG, and many types have a narrow lateral envelope. Loading errors shift the CG and can make the aircraft uncontrollable in hover. Compute weight and moment, then divide total moment by total weight to find the CG position.
Traps in questions
Questions often give you a load to add and ask whether the flight is legal: check both maximum weight and CG limits, not just weight. Watch for fuel density changes: litres must be converted to kilograms using the correct density. Another trap is assuming HIGE figures apply to a confined area with obstacles; use HOGE.
Worked example
Given an empty weight of 700 kg at 2.5 m from datum and a pilot of 80 kg at 1.5 m, the total moment is 700×2.5 + 80×1.5 = 1750 + 120 = 1870 kg·m, and the CG is 1870 / 780 ≈ 2.40 m. Compare that value with the envelope before dispatch.