Which combination correctly lists all five factors that affect helicopter lift capacity (W.H.A.T.F)?

Which combination correctly lists all five factors that affect helicopter lift capacity (W.H.A.T.F)?

• A. Wind; Humidity; Altitude; Temperature; Fuel
• B. Wind; Heat; Altitude; Temperature; Fuel
• C. Wind; Humidity; Altitude; Temperature
• D. Wind; Humidity; Humidity; Temperature; Fuel

Answer: (A)

Lift capacity depends on two forces: the air the rotor can push against (which determines lift) and the weight the rotor must hold. The factors that change air density are wind, humidity, altitude, and temperature, while fuel changes the weight. So the five factors that affect helicopter lift capacity are wind, humidity, altitude, temperature, and fuel. Humidity lowers air density a bit, altitude and temperature lower density more, wind can alter rotor efficiency and the amount of lift needed for a hover or climb, and fuel adds weight that reduces the lift margin available. The other options omit one of these density effects or replace humidity with heat, so they don’t capture all five factors.

Lift capacity depends on two forces: the air the rotor can push against (which determines lift) and the weight the rotor must hold. The factors that change air density are wind, humidity, altitude, and temperature, while fuel changes the weight. So the five factors that affect helicopter lift capacity are wind, humidity, altitude, temperature, and fuel. Humidity lowers air density a bit, altitude and temperature lower density more, wind can alter rotor efficiency and the amount of lift needed for a hover or climb, and fuel adds weight that reduces the lift margin available. The other options omit one of these density effects or replace humidity with heat, so they don’t capture all five factors.