An airplane has a maximum takeoff weight (MTOW) of 400,000 lb, an operating empty weight (OEW) of 200,000 lb, and a maximum zero fuel weight (MZFW) of 260,000 lb. The maximum usable fuel capacity is 160,000 lb. At maximum structural payload, how much fuel can be loaded before reaching MTOW, and what does this represent?
- A160,000 lb of fuel; this is below the tank capacity, meaning payload can be increased further
- B200,000 lb of fuel; this exceeds tank capacity and is not achievable
- C140,000 lb of fuel; this is the maximum-payload/maximum-range point before further range requires trading payload for fuel
- D60,000 lb of fuel; this represents the aircraft's maximum range condition
Show answer & explanationAnswer & explanation
Correct answer: C. 140,000 lb of fuel; this is the maximum-payload/maximum-range point before further range requires trading payload for fuel
Maximum payload = MZFW - OEW = 260,000 - 200,000 = 60,000 lb. At this payload, the zero fuel weight is 260,000 lb, so fuel that can be added before reaching MTOW = 400,000 - 260,000 = 140,000 lb, which is within the 160,000 lb tank capacity. This is the maximum payload point on the payload/range diagram; beyond this range, additional fuel requires reducing payload to stay within MTOW.
Why the other options are wrong
- A. 160,000 lb of fuel would exceed the 140,000 lb allowed before hitting MTOW at max payload.
- B. 200,000 lb of fuel is not possible since tank capacity is only 160,000 lb and it would exceed MTOW anyway.
- D. 60,000 lb is the maximum payload value, not the fuel load, and does not represent maximum range.
Payload/Range Tradeoff
At maximum structural payload, only limited fuel can be added before MTOW is reached; beyond that range, additional fuel must be offset by reduced payload since total weight is capped at MTOW.
- Max payload = MZFW - OEW
- Fuel available at max payload = MTOW - MZFW
- Beyond this range point, fuel added trades directly against payload
Memory trick: 'Fill the cabin first, then trade seats for fuel'