Load Planning for a Supply Drop Run
A transport aircraft is tasked to carry relief supplies on a short sector. The aircraft has a maximum take-off mass of 22,000 kg and a maximum landing mass of 20,000 kg. Its basic operating mass (empty plus crew and fixed equipment) is 14,500 kg. Fuel burn for the sector is estimated at 1,800 kg, and the crew plans to land with a 600 kg fuel reserve. Cargo is packed in crates of 250 kg each. The loadmaster has 30 crates ready and wants to take as many as possible.
1. Calculate the maximum number of crates that can be carried while respecting both the take-off and landing mass limits.
Read the worked answer
Work backwards from the landing limit first, since landing mass includes reserve fuel.
Landing mass limit: 20,000 kg. Landing mass = basic operating mass + cargo + reserve fuel. Cargo allowed = 20,000 − 14,500 − 600 = 4,900 kg.
Take-off mass limit: 22,000 kg. Take-off mass = basic operating mass + cargo + total fuel (burn + reserve = 1,800 + 600 = 2,400 kg). Cargo allowed = 22,000 − 14,500 − 2,400 = 5,100 kg.
The binding limit is the smaller, 4,900 kg. Number of crates = 4,900 / 250 = 19.6, so 19 crates (4,750 kg). Twenty crates would be 5,000 kg, exceeding the landing limit by 100 kg.
2. The loadmaster proposes reducing fuel by 200 kg to fit one more crate. Assess whether this is safe and legal.
Read the worked answer
Check the numbers. With 20 crates (5,000 kg) and fuel reduced by 200 kg (burn 1,600 kg, reserve 600 kg, total 2,200 kg):
- Take-off mass = 14,500 + 5,000 + 2,200 = 21,700 kg - within 22,000 kg.
- Landing mass = 14,500 + 5,000 + 600 = 20,100 kg - exceeds the 20,000 kg landing limit by 100 kg.
So the proposal does not work: the landing limit is still breached because the reserve fuel is fixed. Reducing fuel below the reserve is not permissible anyway. The 19-crate load stands unless the reserve or basic mass changes.
3. State the margin situation at 19 crates and explain why the landing limit, not the take-off limit, governed here.
Read the worked answer
At 19 crates (4,750 kg):
- Take-off mass = 14,500 + 4,750 + 2,400 = 21,650 kg (350 kg margin).
- Landing mass = 14,500 + 4,750 + 600 = 19,850 kg (150 kg margin).
Both are within limits, with the landing margin (150 kg) tighter than the take-off margin (350 kg). The landing limit governed because the aircraft lands heavy relative to its limit on this short sector - most of the fuel is burned but the reserve is retained, and the landing limit (20,000 kg) is only 2,000 kg above the take-off limit's baseline relationship. The smaller of the two computed cargo allowances is the controlling one.