Convoy to the Forward Base: Fuel Reserve, Ferry and Departure Time
Your logistics cell must move 18 tonnes of supplies from Nampula to a forward base 480 km away. Six 5-tonne trucks are available; each carries 3 tonnes and burns 0.35 L of diesel per km whether loaded or empty. Each tank holds 200 L. Unit standing orders require arrival with at least 20 percent of tank capacity remaining. A fuel point at km 300 holds 600 L of diesel and can serve vehicles one at a time, 15 minutes each. A ferry at km 210 crosses in 20 minutes one way and carries two trucks per trip. Convoys travel at 40 km/h and must arrive by 18:00. The operations officer wants to depart at 05:00 without refuelling. One driver reports that the ferry queue is often 40 minutes long at that hour. You must decide whether to approve the plan and propose an alternative.
1. Can the convoy complete the move on one tank and still meet the 20 percent reserve rule?
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Route consumption per truck is 480 km × 0.35 L/km = 168 L. At arrival each truck would hold 200 − 168 = 32 L, which is 16 percent of 200 L, below the required 40 L (20 percent). The shortfall is 8 L per truck, or 48 L for six trucks.
At km 300 each truck has used 300 × 0.35 = 105 L and holds 95 L. The remaining 180 km needs 180 × 0.35 = 63 L, leaving 32 L. A top-up of 8 L gives exactly 40 L on arrival. The fuel point holds 600 L, so 48 L is available.
Conclusion: one tank is not compliant. Refuelling at km 300 is mandatory. A formal waiver of the reserve rule is possible in theory but unwise, because the final 180 km has no fuel point and a breakdown or detour would consume the margin.
2. Calculate the earliest departure time that meets the 18:00 arrival requirement, including ferry and refuelling delays.
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Driving time: 480 km ÷ 40 km/h = 12 h.
Ferry: six trucks at two per trip means three forward crossings and two return crossings, so five crossings × 20 min = 100 min. Adding the reported 40-minute queue gives 140 min.
Refuelling: six trucks × 15 min = 90 min, assuming the fuel point is ready and vehicles are marshalled one behind the other.
Total: 12 h + 140 min + 90 min = 12 h + 230 min = 15 h 50 min. To arrive at 18:00, departure must be no later than 02:10.
A 05:00 departure would produce an arrival at about 20:50, so the operations officer's plan fails on both fuel and time.
3. What alternative should you propose, and what risks remain?
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Best option: pre-position fuel at km 300 the previous day with a bowser or a pickup carrying drums, or attach a fuel truck to the convoy. That removes the 90-minute refuelling stop and moves departure to about 03:40, which still meets 18:00 with a small margin.
Second option: send an advance party to hold a ferry slot and marshal the trucks, but a 40-minute queue may persist and cannot be guaranteed.
If neither is possible, depart at 02:10 with two relief drivers per truck to manage fatigue. Risks to flag: night driving on the first leg, the unreliability of a single fuel point, and the fact that the 20 percent reserve leaves little room for detours or congestion. The commander should approve the plan in writing, naming the fuel source and the reserve rule.