Fuel Decision During the Destination Hold
On a scheduled Boeing 737-800 service from Accra to Lagos with 148 passengers and 6 crew, the crew is told to hold at 12 000 ft, 25 NM from destination, because of a thunderstorm over the field. Fuel remaining at the start of the hold is 2 900 kg. Within that figure are an approach and landing allowance of 200 kg, alternate fuel of 900 kg for the nominated alternate 95 NM inland, and a final reserve of 1 200 kg (30 minutes at holding speed at 1 500 ft). Holding burns 2 000 kg per hour. ATC offers a second 20-minute hold. The alternate is now reporting a thunderstorm overhead with visibility 600 m and ceiling 100 ft; its only precision approach has minima of 200 ft and 800 m. The first officer says there are still 87 minutes of fuel, that the alternate is legally usable because published minima exist, and that MINIMUM FUEL only has to be mentioned on final approach.
1. Work out the fuel position if the second 20-minute hold is accepted, and state exactly what the crew should transmit to ATC and at what point.
Read the worked answer
Arithmetic. Holding flow is 2 000 kg/h, i.e. about 33 kg per minute.
- After the first 20-minute hold: 2 900 − 667 = 2 233 kg.
- Diverting now requires 900 + 1 200 = 2 100 kg, so only 133 kg (about 4 minutes) of margin remains: the alternate is already at the edge of reach.
- Accepting the second hold: 2 233 − 667 = 1 566 kg.
- Landing at destination requires 200 + 1 200 = 1 400 kg, leaving a margin of 166 kg, about 5 minutes.
Conclusion. After the second hold the aircraft cannot reach the alternate at all (needs 2 100 kg, has 1 566 kg). The flight is therefore committed to the destination, and any further change to the arrival - one more circuit, a go-around, a runway change - puts the landing fuel below the final reserve. That is precisely the ICAO definition of MINIMUM FUEL.
Transmission. On accepting the second hold, advise: "MINIMUM FUEL", with endurance/figures, e.g. "minimum fuel, 45 minutes, committed to Lagos". Do not wait for final approach; the value of the call is that it lets ATC sequence you ahead of other traffic while you still have options.
If the projected landing mass drops below the 1 200 kg final reserve, the call escalates to "MAYDAY MAYDAY MAYDAY FUEL", declaring an emergency and requesting priority to the nearest suitable aerodrome. The final reserve is a legal minimum, not a buffer to be spent in a hold.
2. The first officer argues the alternate is still legally usable because its minima are published and the thunderstorm is only temporary. Is he right, and what does this mean for the crew's earlier decisions?
Read the worked answer
No. A published approach does not make an aerodrome usable. The alternate must be expected to be usable at the estimated time of use, meeting the operator's planning minima (normally the approach minima plus the operator's margin). A thunderstorm overhead with 600 m visibility and a 100 ft ceiling is below the 200 ft / 800 m precision minima, and a TEMPO or a hopeful reading of the trend is not a basis for planning - a forecast improvement may only be used where it is a prevailing, not temporary, condition and the commander is satisfied it will hold.
Consequences. Once the alternate fell below minima, the flight effectively had no usable alternate. That is a change to the plan which must be resolved while fuel still allows it - either divert before the alternate becomes unreachable (at 2 233 kg there were only about 4 minutes of margin), obtain a new alternate within the available fuel, or hold with a pre-briefed limit and declare minimum fuel at that limit rather than after it.
Legal position. The commander has authority over the aircraft and responsibility for the fuel plan; alternate fuel is committed to reaching an alternate and cannot be treated as spare holding fuel. Burning it in a hold means the flight is being conducted without the diversion capability the flight plan assumed - a reportable safety occurrence, not merely a judgement call.
3. The aircraft eventually lands with 1 100 kg, below the final reserve. What must happen after landing?
Read the worked answer
Landing below the final reserve is an occurrence, not a routine outcome.
- Advise ATS if not already done: the crew should have declared MAYDAY FUEL before this point, and the landing should have been given priority.
- Record the facts: fuel at each decision point, hold times, the weather that made the alternate unusable, and the ATC clearances. The figures must be preserved before refuelling distorts them.
- Report to the operator into its safety management system, and to the Authority under the State's mandatory occurrence reporting system. Many States treat a landing below final reserve as a reportable serious incident because the barrier between the flight and fuel exhaustion had been removed.
- Technical log entry and a fuel-policy review by the operator: the chain here (alternate allowed to go below minima without action, holding accepted without a limit, MINIMUM FUEL deferred) is exactly what a fuel policy is written to prevent.
- Crew debrief: the decision that mattered was not the final approach but whether to accept the second hold at all.
The correct professional conclusion is that the flight was legal until the moment the alternate became unusable, and unsafe from then on.