Hot and High Takeoff with Contaminated Runway
At Kano at 14:30 local time, the Flight Engineer of a Boeing 727-200F is reviewing takeoff data. Outside air temperature is 41°C, QNH 1008 hPa, wind calm. Runway 24 is 3,000 m long, dry except for a patch of loose harmattan sand near the touchdown zone; braking action is reported as medium. The AFM contaminated-runway factor for this condition is 0.92 of the dry field-length limit. The dry field limit at the planned flap setting is 78,000 kg. Planned takeoff weight is 76,800 kg, and the planned fuel is 6,400 kg. The dispatcher's release shows the same figures but no contaminated-runway correction. The commander says the aircraft will 'get off before the sand' and wants to depart on time because the cargo has a connection in Lagos.
1. Using the data given, determine whether the planned takeoff weight is acceptable. Show your calculation and state the operational decision.
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The dry field limit is 78,000 kg. The contaminated-runway factor is 0.92, so the corrected field limit is:
78,000 × 0.92 = 71,760 kg.
The planned takeoff weight is 76,800 kg, which exceeds the corrected limit by:
76,800 − 71,760 = 5,040 kg.
The planned weight is therefore not acceptable for the contaminated runway. The commander's belief that the aircraft will 'get off before the sand' is not performance data and cannot be used instead of the AFM correction.
The FE should advise the commander and dispatcher that the takeoff weight must be reduced to 71,760 kg or less, or that the takeoff must be delayed until the runway is cleared or temperature/conditions improve enough to produce a valid limit above 76,800 kg. A different runway or flap setting could be considered only if supported by approved performance data.
2. Beyond field length, what other performance and operational factors should the FE check before accepting any revised takeoff data?
Read the worked answer
The FE should not stop at the field-length arithmetic.
- Obstacle clearance and climb: Check the net takeoff flight path, especially with high temperature and possible downdraughts, and confirm that obstacle gradients are met.
- Brake energy and tire speed: A contaminated runway may require a lower V1 and higher brake energy; confirm limits are not exceeded.
- V speeds: Recompute V1, VR and V2 for the actual weight, temperature, pressure altitude and runway condition.
- Runway slope, wind and contamination drift: Loose sand can reduce acceleration and braking; confirm the reported condition still matches the AFM factor.
- Engine failure case: Confirm the aircraft can stop or continue safely after V1 with the remaining runway and contamination.
- Landing performance at destination: Check that the planned fuel does not produce a landing weight beyond the destination runway limit.
- Crew and aircraft status: Confirm no MEL item affects performance and that the crew is not fatigued by the delay.
3. If the commander decides to wait for cooler evening temperatures, what new considerations arise for the Flight Engineer and the operator?
Read the worked answer
Waiting changes the performance calculation and the operational risk profile.
- The FE must obtain a new temperature, QNH and runway-condition report at the revised departure time; the earlier 41°C data cannot be reused.
- Evening departure may introduce night operations, runway lighting, noise restrictions and different alternates. The crew's duty and fatigue status must be recalculated.
- If the delay is long, the operator must consider crew rest, cargo security, fuel uplift and slot requirements.
- The runway may be cleared of sand, which would allow the dry limit again, but only if an authorised inspection confirms the surface condition.
The FE should record the revised data and ensure the final release reflects the actual conditions, not the original dispatch figures.