Gust front on arrival: crosswind, landing distance and fuel
You are approaching destination X (elevation 1 500 ft) at 14:05 UTC with 3 200 kg of fuel remaining at the initial approach fix. Runway 09/27 is 2 400 m with a CAT I ILS on 27; runway 15/33 is 3 000 m with no ILS. The METAR reads 091250Z 25018G42KT 220V290 6000 TSRA SCT012 BKN025CB 18/16 Q1003, and the TAF adds TEMPO 0912/0918 25035G55KT 2000 +TSRA BKN008CB. Your operator's crosswind limit is 33 kt dry and 25 kt wet or contaminated. The runway is reported wet along its full length. Landing mass 65 800 kg; dry landing distance required 1 850 m; AFM wet factor 1.15. Your alternate is 25 minutes away and the final reserve is 30 minutes. Average burn in the hold and approach is 2 000 kg/h.
1. Calculate the crosswind components on both runways and decide which may be used.
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Wind 250° at 18 kt gusting 42 kt (TEMPO 35 gusting 55).
Runway 27 (270°), LDA 2 400 m:
- Angle 20° → crosswind 18 × sin 20° = 6.2 kt, headwind 16.9 kt.
- Gust: 42 × sin 20° = 14.4 kt. TEMPO: 55 × sin 20° = 18.8 kt.
- All below the 25 kt wet limit.
Runway 33 (330°), LDA 3 000 m:
- Angle 80° → crosswind 18 × sin 80° = 17.7 kt, headwind only 3.1 kt.
- Gust: 42 × sin 80° = 41.4 kt. TEMPO: 55 × sin 80° = 54.2 kt.
- These exceed 25 kt by a wide margin.
Decision: the longer runway 33 is unusable despite its greater length. Use runway 27, which also gives the ILS - valuable with a cumulonimbus overhead and rain. Apply the crosswind limit to the gust value, not just the mean wind.
2. Check the landing distance on runway 27 and state the margin. What else must be added before committing to the approach?
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Required landing distance = 1 850 × 1.15 = 2 128 m. Against LDA 2 400 m that leaves 272 m, about 11%.
Before committing, add these:
- Gust increment. With 18G42 the spread is 24 kt. Approach speed is increased by half the steady headwind plus the full gust increment, capped at Vref + 20 or VFE. A higher Vref lengthens the landing distance and spreads the touchdown point - the 272 m margin absorbs some of this, not all of it.
- Braking action. The 1.15 factor is the AFM wet factor, not a discretionary safety buffer. If the runway is later reported with standing water or poor braking action, the contaminated factor applies and the approach must be recomputed or abandoned.
- Runway state. The report says wet along the full length; a pilot report of aquaplaning on the first touchdown zone is a reason to go around rather than to brake harder.
If any of these pushes the required distance past 2 400 m, divert without a second approach.
3. With 3 200 kg at the IAF, decide whether to hold for the TEMPO to clear or to press on.
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The TEMPO runs 12–18 UTC. Arriving at 14:05 means up to four hours of exposure - holding for it to clear is not an option at any fuel state.
Fuel budget:
- Final reserve, 30 min at 2 000 kg/h = 1 000 kg
- Diversion, 25 min including climb and descent ≈ 1 000 kg
- Committed away from the destination ≈ 2 000 kg, leaving 1 200 kg for one approach and a go-around (about 400 kg) plus roughly 800 kg spare.
Decision: one approach to runway 27, with the go-around and the diversion fully briefed before the IAF. If the approach is not stable by 1 000 ft, or a go-around is flown, divert immediately - no second approach, no hold, and refuse any ATC delay of more than a few minutes. Landing with less than the final reserve is not a discretionary option.