Approach into Brunei with a Wind Shear Alert and a Wet Runway
You are on final approach to runway 03 at Brunei International Airport in the late afternoon. A thunderstorm has just passed, and the ATIS reports wind 030/18 kt gusting 30 kt, visibility 4000 m in rain, and a wet runway. The tower has issued a wind shear alert for the final approach. The aircraft's landing reference speed is 130 kt, and the crosswind limit is 15 kt. The runway is 3650 m long, and the landing distance required on a wet runway is 1400 m. The glideslope is 3°.
1. Interpret the wind shear alert and the gust spread, and decide whether to continue the approach or go around.
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The wind is 030/18 gusting 30 kt, so the gust spread is 12 kt. The wind shear alert indicates that the wind may change rapidly along the final approach. The crosswind component on runway 03 is 18 × sin(0°) = 0 kt, so the crosswind is not a factor. The gust spread of 12 kt means the airspeed may fluctuate by about half the gust spread, or 6 kt, which is manageable. However, a wind shear alert with a thunderstorm just passed means there may be a microburst or gust front on the approach. The safe decision is to go around, assess the situation, and either wait for the wind to settle or divert. Continuing the approach with a wind shear alert and a wet runway is not justified.
2. If you decide to land after a second approach, explain how the wet runway and the gusty wind affect your landing technique and the required distance.
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On a wet runway, the landing distance required increases because of reduced braking action and the risk of hydroplaning. The reported landing distance required is 1400 m, which is well within the 3650 m runway, so distance is not limiting. However, the gusty wind means the airspeed should be increased by half the gust spread, or 6 kt, to maintain a margin above the stall. The approach should be flown with a stabilized speed and a firm touchdown to avoid hydroplaning. Use full reverse thrust and brake gently to avoid skidding. If the wind shear alert continues, go around and divert.