Crosswind Landing with a Contaminated Runway
You are landing a light single (MTOW 1,100 kg, wing span 10.7 m) on a 1,400 m runway, surface reported as compacted snow with a braking action of medium to poor. The tower reports wind 250/18 gusting 26, runway 27, temperature −3°C. The aircraft has a clean stall speed of 48 KCAS and a demonstrated crosswind component of 15 kt. The pilot plans a flapless approach at 65 KIAS because of the snow, with a 10 kt gust margin. There is a 0.5% downslope and a 200 m displaced threshold. The pilot's technique is to hold a crab until the flare and then kick off the drift.
1. Compute the crosswind and gust components and decide whether the landing is within limits.
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The wind is 250° and the runway is 270°, so the angle is 20°. The crosswind component at the mean wind is 18 × sin(20°) ≈ 6.2 kt; at the gust it is 26 × sin(20°) ≈ 8.9 kt. Both are well inside the 15 kt demonstrated crosswind, so the crosswind itself is not limiting. The headwind component is 18 × cos(20°) ≈ 16.9 kt, gusting to 24.4 kt. The gust spread is 8 kt, so a gust margin of half the spread (4 kt) or the full spread (8 kt) is appropriate; the planned 10 kt margin covers it. The real limit is the braking action and the runway length, not the wind. The landing is within the crosswind limit but the stopping distance must be checked against the contaminated surface.
2. Assess the stopping distance on the snow and the effect of the displaced threshold and downslope.
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On compacted snow with medium-to-poor braking, the friction coefficient may be roughly 0.2–0.3, compared with 0.5 or more on dry asphalt, so the landing roll is substantially longer. At 65 KIAS the ground speed at touchdown in a 17 kt headwind is about 48 kt, but the aircraft must still be stopped in the available distance. The displaced threshold removes 200 m, leaving 1,200 m of landing distance available; the 0.5% downslope adds to the roll. A conservative planning figure for a light single on snow is 1.5–2 times the dry distance, so if the dry landing distance is around 500 m, the snow figure could be 750–1,000 m, which fits within 1,200 m but with little margin if the braking action is poorer than reported. The correct decision is to fly a stabilised approach with full flap if the snow allows, aim to touch down early, and be prepared to go around if the aircraft is not decelerating.
3. Critique the planned flapless approach and the crab-and-kick technique in this wind.
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A flapless approach raises the approach speed and reduces drag, which lengthens the float and the landing roll - exactly what a contaminated runway does not want. The reason usually given is that flaps can pick up snow or that a flap asymmetry is possible, but on a light single with a clean wing the better trade is normally full flap for the shortest roll, provided the flaps are checked after touchdown. The 65 KIAS target is reasonable for a flapless approach, but the gust margin should be based on the gust spread and added to the approach speed, not treated as a fixed 10 kt. The crab-and-kick technique is acceptable in a 6–9 kt crosswind, but on a slippery surface the kick must be gentle and the touchdown positive, because a firm arrival reduces the risk of aquaplaning-like skidding on snow. A wing-low approach may be preferable to keep the into-wind wing down and counter drift without a large yaw input at the flare. Be ready to go around: on snow, a rejected landing is safer than a long float.