Runway selection and crosswind at Nampula
You are on final for runway 05 at Nampula (FQNP) in a Cessna 172, with a reported wind of 120° magnetic at 18 kt gusting 26 kt. The runway is 2,000 m of dry asphalt, elevation 1,440 ft. The aircraft's demonstrated maximum crosswind component is 15 kt. The tower offers you runway 23 instead, which is the reciprocal. There is no other runway. You are 3 NM final at 90 kt, with 1,200 ft to lose.
1. Compute the crosswind and headwind components for runway 05 and decide whether the approach is within limits.
Read the worked answer
Components for runway 05 (heading 050°). Wind 120° − runway 050° = 70° off the nose.
- Headwind = 18 × cos 70° = 18 × 0.342 ≈ 6 kt (gust 26 × 0.342 ≈ 9 kt)
- Crosswind = 18 × sin 70° = 18 × 0.940 ≈ 17 kt (gust 26 × 0.940 ≈ 24 kt)
Verdict. The steady crosswind of ~17 kt already exceeds the 15 kt demonstrated maximum, and the gust component of ~24 kt is far beyond it. Runway 05 is not within limits - this is a go-around, not an approach to continue.
2. Evaluate runway 23 as an alternative and state your decision and the radio call you would make.
Read the worked answer
Runway 23 (heading 230°). Wind 120° − 230° = −110°, i.e. 110° off the nose, effectively a 70° tailwind component.
- Tailwind = 18 × cos 70° ≈ 6 kt (gust ~9 kt)
- Crosswind = 18 × sin 70° ≈ 17 kt (gust ~24 kt)
Verdict. Runway 23 gives you a tailwind on landing and the same excessive crosswind. It is worse than 05, not better. Neither runway is usable within the aircraft's demonstrated crosswind limit.
Decision. Go around, climb to a safe altitude, and either hold for the wind to ease or divert to an aerodrome with a more favourable runway. Do not attempt a landing that exceeds the demonstrated crosswind - the limit exists because control authority at low speed is marginal.
Radio call. "Nampula Tower, [callsign], going around, request holding instructions and current wind." Then, once established: "[Callsign] would like to divert to [alternate], request vectors and weather." State the reason plainly: crosswind exceeds aircraft limits.