Freezing Rain, a Contaminated Runway and a 30-Minute Alternate
A twin turboprop is planning an IFR flight to destination D, with alternate A. D’s TAF for the arrival period is: 300 ft broken, visibility 1,500 m, light freezing rain, temperature −2°C, dew point −3°C, wind 080/12 kt, QNH 1018. TEMPO 0500 freezing fog. Runway 08 has an ILS CAT I with DH 200 ft and RVR 550 m; landing distance available 2,000 m. The aircraft’s factored dry landing distance is 1,450 m; the operator uses a 1.35 factor for a contaminated runway with medium braking action. Alternate A is 30 minutes away, forecast 2,000 ft broken, visibility 10 km, temperature +2°C. The operator’s planning minima are: destination 600 ft ceiling and 3 km visibility; alternate precision approach 600 ft and 3 km, non-precision 800 ft and 3 km. The crew has fuel for one approach at D, a diversion to A, and 30 minutes final reserve.
1. Decode the destination weather and determine whether a destination alternate is required and whether A is legal.
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D has wind 080° at 12 kt, visibility 1,500 m, light freezing rain, broken cloud at 300 ft, overcast at 800 ft, temperature −2°C, dew point −3°C, QNH 1018. The temperature/dew point spread is 1°C, so fog or freezing fog is likely, and the TEMPO gives 500 m visibility in freezing fog. Freezing rain means ice accretion on the airframe and runway. The destination ceiling of 300 ft and visibility of 1,500 m are below the operator’s destination planning minima of 600 ft and 3 km, so a destination alternate is required. Alternate A forecasts 2,000 ft broken and 10 km, which meets the precision-approach planning minima of 600 ft and 3 km, and it is 30 minutes away. A is legal.
2. Calculate the contaminated landing distance and assess the landing decision at D.
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Contaminated landing distance = 1,450 × 1.35 = 1,957.5 m. LDA = 2,000 m, so the margin is only 42.5 m, about 2%. The reported ceiling of 300 ft and visibility of 1,500 m are above the ILS CAT I minima of DH 200 ft and RVR 550 m, so a landing is not automatically illegal. However, the margin is very small, freezing rain is continuing, braking action is only medium, and TEMPO freezing fog could reduce visibility below minima. The prudent decision is to divert to A or hold for a clear improvement. If the crew elects to land, they must fly a stable approach, use maximum braking and reverse as available, and be prepared to go around; but with fuel for only one approach, a go-around commits them to A.
3. If the crew goes around at D, what fuel and decision considerations apply?
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The go-around uses fuel that was not planned for a second approach. The crew has fuel for one approach at D, diversion to A, and 30 minutes final reserve; after a go-around, the diversion fuel becomes the planned fuel to A, but the final reserve must remain intact. The crew should not attempt a second approach at D unless the fuel situation is recalculated and a legal alternate is still available. The correct decision is to proceed to A, declare a fuel situation if the margin is tight, and land with at least the final reserve. If A’s weather deteriorates en route, the crew must consider another alternate before the fuel becomes critical.