Dawn Departure from Bandar Seri Begawan with Fog and a Tight Fuel Margin
It is 0540 local time at Brunei International Airport (WBSB). Your CPL flight test departure is scheduled for 0600. The 0500 METAR reads: WBSB 292100Z 00000KT 1200 BR FEW003 SCT015 24/24 Q1012. The TAF for the period expects visibility to improve to 8000 m with FEW015 by 0700. The aircraft has no autopilot and no de-icing equipment. Your examiner asks you to plan the departure. The route requires a 25-minute climb to 9000 ft before entering controlled airspace, and the aircraft's single VOR receiver is serviceable. The aerodrome has a 30 m elevation and a surrounding terrain rise to 200 ft within 5 NM. You must decide whether to depart at 0600 or delay, and how to brief the take-off and initial climb.
1. Interpret the 0500 METAR and decide whether the 0600 departure is acceptable. Explain how you use the reported visibility, cloud base, and the TAF trend in your decision.
Read the worked answer
The METAR shows calm wind, visibility 1200 m in mist, a few clouds at 300 ft, scattered cloud at 1500 ft, temperature and dewpoint both 24°C, and QNH 1012 hPa. The temperature/dewpoint spread is zero, so the air is saturated and fog or very low mist is likely to persist until insolation or mixing lifts it. Visibility of 1200 m is below the typical 1500 m take-off minimum for a commercial operation, and the 300 ft cloud base is close to the 200 ft terrain within 5 NM. The TAF improvement to 8000 m and FEW015 by 0700 is a forecast, not an observation, and it is 60 minutes after the planned departure. The safe decision is to delay until a new METAR shows visibility at or above the operator's take-off minimum and a cloud base that clears the terrain by a safe margin. If the operator's minimum is 1500 m, wait for the 0600 or 0630 observation; if it is 1200 m with a suitable take-off alternate, the departure could be legal but the zero spread and calm wind argue for caution. A 0600 departure is not justified on the current observation alone.
2. Assuming you delay, describe the specific observations and reports you would monitor between 0600 and 0700, and what would make you cancel the flight entirely.
Read the worked answer
Monitor the half-hourly METARs for visibility trend, cloud base, and the temperature/dewpoint spread. A spread of 1°C or more with visibility improving to 3000 m or better indicates the mist is lifting. Check the TAF amendment and any aerodrome warning for fog. Also check the 0600 and 0630 SPECI if conditions change rapidly. Cancel the flight if visibility remains below the take-off minimum at 0700, if the cloud base falls below the terrain clearance requirement, or if the TAF is amended to show fog persisting past 0800. If a take-off alternate is required, confirm it is available and within the required distance. Do not depart on a forecast alone; require an actual observation that meets the minimum.