Fuel, alternate selection and the freight that pays for the trip
You are the single pilot of a Cessna 402C on a Part 135 charter from Port Moresby (AYPY) to Lae Nadzab (AYNZ) with five passengers and an unaccompanied freight consignment of 80 kg. Off-blocks is planned for 15:20, flight time 1:05 at 9,000 ft. Usable fuel after taxi gives 2 h 50 min at planned flow.
Forecast: AYNZ 30012KT 9999 -SHRA SCT018 BKN030 TEMPO 1600/1800 4000 SHRA BKN015. AYMD (Madang) 30010KT 9999 SCT020, no significant change. AYGA (Goroka) is forecast fine, but the ERSA entry shows no instrument approach and day operations only. Company alternate minima: AYNZ ceiling 1,500 ft and 8 km; AYMD ceiling 1,400 ft and 8 km. Madang is 0:40 from Nadzab; Goroka is 0:20. Sunset at Nadzab is 18:12.
The dispatcher argues that the TEMPO is 'only showers' and suggests naming Goroka as the alternate so that you keep the freight and save fuel.
1. Is a destination alternate required for this flight, and can Goroka be used?
Read the worked answer
Yes, an alternate is required - and Goroka cannot be it.
- The window that matters is one hour either side of ETA (15:25–17:25). The TEMPO 1600/1800 falls inside it, so the TEMPO conditions count.
- TEMPO BKN015 / 4000 m means a ceiling of 1,500 ft and 4 km. Against the company alternate minima for AYNZ (1,500 ft and 8 km) the visibility fails, so the destination is forecast below alternate minima during the window. A destination alternate is mandatory.
- An IFR alternate must let you carry out an instrument approach and land legally. Goroka has no published instrument approach and is day-only, so it is not a usable IFR alternate - that is a qualification problem, not a distance or fuel problem.
- Madang is the only listed alternate with an approach, and its forecast stays above its own alternate minima across the whole window.
Consequence: plan with Madang, which costs 20 minutes more than Goroka. The freight cannot justify naming an alternate that cannot legally serve as one; the dispatcher's suggestion is exactly the kind of commercial pressure this rule exists to stop.
2. Set out the fuel you must plan and decide whether the flight, as loaded, can legally depart.
Read the worked answer
IFR fuel planning under PNG Part 91 comprises:
- taxi fuel;
- trip fuel to the destination;
- approach and missed approach at the destination;
- fuel from destination to the alternate;
- 45 minutes holding at 1,500 ft above the alternate (or at holding speed if a higher level is required), plus any contingency the operator's exposition adds.
With Madang: 1:05 trip + 0:10 approach/missed + 0:40 alternate + 0:45 hold = 2:40 against 2:50 usable - 10 minutes of margin.
That is legal on paper, but 10 minutes is not a buffer. The 45 minutes is a final reserve, not cruise fuel to be traded for freight, and the 10 minutes must absorb an ATC delay at Moresby, a deviation around build-ups, extra time in cloud in a single-pilot aircraft with no autopilot, and possibly a second approach at Madang. If the 80 kg cannot be shown to leave every one of those components intact after re-planning, it comes off. Make that decision on the ground, not over the ranges.
3. At 15:55, 20 nm west of Nadzab, ATC passes a special for AYNZ: 2500 m, BKN008. You are still in cloud at 9,000 ft. What do you do?
Read the worked answer
Before descending, settle three things: the fuel needed to divert plus the 45-minute reserve, the actual approach minima at Nadzab, and how many approach attempts you can afford.
- 2,500 m and BKN008 is below the company alternate minima and may be at or below the approach minima. Check the AIP chart: if the ceiling is below minima, there is no point starting.
- One approach is reasonable only if the reported conditions are at or above minima and you keep the alternate fuel unbroken. You should not descend below minima on the chance of a break, and you should not begin an approach that leaves you at the missed-approach point without alternate fuel plus reserve.
- If the conditions are below minima, or a second approach would eat the reserve, divert to Madang now, advise ATC and operations, and land with the reserve intact.
A landing at Madang with fuel in hand is an inconvenience. A diversion from a diversion, in cloud, in the ranges, is an occurrence. Decide early, while both options are still open.