Old Chart, New Airspace, Tight Fuel
You are planning a 118 NM VFR flight in a light single. Usable fuel 18 US gal, cruise consumption 9 gph, TAS 100 kt; the forecast gives 95 kt ground speed. Planned departure 1230 local, ETA about 1345. The chart you are using is the previous edition, two years old. The pre-flight briefing shows: a parachute dropping area, surface to FL120, active 1200–1900 local, centred 12 NM south of your track midpoint; and an AIP supplement establishing a new Class D control zone with a base of 2000 ft above aerodrome level, whose boundary runs 3 NM right of your planned track beyond the 40 NM point. Destination TAF includes TEMPO 1400–1700, 3000 m in mist, broken cloud at 800 ft. The nominated alternate is 22 NM away and forecast clear.
1. What must you verify from publications before this flight can be flown as planned, and what does each item actually change?
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Three separate publication problems, each with a different fix:
1. Chart currency. The chart is the previous edition, so it cannot be assumed to show current airspace. Check the chart's edition date and amendment number against the current AIP/chart amendment list, and read the briefing NOTAMs and AIP supplements in full rather than relying on the chart. A new control zone created by supplement will not appear on an old chart at all.
2. The new Class D zone. Its base is 2000 ft AAL and its boundary runs 3 NM right of track beyond 40 NM. Two consequences: at a cruise level above 2000 ft AAL you are inside controlled airspace and need a clearance, so either plan a cruise level below the base (terrain and minimum-height permitting) with a clear vertical margin, or plan to route further left. "Three miles to the right" is not a margin - normal navigation tolerance and any right-hand drift will eat it, and you will not see the boundary.
3. The dropping area. It is 12 NM south of track, so it does not affect the planned route, but its vertical extent (surface to FL120) means there is no overflight option if you are diverted south. Note its active period; it starts before your ETA.
Finally, confirm the destination aerodrome and alternate status (serviceability, hours, PPR if required) in the same briefing, and note which frequency/ATZ details have changed.
2. Work the fuel figures and decide whether the flight, with an alternate, is a sensible plan.
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Endurance. 18 gal ÷ 9 gph = 2.0 hours total, with no allowance for taxi, climb, or leaning errors.
Trip. 118 NM at 95 kt = 1.24 h, i.e. about 1 h 14 min.
Reserve. Day VFR reserve is 30 minutes, i.e. 0.5 h = 4.5 gal.
Total committed. 1.24 + 0.5 = 1.74 h, or 87% of endurance. That leaves 0.26 h - about 15 minutes - as the entire unplanned margin.
Add the alternate. 22 NM at 95 kt = 14 minutes. That consumes essentially the whole 15-minute margin. If the destination goes below VMC while you are overhead, you have enough fuel to divert only if nothing else goes wrong: no hold, no vectoring, no headwind, no go-around.
Conclusion. The plan is not robust. Options, in order of preference: reduce the problem by using an alternate closer than 22 NM or by carrying more fuel if payload allows; plan a fuel stop; or accept a shorter leg. Do not "solve" it by planning to land with less than the reserve - the reserve is what protects you when the TEMPO actually happens.
3. The TEMPO group covers your ETA window. How does that affect the go/no-go decision and your in-flight criteria?
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What the forecast means. TEMPO 3000 m in mist, broken at 800 ft is intermittent but plausible, and it coincides with your arrival. In Class D at your likely level (below 10,000 ft), VMC minima are 5 km flight visibility with 1500 m horizontally and 1000 ft vertically from cloud. 3000 m is below 5 km, so during a TEMPO period the aerodrome is not usable for VFR arrival, and broken cloud at 800 ft leaves no room to descend visually and stay clear.
Planning consequences.
- You cannot plan to arrive and simply "see how it looks". Either plan to arrive outside the TEMPO window, or carry fuel and a firm alternate that is genuinely clear.
- Because the alternate is 22 NM away and the fuel margin is 15 minutes, the weather and the fuel problems are the same problem. Fixing one without the other does not make the flight safe.
In-flight criteria, decided on the ground. Before departure, write down the point at which you turn back or divert: for example, if the destination ATIS or the approach controller reports visibility below 5 km, or cloud base below 1000 ft, you divert without entering the terminal area. Decide the diversion trigger while you still have fuel and options, not while overhead with 15 minutes of margin.