Diversion Decision with Fuel and Weather Pressure

Fuel on board is 95 litres. Cruise burn 38 L/h means 95 litres gives 95/38 = 2.50 h, i.e. 150 minutes of endurance at cruise.

Reserve requirement: 45 minutes at 38 L/h = 28.5 litres. Usable fuel above reserve is 95 − 28.5 = 66.5 litres, giving 66.5/38 = 1.75 h = 105 minutes of 'planning' endurance.

Continue to destination: 70 NM at 120 KT = 35 minutes. That leaves 150 − 35 = 115 minutes total remaining, comfortably above the 45-minute reserve.

Divert to the ILS airport: 110 NM at 120 KT = 55 minutes. Remaining after diversion = 150 − 55 = 95 minutes, still above reserve, plus an approach and possible hold of perhaps 10–15 minutes. Still workable on fuel.

So fuel does not force the decision - both options are legal on fuel. The deciding factors are weather, daylight and capability: broken cloud at 1,800 ft with deteriorating visibility at a strip with no approach and no lighting, arriving near or after sunset, in an aircraft flown by a VFR-only pilot. The defensible choice is the diversion to the ILS airport while fuel and daylight remain, because it preserves options; continuing commits you to a destination where a go-around means a forced landing in fading light.

Legal minima are a floor set for the least demanding case; they are not a guarantee that a flight can be completed safely. Several factors here degrade the margin between the legal minimum and the practical requirement:

• Blowing dust reduces slant visibility and makes the runway and surface features hard to distinguish, particularly into sun or in low light. Reported horizontal visibility at a station is not the same as what you see on final approach.
• Broken cloud at 1,800 ft is close to the height at which a VFR pilot must remain clear of cloud. Any sink or terrain rise reduces separation quickly, and there is no approach aid to follow if the cloud base lowers.
• The forecast is deteriorating, not improving, so the conditions you plan for are the best case, not the expected case.
• Sunset in 50 minutes means the arrival is at or after last light, with no lighting at the strip. Depth perception and obstacle recognition degrade markedly, and a go-around becomes a night diversion from low level.
• There is no instrument approach and the pilot is not instrument rated, so there is no recovery path if visual reference is lost.

The correct reasoning is to treat the legal minimum as one input alongside trend, light, pilot capability, aircraft equipment and escape options. A flight that is legal but leaves no margin for a single unexpected event is not a sound command decision.

Before turning, the pilot should stabilise the situation: note the time and position, confirm fuel by checking gauges and any dip or totaliser figures, and recompute endurance for the new route including an approach and a hold. Then:

1. Inform ATC promptly - declare the intention to divert, give present position, heading, altitude, endurance and the requested airport. ATC can then provide traffic information, a direct routing and expected approach type.
2. Obtain the destination weather and airfield information: runway in use, circuit direction, radio frequency, and any notified restrictions. Confirm the airport accepts the aircraft type and that you can pay/handle there.
3. Re-plan navigation: set the new track, note distance and time (110 NM, 55 minutes), identify en-route hazards and any controlled airspace boundaries crossed, and set a fuel 'bingo' point at which you would commit to a further alternate.
4. Brief yourself for the approach: expected join, altimeter setting, missed approach intentions given VFR-only capability, and what you will do if the weather at the diversion is also below your personal limits.
5. Advise the destination strip by radio or telephone if practicable so nobody is waiting or searching.
6. Monitor fuel and weather continuously and be prepared to declare an emergency early if either deteriorates; declaring early gives ATC time to help.