Fuel and endurance calculator

1. Groundspeed out = 188.4 kt and groundspeed home = 229.3 kt, both solved as wind triangles on track 153 and its reciprocal, at 210 kt true in a 30 kt wind from 200.
2. Usable fuel = 1000 - 200 = 800. Safe endurance = 800 / 180 = 4.4 hours, which is 4 h 27 min.
3. Still air range = total endurance x TAS = 5.6 x 210 = 1166.67 nm. This uses ALL the fuel including the reserve, so it is a performance figure and not a distance you may plan to fly.
4. PNR = endurance x O x H / (O + H) = 4.4 x 188.4 x 229.3 / 417.7 = 459.65 nm, reached at 2 h 26 min.
5. CP = D x H / (O + H) = 925 x 229.3 / 417.7 = 507.81 nm, reached at 2 h 42 min. The CP does not depend on how much fuel you carry, only on the two groundspeeds and the distance.
6. Fuel to the destination = 180 x 925 / 188.4 = 883.8, against 800 usable.

Exam trap: the critical point does not depend on how much fuel you carry at all, only on the distance and the two groundspeeds. The point of no return depends on the fuel and not on the distance. A question that changes the fuel and asks what happened to the CP is asking whether you know that.

The units are yours. Kilograms, pounds or gallons all work, as long as the flow is in the same unit per hour, which is why no unit is printed beside the fuel figures above.