question bout reserve fuel

[Guest Cessnan1315efw]

Hey this may be a stupid question but how much reserve fuel should i have....i know its 30minutes at day 45minutes at night.....But 30minutes reserve to fly at FL410 or 30 minutes reserve to do holding patterns at 5000ft???? its a big differrence in how much fuel you need for that. What do you guys usally plan for...?

[rdb 44]

Hey Anthony,The manuals says 18000lbs/hour for contingency, but don't know what altitude it is based on. Seems to be something in the middle, not a 5000ft and not a FL400.If you don't mind i'll jump in with another ... hm ... puzzle. Today i've decided to take 747 on a EDDM - EHAM route. Usually i use fuel planner by Skierr, but this time i've challenged myself with hand made fuel calculations. Here are some details:EDDM-EHAMDistance: ~400 nmCruise FL: 360Alternate: ~100 nm (EBBR)ZFW: 269,500 kgAs i was high on ZFW the Planned landing weight vs Max landing weight problem came up, so i've decided to round the figures down rather than up.ZFW: 269,500 kgMinimum landing fuel: 8,600 kgAlternate fuel: 3,600 kgContingency fuel: 4,000 kg---Planned landing weight: 285,700 kg (Max landing weight being 285,763!)Flight plan fuel (400 nm, interpolation of FL350 and FL370): 16,100 kgThere was a headwind of aprox. 20 kts enroute, but i've decided to not to take this into account because of Max Land Weight (first time headwind being of some help :7)As the planning chart says it's for planned landing weight of 216,000 kg, i've done some corrections. I believe this is the part i may have done some calculation errors.PLW: 285,700 kg - 216,000 kg--- 69,700 kg (lets assume 70 kg)Chart says to adjust aprox 420 kg/hour every 4,500 kg above 216,000 kg 70,000 / 4,500 = ~1515 * 420 kg = 6,300 kgSo the total figure:Planned landing weight: 285,700 kgFlight planned fuel: 16,100 + 6,300 = 28,700 kgTotal fuel: 45,000 kgWell...here comes the mystery...The problem is i've ended up overhead ARTIP (30 nm from Schiphol) with nearly 30 tons of fuel, that's about 10 tons (!) more than planned and overweight for landing...had to use those jettison nozzles :-shy What am i doing wrong here? :-zhelp