Fuel and range in real life

[forthbridge]

Quick question: obviously maximum range on any aircraft is almost infinitely variable depending on conditions.....


But, assuming it takes xx kilos of fuel to lift xx kilos of payload a given distance 'up'.... would and aircraft 'A' loaded with xx kilos less fuel than Aircraft 'B' (thus theoretically burning less to get to altitude) - have a similar range with less fuel? Are margins enough to allow that to happen, or not significant enough to make much difference?
For weight I'm considering an identical non-fuelled payload weight, or empty A/C

[NigelC]

In theory yes. There is a fuel burn penalty for tanking extra gas, and I used to have a formula that you could use to determine if it was worthwhile tanking against fuel price cost index at destination. i.e. if the fuel was marginally more expensive, it may be worth paying the extra against the burn penalty of lugging a few extra tonnes around.

You still can't get round the EU-OPS Subpart D requirements for minimum fuel required for a sector.

Planning figures tend to be based around a mid-cruise weight.

Think the margins are going to be slim though, if tou take 500kg less fuel, on a One Eleven for example, you're going to come up about 15mins/100nm shorter. But the saving in fuel burn isn't going to gain that back again. On a three hour trip, you're going to burn about 7000kg, even if you saved as much as 5%, that's only 350kg - 10 mins/70nm and I doubt if the saving would be that great.

That's just a few quick thoughts off the top of my head after a few G & T's.

If in doubt, stick to the Subpart D fuel planning requirements, plan for somewhere shorter, do your en-route howgozit checks and re-clear in flight if your ahead of the curve.

Nige

[DaveB]

Yup.. that is, agreeing with Nigel When you're talking of calculating around 200kg for startup and taxi (depending on aircraft).. an off the shelf figure as Nigel quoted of 350kg (if that) wouldn't matter much in the grand scale of things I've heard on more than one occassion that a captain would consider any additional fuel in tonnes/tons rather than the consequences of saving such a short amount of fuel ;-)

Unless you're flying into a hurricane, your VC10 WILL get you to ASI

ATB

DaveB :tab:

[cstorey]

Generally speaking, as a rule of thumb, in a fanjet aircraft cruising at FL 300 or above, every extra kg of fuel you lift will cost you about 0.3 kg in fuel consumed . Thus if you carry less fuel than optimum, you lose about 70% of the range which that fuel would have given you