Extra fuel burn per passenger
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Extra fuel burn per passenger
I have a very hazy memory about reading an article some forty years ago, saying that a ten pound briefcase loaded onto a VC10 would cause an extra fuel burn of half a pound per hour of flight. I know that airliners are much more fuel efficient these days, but can anyone tell me how much extra fuel is used per passenger these days?
For simplicity, let's say it's a fairly fat passenger weighing two hundred pounds. This question has been bugging me for some time now & I would really appreciate an answer.
For simplicity, let's say it's a fairly fat passenger weighing two hundred pounds. This question has been bugging me for some time now & I would really appreciate an answer.
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What if it is a fairly lean passenger weighing two hundred pounds? Your bias should be bugging you for some time.
Oh BTW, the ten pound briefcase would weigh the same, regardless of the BMI of the two hundred pound passenger.
Oh BTW, the ten pound briefcase would weigh the same, regardless of the BMI of the two hundred pound passenger.
An air carrier I serviced in the early 1960's at KJFK was operating B.720 trans-Atlantic. They had JT3C non-fan engines and were marginal as far as their range for that service. They also suffered from usually carrying full pax loads being very popular with one particular ethnic group in New York. As a result we (maintenance) had to drip-stick the fuel on board to get an accurate quantity taking pitch and roll in consideration and had to check the density of the fuel on board and of the uplift fuel.
We were given the desired total fuel load, like 42,386 kilos. They had weighed the baggage and a good idea of the pax weights and the resulting fuel load was the difference between aircraft, pax and baggage weight and the MTOW. Using graphs and charts we calculated the uplift to the gallon. Literally, every extra kilo of pax or baggage meant one less kilo of fuel and a possible fuel stop. Marginal indeed.
We were given the desired total fuel load, like 42,386 kilos. They had weighed the baggage and a good idea of the pax weights and the resulting fuel load was the difference between aircraft, pax and baggage weight and the MTOW. Using graphs and charts we calculated the uplift to the gallon. Literally, every extra kilo of pax or baggage meant one less kilo of fuel and a possible fuel stop. Marginal indeed.
For a large jet-transport, a useful rule of thumb is that any extra weight carried will result in an extra fuel burn of 4% of that weight per hour.
So, for your example, and extra 200lbs will result in approximately 8lbs per hour of extra fuel burn.
I’m not sure if this rule of thumb applies for such small increments.
It does for large weights: e.g. on the 747-400, carrying an extra 10 tonnes of fuel for a 10 hour flight would result in only 6 tonnes extra remaining at destination.
So, for your example, and extra 200lbs will result in approximately 8lbs per hour of extra fuel burn.
I’m not sure if this rule of thumb applies for such small increments.
It does for large weights: e.g. on the 747-400, carrying an extra 10 tonnes of fuel for a 10 hour flight would result in only 6 tonnes extra remaining at destination.
You mean because the aircraft doesn't notice small increments until enough of them have been added and it finally wakes up to the fact ? 
I think it's safe to assume that as a rule-of-thumb, it applies pro rata as soon as you start adding any weight.
I think it's safe to assume that as a rule-of-thumb, it applies pro rata as soon as you start adding any weight.
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And added weight includes fuel so on a longer flight the aircraft burns more fuel to tanker the fuel required to support any extra weight!
I agree that any extra weight increases fuel burn but I’m not sure that the “4%” figure applies to relatively tiny increments. Nor may it apply to huge increments. It’s a rule of thumb for “normal” weight adjustments (e.g. plus or minus 10 tonnes for a 747).
On the other hand, maybe it’s super-accurate at all weights but I suspect not.
On the other hand, maybe it’s super-accurate at all weights but I suspect not.
For a large jet-transport, a useful rule of thumb is that any extra weight carried will result in an extra fuel burn of 4% of that weight per hour.
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In my day some said 4% per hour, some said 6% for the first hour then 3% per hour thereafter but certainly with jets we had computerised flight planning to work all this out for us.
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"Duty-Free" Bottles.
Many years ago someone crunched the numbers for the extra fuel burn carrying bottles of booze, some of them glass, on long-haul operations just so's the CC could sell them to pax and hopefully supplement their meagre earnings after Airline profit.
The conclusion was considerable extra burn, per annum. per fleet, per company. The proposed solution; why not allow the pax to purchase at destination as they disembarked but still in a customs-controlled environment?
Allegedly when this was put to the nations various, it was considered all too difficult and so the practice of ferrying bottles of Mothers' Ruin backwards and forwards over the ponds continued during all the fuel crises since the 1974 OPEC wake-up call.
3% extra per hour per extra unit of weight/mass carried seems to be the norm for modern fuel-efficient 'frames and under the laws of physics we have to accept it takes effect as soon as that 1 kilogram or 1 pound steps or is loaded aboard.
Fat-
-tax is the thought which has occurred to all of us as we've watched decoys for the whaling fleet getting a clear run past the check-in desk as our sylph-like selves/companions get hammered for extra payment because the cabin/checked bag is a tad over the specified amount.
Maybe it's time to introduce a pax+baggage weighbridge with approporiate surcharges but doubtless the human rights brigade would howl it down?
The conclusion was considerable extra burn, per annum. per fleet, per company. The proposed solution; why not allow the pax to purchase at destination as they disembarked but still in a customs-controlled environment?
Allegedly when this was put to the nations various, it was considered all too difficult and so the practice of ferrying bottles of Mothers' Ruin backwards and forwards over the ponds continued during all the fuel crises since the 1974 OPEC wake-up call.
3% extra per hour per extra unit of weight/mass carried seems to be the norm for modern fuel-efficient 'frames and under the laws of physics we have to accept it takes effect as soon as that 1 kilogram or 1 pound steps or is loaded aboard.
Fat-
-tax is the thought which has occurred to all of us as we've watched decoys for the whaling fleet getting a clear run past the check-in desk as our sylph-like selves/companions get hammered for extra payment because the cabin/checked bag is a tad over the specified amount.Maybe it's time to introduce a pax+baggage weighbridge with approporiate surcharges but doubtless the human rights brigade would howl it down?
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Going back decades Britannia calculated the fuel cost for adding one large orange to their in-flight meals ... they diidn't add the orange 
If any of you ever saw the TV programme 'Sky Truckers' featuring 'Cargo Lion', the crew were in a hotel bar, how unusual, and the F/E 'Trenty' was telling the story of one flight transporting elephants when at the last minute loads of bales of hay arrived, as he announced "Right, these have to be added to the payload and the fuel recalculated" the groom in charge would simply not accept that they counted as payload as the elephants were going to eat them during the flight
Wow, I just found 'Sky Truckers' on youtube if anybody is interested, I was young (ish) when we made this and a lot of alcohol consumption went in to it
If any of you ever saw the TV programme 'Sky Truckers' featuring 'Cargo Lion', the crew were in a hotel bar, how unusual, and the F/E 'Trenty' was telling the story of one flight transporting elephants when at the last minute loads of bales of hay arrived, as he announced "Right, these have to be added to the payload and the fuel recalculated" the groom in charge would simply not accept that they counted as payload as the elephants were going to eat them during the flight
Wow, I just found 'Sky Truckers' on youtube if anybody is interested, I was young (ish) when we made this and a lot of alcohol consumption went in to it
Last edited by Harry Wayfarers; 7th Feb 2018 at 14:08.
6lb but only for the final hour of the flight, for the next plus last hour 6lb + 3% = 6.18lb, the hour before that 6.18lb + 3% etc. etc. etc.
In my day some said 4% per hour, some said 6% for the first hour then 3% per hour thereafter but certainly with jets we had computerised flight planning to work all this out for us.
In my day some said 4% per hour, some said 6% for the first hour then 3% per hour thereafter but certainly with jets we had computerised flight planning to work all this out for us.
Oh here we go again.
I suspect that Flight Idle is not carrying any additional weight on his body and feels he is due a rebate. Miss, miss, it's not fair he wails...............
When is the weight for fatties to be taken? At time of booking, which might be months ahead of the date of travel and therefore liable to be inaccurate by the time of the flight? Imagine the arguments at c-in when someone who has entered 50 kgs weight at the time of booking turns up to c-in and is 95 kgs!!
Or perhaps at check-in, causing even more time to be spent in the queues as the poor check-in agent asks everyone to stand on the scales? Should this be with coat and jacket on, or just down to shirt/blouse and trousers/dress/skirt? I can just imagine Mr and Mrs Blobby arriving at c-in with just their underwear covering them, then sneaking off to get dressed after c-in. What then? Re-weighing at the gate?
Hmmmm the B777-300, A380, B747 frequently have 400+ pax on board. People will have to take an extra days holiday to allow for processing time at the airport!!
Perhaps we could include height as another way the skinny short a*s*s could claim a lower fair. An additional charge per inch over 5' 8" for fellas and 5' 4" for the ladies.
Or we could continue to use a notional weight for males/females/children/infants and know that the total weight is likely to be within a certain figure depending on config and passenger load. This reduces the fannying around at check-in, keeps everyone in a reasonable frame of mind, and is very workable.
Perhaps there should be a 'Fat Passenger' surcharge if they're making the planes burn more fuel. I'm surprised Ryaniar haven't thought of that.
When is the weight for fatties to be taken? At time of booking, which might be months ahead of the date of travel and therefore liable to be inaccurate by the time of the flight? Imagine the arguments at c-in when someone who has entered 50 kgs weight at the time of booking turns up to c-in and is 95 kgs!!
Or perhaps at check-in, causing even more time to be spent in the queues as the poor check-in agent asks everyone to stand on the scales? Should this be with coat and jacket on, or just down to shirt/blouse and trousers/dress/skirt? I can just imagine Mr and Mrs Blobby arriving at c-in with just their underwear covering them, then sneaking off to get dressed after c-in. What then? Re-weighing at the gate?
Hmmmm the B777-300, A380, B747 frequently have 400+ pax on board. People will have to take an extra days holiday to allow for processing time at the airport!!
Perhaps we could include height as another way the skinny short a*s*s could claim a lower fair. An additional charge per inch over 5' 8" for fellas and 5' 4" for the ladies.
Or we could continue to use a notional weight for males/females/children/infants and know that the total weight is likely to be within a certain figure depending on config and passenger load. This reduces the fannying around at check-in, keeps everyone in a reasonable frame of mind, and is very workable.
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Going back decades Britannia calculated the fuel cost for adding one large orange to their in-flight meals ... they diidn't add the orange
I remember this. Give an accountant a calculator and anything is possible. The cost of the orange, and the delivery thereof, plus the teaspoon of fuel was all added together. The accountant crunched the numbers and I think claimed he had just paid his salary in one foul swoop.
I remember this. Give an accountant a calculator and anything is possible. The cost of the orange, and the delivery thereof, plus the teaspoon of fuel was all added together. The accountant crunched the numbers and I think claimed he had just paid his salary in one foul swoop.
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I am sure in the good old days of Ted Barff at Britannia,Accountants were not tolerated to make the inane suggestions that todays crews have to put up with!Let alone check w&bs of an extra Orange!!Makes me cringe to read whats going on these days.Getting bollocked for hand flying used to tickle me,especially when demonstrating dutch roll with the yaw dampers off on ferry flights!!!The good old days when stick and rudder guys were in charge,meant everyone was safe with or without the master and its slaves.Makes me kind of remember a certain "EA" spear in trying to turn too tight too heavy to catch up years ago!!
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Ah. TB, man and moustache who wintered at La Manga before the masses discovered it.
The good old days when stick and rudder guys were in charge,
And after the arrival of B767 Gorbachov referred to B732 as 'the fighter'. There have been so many threads repeating the same opinion about the wasting & disappearance of basic skills, on Rumours and Tech Log etc, and there is another one opening in 'Questions', that I expect the next repeating circular discussion will be side-lined to 'Aviation Nostalgia'.
The good old days when stick and rudder guys were in charge,
And after the arrival of B767 Gorbachov referred to B732 as 'the fighter'. There have been so many threads repeating the same opinion about the wasting & disappearance of basic skills, on Rumours and Tech Log etc, and there is another one opening in 'Questions', that I expect the next repeating circular discussion will be side-lined to 'Aviation Nostalgia'.