Extra fuel burn per passenger

[Flight_Idle]

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.

[evansb]

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.

[tonytales]

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.

[eckhard]

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.

[DaveReidUK]

I’m not sure if this rule of thumb applies for such small increments.

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 ? :O

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.

[Harry Wayfarers]

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 ? :O

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.

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!

[eckhard]

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.

[DaveReidUK]

On the other hand, maybe it’s super-accurate at all weights but I suspect not.

Quite so.

If it was a precise, fixed relationship, we wouldn't refer to it as a "rule-of-thumb". :O

[Flight_Idle]

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.

[kenparry]

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.

On the B767 we used to use 3% per hour. So your 200lb passenger would result in an extra 6lb per hour fuel burn.

[Harry Wayfarers]

On the B767 we used to use 3% per hour. So your 200lb passenger would result in an extra 6lb per hour fuel burn.

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.

[BARKINGMAD]

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-:mad:-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? :rolleyes:

[Harry Wayfarers]

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 :)

https://www.youtube.com/watch?v=gsNpOBGyV4A

[kenparry]

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.



Harry, that's not how we applied it. Just 3% x wt diff x hrs. It was limited to a defined change of gross weight; the precise figure I don't recall, but I think it was a couple of tonnes. For a greater weight change we would get a new computer flight plan.

[surely not]

Oh here we go again.

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.

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.

[RAT 5]

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.

[FAStoat]

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!!

[RAT 5]

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'.

[Cirrussy]

A321 fag packet calculation, 4kg fuel per 100kg pax per hour.

[RAT 5]

I seem to remember we used +3%/hr for overweight & -2%/hr for underweight.

[Harry Wayfarers]

A321 fag packet calculation, 4kg fuel per 100kg pax per hour.

Let it not be missed that the Sea Harrier ski-jump take off was designed by a sergeant on the back of a fag packet.

[Cirrussy]

What can I say, other than I highly endorse his development technique!

[billslugg]

For simplicity, let's say it's a fairly fat passenger weighing two hundred pounds.

In the US, 74% of adults are overweight, the average male weighs 196 pounds, the average female 168. The world average for adults is 137.

Yes, we are fairly fat.

[BARKINGMAD]

"Yes, we are fairly fat".

Terribly non-PC, coming eastwards from the country which started the craze!

Aren't you supposed to say "gravitationally-challenged" so as not to offend those of a higher wake turbulence category?

'Twill soon be a hate crime over in EU to use such an abusive term in public or written communication, punishable by attending diversity training etc.

[Fareastdriver]

Years ago flying offshore from Aberdeen.

The so-called standard weight for the offshore passengers was 180 lbs.; 170lbs for him plus 10lbs. for his wet suit etc.. This oil company had a policy where they were weighed individually because that, in most cases as they weighed less, they could get more freight on.

I planned the trip and sent down the payload to traffic. They phoned up shortly after and asked if I could take some more to which I refused. Later on along came the manifest and I noticed that the passenger weight was an exact multiplication of 180lbs.

I went down to query this remarkable coincidence.

"They were too heavy when we weighed them so we reverted to standard weights."

[RAT 5]

How many dispatchers did you shoot?

[RAT 5]

Standard weights and consequential problems. I remember an incident years ago, on a small turbo-prop, I think. It was carrying a group of pax who had been to a coin collectors fare. They were stout gentlemen and had light overnight bags in the hold plus carry-on. The a/c performance was sluggish. Later it turned out that the carry-on contained their coin collection and was way over the 5kgs or whatever the standard allowance was. Each pax was a few kgs over the standard; multiply the whole lot by 30 pax and the overweight could be felt in the trim and overall performance.
I think they got away with it, or was there a crash? Some will remember better.

[Pugilistic Animus]

Rat5, Are you speaking of that accident in CLT?

[RAT 5]

Not sure: can't remember them all in detail.

[DaveReidUK]

Rat5, Are you speaking of that accident in CLT?

If you can be slightly more specific than "that accident in CLT", it should be relatively easy to establish whether the probable cause involved a loading discrepancy.

[Pugilistic Animus]

I forget the type but it was a small turboprop and the captain was female...the shifting weight due to gear retraction caused that airplane crashed into a hangar

[Rwy in Sight]

I think you are referring to https://aviation-safety.net/database/record.php?id=20030108-0 accident

[DaveReidUK]

I think you are referring to https://aviation-safety.net/database/record.php?id=20030108-0 accident

That was certainly at Charlotte, and did involve the aircraft hitting a hangar, but the probable cause was established as incorrect elevator rigging and a CofG substantially aft of the limit, causing an uncontrollable pitch-up.

So nothing to do with the landing gear (the MLG retracts forwards on the 1900, so retraction couldn't have contributed to the pitch-up).