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Weighting passengers saves fuel?

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Weighting passengers saves fuel?

Old 25th Mar 2012, 22:58
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Weighting passengers saves fuel?

For a long time we've been weighting passengers' baggage, but not actually themselves. Generally accepted 'weight' of a passenger is 75 kgs in summer period and 80 in winter. These are mean averages, derived from some kind of statistical research I guess. But inevitably actual weights of passengers are different (smaller). 75 and 80 kgs looks like very conservative figures. What if each passenger will be weighted at registration deck, thus actual weight of payload can be obtained and therefore fuel requirements for a flight can be calculated based on more precise input data (precise payload weight I mean). Also, %CG can be calculated more accurately, as well as takeoff speeds.

What is your opinion on this?
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Old 25th Mar 2012, 23:51
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75 and 80 kgs looks like very conservative figures
Clearly not an USA airline :-)

If anything those are a bit on the low side given the fast food culture in this country.

The other factor would be the significant extra time it would take to weigh/explain why to all the passengers.

I have heard of small commuter airlines moving people around to improve the cg, still has to be a bit disconcerting to be asked to move to front due to one's size.
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Old 26th Mar 2012, 00:07
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Would have to be done at the gate then, including hand luggage. But a good idea. More accurate would be some device in the struts that could display the exact weight and CG of the airplane.

Once I did a flight out of Bamako, MTOW on the loadsheet. On takeoff and during climb somthing felt very wrong. Well into the flight I went to the back and saw that the cabin was full of local males. Each one looked over 2 meters in height and 120 kilos at least. And their standard african carry on bedsheets, containing their belongings. Standard holiday weights were used, 75 kilos. As per contract, it was a charter.

As it was a long flight, we had plenty of time to study the burnoff tables. More or less 10.000 kilos above the loadsheet TOW. Using standard weights can be tricky.

Reloading the FMC with the newly calculated weight, the airplane felt normal again.

85 kilos does not sound conservative in many parts of the world but can be conservative in other parts, but using holiday weights is ludicrous. Who loses weight before going on a holiday or carries less hand luggage?
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Old 26th Mar 2012, 00:33
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Standard weights are always tricky. I understand that an airbus FBW aircraft can tell its pilots a pretty good aproximation of its weight once airborne. On our airbus fleet on a full aircraft apparently usually the aircraft think it weighs around 2 to 2.5ts more than calculated vial loadsheet figures. And we nearly never use charter weights anymore, instead split figures for business passengers of 88kgs, 70kgs, 35kgs and 0kgs for males, females, kids and infants. Holiday charter would be 83 and 69. However, flight crews are considered at 85kgs and cabin crews at 75kgs, both values are quite often wrong as well...

Airlines would weigh passengers if they could, and charge them for any extra weight. Alas political correctness stands against it.
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Old 26th Mar 2012, 06:01
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I have heard of small commuter airlines moving people around to improve the cg, still has to be a bit disconcerting to be asked to move to front due to one's size.
I've only seen that on low load flights and empty seats. Never seen them asking a PAX to swap with a heavier PAX.
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Old 26th Mar 2012, 06:38
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Body weight - Wikipedia, the free encyclopedia

Says average US male is 86kg, average female 75kg. A summer average of 75kg must assume some fraction are are children/empty/other nationalities.

PS: Add for clothes?
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Old 26th Mar 2012, 07:06
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Recall bad passenger weight estimation being a contributory factor in the following crash.

Air Midwest Flight 5481 - Wikipedia, the free encyclopedia

"Although the pilots had totaled up the take-off weight of the aircraft before the flight and determined it to be within limits, the plane was actually overloaded and out of balance, due to the use of incorrect, but Federal Aviation Administration (FAA)-approved, passenger weight estimates. When checked, the National Transportation Safety Board found that the estimates were over 20 pounds (9 kg) lighter than the actual weight of an average passenger. After checking the actual weight of baggage retrieved from the crash site, and passengers (based on information from next-of-kin and the medical examiner), it was found that the aircraft was actually 580 pounds (264 kg) above its maximum allowable take-off weight, with its center of gravity 5% to the rear of the allowable limit."

"As a result of the weight issues discovered, the FAA planned to investigate and potentially revise estimated weight values, something that had not been done since 1936. Air Midwest used an average weight of 200 pounds (90.7 kg) per passenger after the accident, but the NTSB suggests that airlines use actual weights instead of average. 70% of small air carriers still use average"

Last edited by Fostex; 26th Mar 2012 at 07:21.
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Old 26th Mar 2012, 08:33
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In my airline it would use extra fuel Since i,am certain
that the weights used are mostly incorrect.
76kg as an average for male/female in our case.

All our planes are 4 to 5% highconsumers, and after looking into all the variables it looks like paxweights estimates too low are the cause for this.

Using actual weight would of course not increase the actual burn ,but would increase the flightplan fuel since the basis then is a higher ZFW to start with.
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Old 26th Mar 2012, 08:51
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In 2009 EASA published a Europe wide passenger survey of passenger and baggage weights.

In the end they recommended a male weight of 94kg and female 75kg. Not sure if EASA intend to implement these findings at some point. The full report can be read here: http://www.easa.europa.eu/rulemaking...95%20Final.pdf
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Old 26th Mar 2012, 14:21
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The real question will be what are you going to do with all this information? The flight plan is prepared a couple hours before departure with the expected weights. The orders go out to the fuelers to put X fuel on plane Y at stand Z. The last thing we get from the ground staff is the load sheet. We compare the actual to the planned payload and as long as the actual is less, we're good to go.

So you weigh people as they check in and wouldn't have your payload till 30 minutes before departure. Then prepare the flight plan, get the paperwork to the crew and get the fueler to show up at the plane. At most large airports there is no where near a fueler per plane so you wait. About the only way to make it work would be to close the flight a couple hours before departure. For what? We figure it costs 5% of the tankered fuel to carry it. Say you have 300 kilos more than you need. That's 285 kilos you won't pump at the next station. We're talking about 5 gallons. Most fuelers squirt that much extra on all the time.
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Old 26th Mar 2012, 15:06
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I have a related question.

What is the point, other than adherence to rules, when a passenger turns up with a suitcase weighing 3 kilos over the allowance, of allowing them to transfer the 'offending' 3 kilos to hand baggage?

The overall load remains the same, but the extra weight (theoretically a few kilos per passenger multiplied by the number of passengers) of a tonne or so, is now in the overhead racks, meaning a higher CoG - not sure if that is relevant - and more space taken up, and more potential for injury if overhead lockers come open.
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Old 26th Mar 2012, 15:24
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The idea is correct but the implementation would be rather difficult. You also have to consider how much fuel you would actually save. On one hour flights in my aircraft you'd save approx. 12 kgs/1,000 kgs but as the passenger weights are a reasonable average, little would be saved but the cost of gathering the data would cost more than the fuel wasted. However, a one minute flight reduction saves 30 kgs. A pure idle descent saves about 150 kgs. A continuous climb saves even more. These are the areas where fuel savings can be made. Also, rather surprisingly, it's "environmental" and political restrictions that really piss away fuel. Pointless noise restrictions such as a minimum of seven mile finals when visual, SIDs which take you all round the houses, routings to avoid unused airspace because "telephone calls take up too much time" and the such like are the wasters of fuel.

However, you might be able to save some fuel by optimal CofG planning - only so long as you don't allow people to select their seats, which is what the full service airlines offer.

PM
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Old 26th Mar 2012, 17:29
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EU Ops standard weights for aircraft with more than 30 seats are 84kg or 76kg for holiday charters. That includes carry on baggage.

These weights are nonsense. But not a ridiculous as the figure given to us on return Hajj flights were we added 15% for good measure and were probably still a little under cooked!
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Old 26th Mar 2012, 17:38
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The other factor would be the significant extra time it would take to weigh/explain why to all the passengers
not so if the weighing plate for the ordinary lugagge is just a bit lower
 
Old 27th Mar 2012, 19:01
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Not an overload problem but as Master of a sidewheel paddle ship carrying more than seven hundred passengers I would regularly have to ask people to move to the uphill side of the ship to get both paddles in the water - made it much easier to steer .
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Old 27th Mar 2012, 23:35
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Our CAA requires a statistical analysis to be completed every five years. This is done by taking actual passengers and their carry on baggage and weighing them. Last time a sample of 10,000 pax on statistical diverse routes was used and the increase was up one kilo.

We also have different average weights for different sectors that have statistically higher or lower weights.
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Old 28th Mar 2012, 23:07
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@Tableview

that reminds me of my previous airline .. had a flight from OVD to ASW with the A320 , the commercial sold the flight based on maximum payload , RTOWs showed 2 Tons of extra load , instead of doing a fuel stop en route it was decided to move the luggage to the overhead pins so they don't show up in the Load sheet in case of a SAFA or local CAA check ... a middle eastern charter airline no names
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Old 29th Mar 2012, 22:23
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STAN

See #3
The Merchantman (VC9) - the converted Vanguard - has a device in the struts called STAN. I cannot remember what it stands for, but it gave a (very) rough total weight and c of g. IIRC it was asked its opinion when in a steady taxy. It saved my life once when all the pallet weights were completely wrong (the scales had iced up!).
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