Treeny From United Kingdom (England), joined Dec 2005, 317 posts, RR: 0 Posted (3 years 2 months 1 week 3 days 2 hours ago) and read 1469 times:
Hi All
After spending a lot of time over the last few years using MS Flight Sim I have started to understand now the concept of weight calculation of passenger airlines. For example data needed to calculate fuel quantities such as route length, alternate destination, ZFW, APU and taxi time etc etc.
However, I returned from Madrid with AR on Wednesday and I got to thinking about the process of how these calculations are made in the real world.
I started thinking about all this as I saw cargo and luggage being loaded up until the last minute on the plane and I wondered the process for the calculation of this data.
I also started wondering things like how does dispatch and the crew take into consideration hand luggage weight if at check in they dont weigh it - I mean does the dispatch use a weight per passenger average to calculate the ZFW and at what point do they agree on the final figure?
I guess luggage checked has its wight registered so a total luggage weight can be submitted but what about silly things like food cart weights, water to flush the loos and as I say individual passenger weight with hand luggage etc etc
I guess the key here is how do an airline calculate weights and at what point can they say - "This is our ZFW" today?
I hope this question is both clear and possible something you can all contribute to answer my questions.
Flyer732 From Australia, joined Nov 1999, 1207 posts, RR: 39 Reply 1, posted (3 years 2 months 1 week 2 days 22 hours ago) and read 1417 times:
I can't speak for all airlines, but at my company the checked bags are weighed at check in, so we get an actual cargo weight. For the carry on bags, we use an average of 20 lbs for every passenger, along with an average body weight. ( 190 lbs for an adult in the summer and 195 lbs for an adult in the winter)
The best is when we fly military, because we get actual bag and body weights including carry on bags. So we get an EXACT final payload.
ADXMatt From United States, joined Jul 2006, 796 posts, RR: 2 Reply 2, posted (3 years 2 months 1 week 2 days 21 hours ago) and read 1387 times:
Flyer 732 has it right.
For "special" charters (i.e. Military, football teams etc.) We get actual pax weights and bag weights.
For routine ops we have a standard passenger weight that includes carry on. (summer/winter are different weights) Bags that are checked they are divided into regular 30lbs or heavy 50lbs. Cargo is a known actual weight. Should a "carry on" get "gate" checked and put in the cargo hold it is counted just like the checked bags.
We use a 1/2 weight if there are small children onboard.
every so often we do a trial (a random selection of flights) for the FAA and use actual weights for bags and pax to prove that the standard weights used is acurate.
In the past few years the standard weights have gone up as we americans keep getting fatter.
The rest is all known.... i.e. fuel, empty weight etc. We do make adjustments for items removed from the a/c mostly catering carts should the a/c depart without any or some. As you know each cart weighs as much if not more then a pax.
HPLASOps From , joined Dec 1969, posts, RR: Reply 4, posted (3 years 2 months 1 week 2 days 20 hours ago) and read 1375 times:
Quoting Treeny (Thread starter): but what about silly things like food cart weights, water to flush the loos and as I say individual passenger weight with hand luggage etc etc
Things that are variable from flight to flight such as pax counts, luggage, and cargo are what need to be factored into the trim. Anything else, like catering carts, lavratory weights, etc fall into the weight knows as Operational Empty Weight (OEW). It is the weight of the aircraft minus pax, cargo, and fuel. Dispatchers should know what the OEW is all for all aircraft, and it might vary slightly from aircraft to aircraft within the same type of aircraft. This could be if any particular service item has been removed or added. For example, one of HP's 737s has air condition vents to the window side of the overhead compartments, a straight line down the edge of the aircraft instead of overhead vents. This might change the OEW a few pounds vs. a similar aircraft.
Fuel, cargo and pax are then added on to determine GTOW (gross take off weight) and of course, it has to be lower than the D/X's prescribed MTOW (Max take-off weight). There is an estimated taxi burn and trip burn calculated for the fuel and, in theory, should put you under the limites for the D/X's prescribed MLW (max landing weight). This is why planes that need to divert very shortly after take-off will circle for awhile - to burn off enough fuel to get under the MLW.
Flyer732 From Australia, joined Nov 1999, 1207 posts, RR: 39 Reply 5, posted (3 years 2 months 1 week 2 days 20 hours ago) and read 1354 times:
Here's a run down (as a loadmaster for lack of a better term)
I'm given a sheet that has the OEW of the aircraft, on that sheet it shows the ZFW and the MZFW.
I then find out how many passengers I have, and figure their weight if it is a normal flight, or get their weight if it is a special charter. Then get the baggage weight. I'll run basic numbers to find the best location to load the bags for the optimum CG. If it is a commercial charter, I go by % of seats per zone on the aircraft, if it is a military or special charter I dictate where the passengers sit, and I can better my CG by doing so. I find its more of a challenge on a light load, you have more room to play with and more room for error. A heavy load, there isn't much you can do, and the CG will most likely be right down the middle or close to it.
Treeny From United Kingdom (England), joined Dec 2005, 317 posts, RR: 0 Reply 6, posted (3 years 2 months 1 week 2 days 16 hours ago) and read 1294 times:
Guys
Thanks a million for the clear and concise answers.
My last question - as a rough average at what point ( this refers to time of departure) would a pilot input the weights into the FMC to get important data such as the v1, v2 and rotate speeds?
Is this usually done as a last minute thing or would this be able to be done with a lot of time to spare?
Thanks a million for the clear and concise answers.
My last question - as a rough average at what point ( this refers to time of departure) would a pilot input the weights into the FMC to get important data such as the v1, v2 and rotate speeds?
Is this usually done as a last minute thing or would this be able to be done with a lot of time to spare?
Cheers
Mark
At DL this is usually done once fuelling is completed. That is when the final WDR is produced and printed.
Position and hold runway one three right landing traffic on runway two two left
Goldenshield From United States, joined Jan 2001, 4052 posts, RR: 13 Reply 8, posted (3 years 2 months 1 week 2 days 4 hours ago) and read 1168 times:
Quoting HPLASOps (Reply 4): Anything else, like catering carts, lavratory weights, etc fall into the weight knows as Operational Empty Weight (OEW). It is the weight of the aircraft minus pax, cargo, and fuel. Dispatchers should know what the OEW is all for all aircraft, and it might vary slightly from aircraft to aircraft within the same type of aircraft.
We don't need to know them by heart. That's a near impossible job with a large fleet of aircraft. However, we do need to know where to find it, and in this day of computers, they are built into the computer systems, and modified by maintainance as needed.
"I heard that there are rumors on the internets" -- G. W. Bush at the second 2004 debate
ADXMatt From United States, joined Jul 2006, 796 posts, RR: 2 Reply 9, posted (3 years 2 months 1 week 1 day 22 hours ago) and read 1136 times:
Quoting Treeny (Reply 6): My last question - as a rough average at what point ( this refers to time of departure) would a pilot input the weights into the FMC to get important data such as the v1, v2 and rotate speeds?
At CO those speeds are on the Pilot Weight Manifest (weight and balance) at a previous carrier they had "flip cards" kind of like flash cards that they could flip onen the the page with there t/o weight on it.
3201 From United States, joined Oct 2004, 833 posts, RR: 1 Reply 10, posted (3 years 2 months 1 week 1 day 17 hours ago) and read 1107 times:
Keep in mind that the OEW isn't always constant for an individual aircraft -- since it includes things like catering and duty-free, it can vary by route or even for two flights on the same route at different times of day.
Also at least one airline I know uses an avg. OEW for all aircraft within an individual fleet. But most use actual weights for each individual aircraft.
Also I know at least one airline that uses historic data for the average passenger/baggage weight for each individual flight they fly, rather than just summer/winter weights. Many others don't go that far but do adjust for specific destinations (e.g. ski resort airports).
Quoting Goldenshield (Reply 8):
We don't need to know them by heart. That's a near impossible job with a large fleet of aircraft. However, we do need to know where to find it, and in this day of computers, they are built into the computer systems, and modified by maintainance as needed.
But really you don't even need to "find" them at all, right? They should be just automatically applied to all calcs in modern systems.
Speedracer1407 From United States, joined Dec 2004, 326 posts, RR: 0 Reply 11, posted (3 years 2 months 1 week 1 day 14 hours ago) and read 1090 times:
Quoting Flyer732 (Reply 1): 190 lbs for an adult in the summer and 195 lbs for an adult in the winter)
190 lb per person?! I'm under the impresson that the U.S. is the fattest country, and I'd be surprised if the "average" was 190. Your flag suggests non-US operations, but I'd be surprised if any country near the Eastern Europe/Western Asia area surpasses America in Fatness.
Do airlines assume passenger weights optimistically, or am I just out of touch writh regards to the average human weight.
FredT From United Kingdom, joined Feb 2002, 2101 posts, RR: 30 Reply 12, posted (3 years 2 months 1 week 1 day 14 hours ago) and read 1088 times:
The average weights are including clothes, carry-ons etc. Check FAA AC120-27E. It is one of the most readable FAA documents out there, and answers almost every question you can think of on passenger weight considerations.
With a no carry-on policy, you are allowed to deduce 6 lbs off those weights.
Rgds,
/Fred
[Edited 2006-09-24 10:32:18]
I thought I was doing good trying to avoid those airport hotels... and look at me now.
Goldenshield From United States, joined Jan 2001, 4052 posts, RR: 13 Reply 13, posted (3 years 2 months 1 week 1 day 12 hours ago) and read 1072 times:
Quoting 3201 (Reply 10): But really you don't even need to "find" them at all, right? They should be just automatically applied to all calcs in modern systems.
Re-read what you quoted. Specifically, the second half of the second sentence.
If needed, I can verify the correct numbers with maintenance's paperwork if the numbers in computer (and therefore, the release) do not match what the crews have on their cans; i.e., a mechanic failed to input the new numbers.
"I heard that there are rumors on the internets" -- G. W. Bush at the second 2004 debate
TristarSteve From Sweden, joined Nov 2005, 2816 posts, RR: 23 Reply 14, posted (3 years 2 months 1 week 1 day 11 hours ago) and read 1065 times:
Aircraft are weighed every 3 or 4 years. The fuel is drained completely, the lavs and water is serviced to normal, the loose catering is removed and the plane goes on the scales. This is compared to the last weighing to make sure it makes sense. The weight goes up over the years as dirt and dust accumulate and skin patches are fitted.
Until last year we had an individual weight for each aircraft, it is on a sheet stuck behind the cockpit door, but now we use a standard weight for the shorthaul fleets.
About 30 mins prior to departure the dispatcher produces a provisional load sheet which is given to the crew and signed for. After the doors are closed a final loadsheet is produced and sent by ACARS to the flight deck.
This allows the crew to input figures to the FMS in peace, and gives the dispatcher a few minutes to produce the final loadsheet when the last pax have boarded. When you have to produce a manual loadsheet there is always a rush from last pax accepted to loadsheet produced and then door shut.
It also helps when the dispatcher is not at the aircraft, they can be sitting in head office.
Modesto2 From United States, joined Jul 2000, 2413 posts, RR: 7 Reply 15, posted (3 years 2 months 1 week 1 day 9 hours ago) and read 1054 times:
Quoting Treeny (Reply 6): as a rough average at what point ( this refers to time of departure) would a pilot input the weights into the FMC to get important data such as the v1, v2 and rotate speeds?
At my airline, the last numbers we get are the bag count and the passenger count. Once I input that information into the ACARS weight and balance, it produces the TOW. At that point, the captain has the TOW and references the speed cards in input V1, VR, V2, VFS.
Goldenshield From United States, joined Jan 2001, 4052 posts, RR: 13 Reply 16, posted (3 years 2 months 1 week 1 day 7 hours ago) and read 1046 times:
Quoting TristarSteve (Reply 14): It also helps when the dispatcher is not at the aircraft, they can be sitting in head office.
We call those 'loadmasters' here in the states, and the majority of aircraft dispatchers in the states are located at the company's head office and don't see an actual plane all day (sans the ones out the window.)
"I heard that there are rumors on the internets" -- G. W. Bush at the second 2004 debate
Flyer732 From Australia, joined Nov 1999, 1207 posts, RR: 39 Reply 17, posted (3 years 2 months 4 days 19 hours ago) and read 953 times:
Quoting Speedracer1407 (Reply 11): 190 lb per person?! I'm under the impresson that the U.S. is the fattest country, and I'd be surprised if the "average" was 190. Your flag suggests non-US operations, but I'd be surprised if any country near the Eastern Europe/Western Asia area surpasses America in Fatness.
That 190 lbs will go for a 12 yearold who actually weighs less than 100 lbs, as well as the 260 lb 45 year old guy. So it "evens out" in the end. Thus its an average weight.
But as I said, I'm much happier doing actual weights, SO much easier.
And I work for a US carrier, but not always in the US.
411A From United States, joined Nov 2001, 1594 posts, RR: 9 Reply 18, posted (3 years 2 months 4 days 16 hours ago) and read 933 times:
Never mind the USA being the heaviest...not by a long shot.
Hajj flights returning from JED, with my carrier, assess pax weight at 230 pounds (105kg) which includes the ZamZam water these folks carry, which is now limited in the cabin to 3 gallons...more below.
And then there are the household ah...appliances carried in the lower holds, which include televisions, small refrigerators, cookers...you name it, they pack it, yes including kitchen sinks (usually stainless steel).
VERY often, extra freighters are chartered to carry the excess, which can approach 15 tons extra per normal pax flight.
Rather big business, coming up shortly.
DashTrash From United States, joined Aug 2006, 452 posts, RR: 2 Reply 19, posted (3 years 2 months 4 days 14 hours ago) and read 918 times:
My airline uses 184 lbs for the summer months, and 189 for the winter. Child weights are 76/79. A checked bag is assumed to weigh 30 lbs unless it's a "heavy" bag, then it counts as 2 checked bags (60 lbs). Planeside checked bags weigh 20 lbs.
We get our load manifest after the last bag is loaded, then add up the weights, calculate the CG and throw the paperwork out the door.
We use flip cards for speeds. When you have a heavy airplane, I've noticed large differences between what the speed card lists for Vref and what the ADC driven speed bug shows in the aircraft. No, the system isn't perfect, but it must be right since the FAA approved it....
Sponsor Message: 
.gif){kind=small}
From United Kingdom (England), joined Dec 2005, 317 posts, 
From Australia, joined Nov 1999, 1207 posts, 
From United States, joined Jul 2006, 796 posts, 
From , joined Dec 1969, posts, 
From United Kingdom, joined Feb 2002, 2101 posts, 
From Sweden, joined Nov 2005, 2816 posts, 
Sponsor Message: 
Printer friendly format
