Hi all,

Maybe this is the wrong forum, but the full scale forum does not seems to have anyone checking in often at all.
Ok, i have been racking my brain, but can't seem to be able to find the answer. How do they load and stay balance
for any jumbo jetliner? I know they have a passengers manifest after checking in and the total checked in luggage
counts, but the total weight of passengers is a great variable. Since each and everyone is somewhat similar in weight
variance, but some and often many are much bigger than other. How do they loaded all that luggage, freight, and people
and stay balance on the CG? Oh also one last question. How do they know the total weight of the aircraft, after deducted the
total weight of the fuel, freights, and luggage? Again, people's weight is a great variance due to seating assignment,
and they can't really guess it. Does the aircraft has a scale built in the struts or something?

Sorry for the seems to be a dumb question guys.
Thanks gentlemen!

google it "How do they load and balance airliners"

i was wondering the other:how they balance after lunch when all get in line on the tail for the toilet?...maybe all crew waits in the cocpit for everybody to unload?lol

...but i guess c.g. in that sped doesnt matter[8D]

yf,

It's not really a dumb question because it's a pretty complicated process. Here's a short explanation:

The airlines use an average “summer weight� and “winter weight� for passengers which takes into account clothing and carry on luggage. They also have the option of using “child’s� weights for children. They know where everybody is sitting and/or they assume an average distribution when they calculate passenger weight cg. It’s negligible if a few people change seats or move around.

They weigh your luggage when you check in and they know the weight of any freight. They assign the luggage/freight to luggage “bins� and calculate it’s cg.

They add the passenger and freight weight/cg to the known Operational Empty Weight (OEW) and cg of the airplane to come up with a Zero Fuel Weight (ZFW) and cg. The only thing left to add is the fuel weight. They run calculations to be sure the overall cg stays within limits as the fuel is burned during flight.

They used to make us do these calculations manually but now it’s done mostly by computers.

It may seem a little imprecise, given all the variables, but the calculations are conservative and there is a pretty good margin for error.

Craig

Do you think they use different average weights depending on where they are? like an average for a flight in japan compared to on in the states?

Most modern airliners built since the 80s can measure the weight on each landing gear. If you can do that, you (or the flight computer) can calculate the CG location.

- I have been bumped from a flight before (on an old 727) that left with empty seats due to CG considerations.-

Well I do know they recently upped the "average" passenger weight for U.S. domestic flights at my airline. Not sure if they make international adjustments.

I'd imagine that Americans, unfortunately, are the "worst case scenario" and if the planning were done for our "here is your seatbelt extension" fat-*******s, then everything less than that is a piece of cake!

My god, some of these people have SUED for being charged twice, even though they occupied two seats ! [:@]


To expand on Craig's excellent explanation above (which covers larger aircraft), some smaller aircraft, because an individual can make more of a difference in percentage terms, actually BLOCK rows of seats forward or aft to keep the CG within range. If, for instance, there is a heavy luggage load in the back, then some aft seats may be blocked, and visa-versa.

I can't say that you are wrong, John, but I am unaware of any weight measuring landing gear and I'm perplexed that having made my living in a variety of old and new jets since 1985, I have never even heard of the concept, even though "most" airliners can do this...Can you expand on which a/c are so equipped? I'm always eager to learn.

Thx, Don.

The B777 has a pressure switch on the nose gear that measures the amount of weight applied to it.
This device is used to position the trim green band. In other words, it will tell you what CG range is available.
However it is not used to check the real aircraft weight since it is only done on the nose gear.

The DOW or Dry Operating Weight is base on figures available from the maintenance.
The plane is scaled after every C checks. A number of jacking devices are used to lift the plane and weight it.
The weight distribution on every jack is entered into a program that gives the basic weight and basic index. These figures are used to compute the DOW and DOI ( Dry Operating Weight and Dry Operating Index ).

Most European airlines use an average passenger weight to compute the loadsheet (JAR-OPS 1.620):
Male=85 kg
Female=70 kg
children= 38 kg
Infant= 10 kg
This weight includes the carry on luggage.
The check in luggage and cargo load is precisely weighted, and entered into the loadsheet program along with the cargo hold zone where it is going to be loaded.

If the job is done correctly, a loadsheet is precise within 1%.
On a 340 tons B777 this is still a 3,4 tons precision margin...

Hello all.

Thanks so much for the lesson. See, you learn new things every day.
Now i can say i finally knew how they load those giant aircraft with everything
and still stay balance. It's still mind boggling to see that heavy chunk of metal
roll down the runway and takes off every time. Look so effortless don't they.

Great Thread YF222000,

And thanks to the professional pilots on this forum for the answers.

I too am always amazed to see a large airliner take off. Watching 400 tons of aluminium, fuel and citizens accelerated to over 150 mph, and then be lifted into the air. When seen close up, it still looks like magic, even though I well understand the science.

(My wife thinks I’m a nerd when I go on about it)

Roger

Hi Roger,

Well, if we are nerds for the love of aircraft, then i guess she could call me a nerd too.
There's another amazing thing about it is watching a C-5 Galaxy loaded with an M1 Abram
taking off at Travis AFB. So huge, heavy crawling down the runway and then slowly climb
into the sky as if it will just stop in midair. I always love the sounds of those 4 giant engines
whines up for take off.

Hi All

Great explanations here.

I used to do manual weight and balance for a air carrier in the early 90's. We did a load plan before the flight with the known weights of the cargo and est. baggage weights. I tried to get the CG in the aft limit for better fuel burn, which I’m sure the ground crew did not like me for some days as we did re-arrange more than a few cargo pallets and baggage cans some nights.

The B-747-200 can carry a lot of stuff, of course the newer 400 is pretty impressive compared.

I wish I had a picture of the wheel computer that we used to calculate the balance it was a plastic wheel with a paper background that showed aircraft zones that you marked off moved the wheel, then arrived at the cg. Got pretty exciting some nights as the darn bag numbers changed right till departure and they wanted us to load the plane to the last Kilo. If i remember correctly the max takeoff weight for our birds was 371,945 KG which is 838,364.03 Lbs. Pretty crazy considering that at that weight you could loose one engine on takeoff (after V1) and still take off amazing....

Hey Duke,

Didn't know you were a former load planner. I flew 747 clasic freighters for a while with a routine max takeoff weitght around 830,000 lbs. Always trusted you guys to get it right and you always did!

Still amazes me these monsters ever made it off the ground.

Craig