Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Weight & Balance  
User currently offlineBrodieBrazil From Canada, joined Nov 2003, 88 posts, RR: 0
Posted (11 years 1 week 5 days 14 hours ago) and read 6298 times:

Preparing for my Private Pilot's license, I'm learning that weight and balance of both passengers and cargo are very important for small planes.

I'm wondering with the thousands of daily commercial flights, how important are things like balance and center of gravity on large heavy metal jets? Thanks!

Brodie

27 replies: All unread, showing first 25:
 
User currently offlineXFSUgimpLB41X From United States of America, joined Aug 2000, 4229 posts, RR: 37
Reply 1, posted (11 years 1 week 5 days 14 hours ago) and read 6227 times:

Very much so...we do it before each flight. It affects our trim settings, speeds, and is very very very crucial to safety.


Something to add to it, Brodie: Large jets have empty weight, fuel, passengers, and cargo just like small planes...except for us the flight crew is already figured into the basic weight of the plane. Also, we do our CG in percentages instead of in inches, but the principle is the same. We have tolerances within which the CG and weight must fall, just like the light planes.

Good luck on your private!

[Edited 2003-12-11 00:27:29]


Chicks dig winglets.
User currently offlineTeva From France, joined Jan 2001, 1875 posts, RR: 15
Reply 2, posted (11 years 1 week 5 days 14 hours ago) and read 6221 times:

They are extremely important as well, and if wt/bl is not done properly, or if the plane is not loaded as per the instructions, the result can be as serious as a crash.

However, when you have a bigger plane, you have more flexibility to balance it.
Teva



Ecoute les orgues, Elles jouent pour toi...C'est le requiem pour un con
User currently offlineWestJetYYZ From , joined Dec 1969, posts, RR:
Reply 3, posted (11 years 1 week 5 days 14 hours ago) and read 6222 times:

Hey Brodie, they are just as important on the big jets as the small ones. We prepare weight & balance for each flight just like you would in a small plane. Taking into account the same things, fuel on board, cargo/bags on board, passengers on board, all those things.

User currently offlineMSYtristar From , joined Dec 1969, posts, RR:
Reply 4, posted (11 years 1 week 5 days 13 hours ago) and read 6191 times:

I do weight and balance for Airbus 318/319's and 737-300's. Accuracy is a must. If you have one number wrong while doing your calculations, the whole thing will be messed up. Even large commercial airliners have specific weights (max takeoff/landing weights, zero fuel weights, etc) that cannot be exceeded...if they are, the plane cannot fly.

Weight and balance can get kind of stressful at times (usually only when last minute bags/passengers are added to the manifest, which can throw off your numbers), but it's pretty interesting to learn how the whole process works.

Any other questions regarding weight/balance, feel free to email me.


Stephen/New Orleans


User currently offlineCcrlR From United States of America, joined Aug 2001, 2242 posts, RR: 0
Reply 5, posted (11 years 1 week 5 days 13 hours ago) and read 6159 times:
Support Airliners.net - become a First Class Member!

It's important with maintenance too. You deal with adding, removing and relocating things, and with passengers. If there is too much weight in one area, the plane gets to be nose or tail heavy. Also the Center of Gravity changes with the weight and contents inside the aircraft. You have limits also with aircraft and you must be in those limits for the aircraft to be legal to fly. With passengers, we have a certain number we give any passenger that is going to fly since we don't know how much each passenger weighs. If you have any questions about this you can e mail me too.


"He was right, it is a screaming metal deathtrap!"-Cosmo (from the Fairly Oddparents)
User currently offlineBrodieBrazil From Canada, joined Nov 2003, 88 posts, RR: 0
Reply 6, posted (11 years 1 week 5 days 13 hours ago) and read 6132 times:

Hey Thanks guys for all the info. Very interesting and satisfying to know that so much thought goes in to every flight.

So is it done just like on small aircraft where (Weight X Arm = Moment)? Also, is the datum usually the nose cone?

Also, here's another question. Say it's a Southwest flight, with open seating... and say for some reason all the passengers wanted to sit either in the front/back or to one side left/right of the aircraft? Does the pilot(s) or flight crew try to do their own balancing?

Brodie


User currently offlineWestJetYYZ From , joined Dec 1969, posts, RR:
Reply 7, posted (11 years 1 week 5 days 12 hours ago) and read 6115 times:

Hey Brodie, I'm only familiar with the 737 (which we have at WestJet) because that is what I work with. We look at total weight forward and aft of the CoG. This is put into a computer, to produce a trim setting to balance out the aircraft.

Luckily, like with SouthWest, people are preety good about spreading out. What they do is that the flight attendants will count the zones (on our 737-700s at WestJet it is rows 1-7, 8-18, 19-24) and then the pilot can trim the aircraft to compensate. In the event that it is too much, and the plane is out of trim... then we can always move people around.


User currently offlineGoose From Canada, joined Aug 2003, 1840 posts, RR: 15
Reply 8, posted (11 years 1 week 5 days 11 hours ago) and read 6083 times:

WSYYZ,

I was told once upon a time that WS' load planning for every flight was done from the Ops Centre in YYC - and the trim sheets for the -700s were made there using a program and transmitted via the aircraft's ACARS system.

I heard that the -200s were still done from a local airport "ground support" office...... but that the actual "plan" of where things go comes from YYC, using the SABRE system or a derivative.



"Talk to me, Goose..."
User currently offlineDLMHT From United States of America, joined Oct 2003, 99 posts, RR: 0
Reply 9, posted (11 years 1 week 5 days 9 hours ago) and read 6027 times:

For DL, each flight, of course, has a dispatcher who will file the flight plan and determine the outbound fuel load. In addition to the dispatcher, there is a Load Control Center (LCC) in ATL that is responsible for compiling a Automated Weight and Balance Sheet (AWABS) for each flight and sending it to the corresponding staion.

In the station, there will be a load planner who is responible for planning out each flight (i.e. how many bags/mail/freight to put in each cargo bin). Upon departure, this person enters each bin weight into the copmputer as well as passenger counts and fuel weights, and then transmits the Final Weight Data Record (WDR) to the printer. Ths printout is given to the pilots, and it tells them what to set their stab trim at, and gives them takeoff speeds and weights for each corresponding runway.

Any last-minute changes can usually be tranmitted to the pilots via ACARS.

I'm not sure how this is handled at the other carriers, but is usually somewhere along these lines.

DLMHT


User currently offlineL-188 From United States of America, joined Jul 1999, 29832 posts, RR: 58
Reply 10, posted (11 years 1 week 4 days 15 hours ago) and read 5878 times:

Most Airline pilots don't do their weight and balance sheets. The dispatchers do that.

As far as bags, there is an assumed average per bag, I think they upped it recently. It used to be something like 35 lbs

So what happens is that you end up with a bag count for each cart in the bagwell, typically there will be more then one cart for a flight, each going to a different destination so it is simply a matter of telling the ramp crews what cart goes in what belly.

Likewise on freight, the weight is pretty well known, since you are paid generally by the pound moved. Those likewise are either loaded onto carts, or cans/igloos. The weight noted and again sent to load control or dispatch, who then does the math on where to load it onto the airplane.

The weight and balance as well as the fuel load is then handed to the pilot, who generally looks at it with a dumb look on their face and says.....hmmm ok!



OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
User currently offlineGoose From Canada, joined Aug 2003, 1840 posts, RR: 15
Reply 11, posted (11 years 1 week 4 days 13 hours ago) and read 5857 times:

Some companies have dedicated "Load PlanWeight & Balance" positions.

.... and Transport Canada's standard bag weight is 25 lbs/piece.



"Talk to me, Goose..."
User currently offlineRepaulson From United States of America, joined Oct 1999, 103 posts, RR: 0
Reply 12, posted (11 years 3 days 21 hours ago) and read 5756 times:

Another student pilot here... Do you guys assign an average weight for each person (+carry on)? I know most times when at the front desk our checked bags are weighed and I would imagine that data is collected and added to the W&B sheet somehow. Is this the case?

User currently offlineSlamclick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 13, posted (11 years 1 day 20 hours ago) and read 5706 times:

Repaulson:

The way it might work at an airline is something like this.

The load desk prepares the weight and balance for each departing flight. They actually use a computer program that solves all the math, and it is ready at the final keystroke. They get inputs from several sources.

The flight plan / dispatch release prepared for the flight tells them which aircraft is making the specific flight. Each plane has its own basic operating weight and moment. It also states how much fuel is required for the flight (burnoff to destination + alternate + reserves) and if it is desirable to tanker fuel through the destination or carry "extra" fuel. The maximum allowable takeoff weight is almost never the maximum certificated takeoff weight. It is almost always limited by performance or by landing weight at destination on short segments.

When the agent is ready to close the door they confirm the passenger count with the flight attendants, check it with the pilots and check the fuel load aboard with the pilots. After closeout, they input this information into the system and the final count and fuel load gets reported to the load desk.

The bag handlers close the cargo doors and report the bag count and into which pits before they move on to the next airplane. Bag count and distribution gets transmitted to the load desk. (probably straight into the computer program)

The airline's operations specialists at the departure airport (dispatch may be three time zones away from your departure point) confirm the weather and runway in use at departure point. Particularly barometric pressure and temperature must be such that the plane will perform as well as, or better than the pre-flight planning assumptions. If all is okay with winds and weather the weight and balance gets closed out and transmitted to the airplane. Domestically, it usually arrives by ACARS.

The pilots verify the runway in use, the temperature and baro, the passenger count, ACM's (jumpseaters) XFA's (extra flight attendants) live animals in the pit, HAZMAT aboard and maybe a couple of other things. They set up the cockpit for departure according to the data on the W&B message: Flap setting, stab trim, airspeed and engine power bugs. These things become takeoff briefing items.

All of this was done with an FAA-accepted "standardized" weight and balance program that makes a number of assumptions regarding bag and passenger weights by season, and passenger seating preferences. Any time a new gadget is added to the fleet, its weight and location are factored in to the BOW and moment for each plane in the fleet. It is very complex, but each element of it is pretty simple.

There have been incidents where no one sat in the first six rows or some such thing and the plane was difficult, but not impossible to control until they were re-seated. In other type of (non-airline) operations aicraft have been destroyed through seriously bad loading or by weight shifting during takeoff. (Maybe I'll tell that war story some day.)

All of this sounds like it would take a long time but it normally happens behind the scenes and in such a way that the W&B comes up during the pushback.




Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineRepaulson From United States of America, joined Oct 1999, 103 posts, RR: 0
Reply 14, posted (11 years 20 hours ago) and read 5643 times:

Thanks Slamclick! Very informative. A lot of action going on behind the scenes. In a prior life I worked at IAD loading bags for a few summers. I remember to load sheets for the heavies but for the DC9s and 737s we tried to even things out... Freight, cargo and bags. I just took my FAA ground exam and learned all about w&b, arms, moments and the such... Thanks again!

Repaulson


User currently offlineB747skipper From , joined Dec 1969, posts, RR:
Reply 15, posted (11 years 18 hours ago) and read 5640 times:

Obviously, weight and balance is important in any airplane...
xxx
In the 747 passenger airplane, we are actually only concerned about getting an idea of the weight of the aircraft... Outside of USA, everybody uses the metric system - a good number (and easy to use) is to assume 100 kg per passenger + baggage, so if we have 370 passengers = I put the number 37,000 kg as payload in my head for planning purpose. Actual numbers are generally very close to that number.
xxx
CG location is not that important in the passenger 747 - actually you could move all the people around in one or two forward or rear cabins - it would have very little effect as far as bringing the CG out of limits.
xxx
We are concerned about the CG however, for economy reasons, we try to load the airplane as to obtain about 28% MAC for CG, since it is better to have a rather "aft CG" for cruise fuel flow... a forward CG is detrimental to the cruise fuel flow...
xxx
Any cargo airplane - and 747 in particular, require an accurate computation, because it would be easy to get in troubles, overweight - or outside of CG limits - also excessive loading for the floor - some areas of the cabin are marked as to what maximum loading can be located there. Loadmasters often fly along on cargo airplanes to perform/oversee the loading/offloading of the airplane, and compute the weight and balance, etc...
xxx
Cargo airplanes such as the 747F often have a "weight and balance" computer taking pressure sensing from the gear (nose wheel and main gears) to get a reading of the aircraft weight and CG location... these systems are quite accurate when well maintained.
xxx
Happy contrails  Smile
(s) Skipper


User currently offlineCanadianNorth From Canada, joined Aug 2002, 3395 posts, RR: 9
Reply 16, posted (11 years 11 hours ago) and read 5604 times:

My dad used to do weight and balance for Canadi>n North back when they were part of Canadi>n Airlines. From what i understand it is very important.

Basically, put too much in the back the thing will be harder to control and possibly fall on the tail, too much forward and it will also be harder to control and could have problems with the roatation... So yeah it might be a good idea to have your weights balanced out wether your hopping across town in a cessna 172 or hopping across the pacific in a 747...



CanadianNorth



What could possibly go wrong?
User currently offlineYbacpa From United States of America, joined Feb 2001, 1108 posts, RR: 1
Reply 17, posted (10 years 12 months 4 days 20 hours ago) and read 5574 times:

Years ago I used to fly model airplanes. The balance was absolutely critical to making the model flyable. The particular model I used to fly by design had substantial flexibility in the exact mounting position of the batteries to compensate for different manufacturer's engines & electronics. One of the advantages of this was I was able to adjust the performance for different types of flying; for example if I needed to take off and land in a tight space I'd make the plane tail heavy, or if I wanted to be able to make tight turns in the air I'd make the plane topheavy.

Of course it was always a careful balancing act (no pun intended), and ultimately getting too aggressive with the handling led to one too many crashes, and my eventual departure from the hobby (oh, and I got my drivers license, so I had a new toy to spend my money on).



SkyTeam: The alliance for third rate airlines finally getting their act together!
User currently offlinePat From Belgium, joined Aug 2000, 110 posts, RR: 1
Reply 18, posted (10 years 11 months 3 weeks 3 days 13 hours ago) and read 5501 times:


Hi guys,


Speaking about weight and balance, has anyone any idea where I could find some information about the principles of aerodynamic - without going too far into details, formulas "Einstein style", etc ,... - and especially how does an aircraft fly (four forces drag, lift, etc, ... ) ???

In the same spirit is there any chance to find some info about loadcontrol / weigh and bal on the web somewhere ?

Tks for yr usual replies !


Pat


User currently offlineSlamclick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 19, posted (10 years 11 months 3 weeks 3 days 13 hours ago) and read 5499 times:

Pat

I believe that most up to date Private Pilot study guides would cover that stuff pretty well. And you really don't need to get Einsteinish about it. When you understand the statement "weight times arm equals moment" and a few of its implications you will know what you need to know.

I could give it to you in ten minutes on a marker board and you'd be ready to take on a 747 or a helicopter.

Don't really know whose study guides are the best at the moment. Check a couple out.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlinePat From Belgium, joined Aug 2000, 110 posts, RR: 1
Reply 20, posted (10 years 11 months 3 weeks 1 day 19 hours ago) and read 5454 times:


Hi Slamclick and thks for yr help.

Nevertheless, do you have any idea where I could find these kind of info on the web ? I am not preparing my private license yet and as such I have no book at disposal.

To Slamclick and all of you, if you have any idea about where to find some explanations about W&B and especially aerodynamic laws or how does an aicraft fly, just let me know !

Tks a million,


Pat


User currently offlineSlamclick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 21, posted (10 years 11 months 3 weeks 1 day 18 hours ago) and read 5425 times:

Pat

No, sorry I don't know of any on the web. Where I live, the public library has some volumes on the subject including fairly up-to-date private pilot study material. Local book stores have them for a couple of dollars. But I just don't know about where you live.

Browse around though. I would not be surprised if someone had built a website with this stuff on it.

Good luck



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineLeezyjet From United Kingdom, joined Oct 2001, 4042 posts, RR: 53
Reply 22, posted (10 years 11 months 2 weeks 4 days 12 hours ago) and read 5373 times:

I do flight dispatch in the UK.

We tend to do the weight and balance 3 differant ways in the UK but these differ according to airline. Also in the UK a Flight Dispatcher is NOT required to hold any type of license to dispatch aircraft or produce loadsheets so basically anybody can become one and just pass the airlines own training to dispatch flights !!!. Unlike the US where the Flight Dispatcher completes a course similar to the Flight Crew but without the flying part.

1. The Load Controller will plan the load and then produce the final loadsheet as well as running the turnround - so basically controls the whole flight. There is no backup with this system so if he/she makes a mistake there is only the flight crew who can pick it up - but if they don't know how the a/c is loaded then they might be unaware there is a mistake.

2. There will be a Central Load Planning (CLP) department that produces the load plan and final load sheet and a Flight Dispatcher will run the turnround at the a/c side. This way the flight dispatcher can check the loadsheet when it is recieved for any errors as he/she will know how the a/c is loaded so can check for mistakes. Sometimes the loadsheet will also go direct to the cockpit via ACARS. The flight dispatcher will liase with CLP incase there are any changes to the load plan.

3. The dispatcher will run the turnround but will tell the flight crew how the a/c is loaded and give them a copy of the passenger breakdown and the flight crew will prepare their own loadsheet - usually manually. Tends to be smaller airlines or low cost carriers.

Also most airlines within Europe have a central flight planning department usually based at the airlines HQ that produce all the flight plans then distribute them to each airport via SITA telex or e-mail. They also tend to have 1 central operations department that co-ordinates all the a/c movements for the whole network.

Sometimes the weight and balance can be a pain in the a$$. When I was at Bmi we used to send a 734 from LHR-MAN about 25mins after another flight had departed to MAN so it was always empty. The 734 is a real b!tch to get in trim with hardly any passengers or bags in the hold on a short sector.

Also the F100 cannot depart completely empty. It will not be in trim with no passengers and without anything in the holds so we always had to add about 250-300kgs of ballast into the holds to get it in trim.

You get to know with experiance how each a/c will trim best. A 735 is best with the weight in the front whereas a 733/734 is better with weight in the back. An A320 needs weight in the front as it is possible to tip it onto it's tail if all the weight is in the back - it's possible to do this on a 744 too - but not recommended !!.

Believe it or not the L10-11 is better with the weight in the back. This suprised me when I first dispatched them.

Some airlines will have a standard load for each a/c type - usually the charter airlines or low cost carriers that bulk load their a/c and just carry passengers and bags. It helps speed up the turnround as the loaders at each station will already know in advance how to load that a/c type without having to consult a load plan or speak to the Dispatcher.

Just a bit of info for you from the UK.

 Smile



"She Rolls, 45 knots, 90, 135, nose comes up to 20 degrees, she's airborne - She flies, Concorde Flies"
User currently offlineXXXX10 From United Kingdom, joined Jan 2000, 777 posts, RR: 0
Reply 23, posted (10 years 11 months 2 weeks 1 day 23 hours ago) and read 5311 times:

I would be interested to know what checks are done on the accuracy of the figures.

In the report for the Concorde crash it was said that the aircraft was nearly 600 kg overweight, there were apparantly many bags wheich were loaded onto the aircraft but were not on the loadshhet. How does a pilot know that this won't happen again.

I should mention that according to the report this extra weight did not have a major effect on the accident.


User currently offlineSlamclick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 24, posted (10 years 11 months 2 weeks 1 day 21 hours ago) and read 5304 times:

XXXX10

Not sure what error trapping is in place before the crew gets the final numbers. I would hope there is some layer of safety there. As for the pilots we've had the final boarding figures and we know our fuel load from the dispatch release, the fuel ticket and the gauges. It would be unlikely that we would spot an error in bags or cargo so long as that error fell withing the range of possible.

That said, mistakes do happen. I got a final weight and balance from a small-town station and the takeoff did not feel right. Up at cruise I took another look and they had shown the fuel burnoff to destination (8000 lbs.) as the fuel on board. They'd left off the fuel to alternate and reserve fuel. The fuel was actually on board and the dispatch release, fuel ticket and gauges all showed that we'd had 16000' lbs, not eight. The CG was not much affected since fuel tanks are near the CG anyway, but we were eight thousand pounds heavier than the W&B said, so the V-speeds were all low. We corrected VREF for landing ourselves and informed the station of their mistake.

I've heard of a couple thousand pounds of magazines or newspapers accidently left on the airplane but removed from the W&B. Errors can happen but these things are normally well within the capabilities of the planes to handle. Many airliners when properly loaded, will be near one end of the green band on the stabilizer trim range. The plane, in that configuration can be hand-flown without extraordinary effort, by the average pilot with the trim set at the full opposite end of the green band.

Concorde had bigger problems. You are correct in that it did not help them at all, but it played a tiny part in the whole event.





Happiness is not seeing another trite Ste. Maarten photo all week long.
25 XXXX10 : Thanks for your reply, this does sound worrying, I am surprised the FAA doesn't do the odd spot check and way an airliner either on departure or arriv
26 Jhooper : Also, is the datum usually the nose cone? The datum line could be anywhere. On my plane, it's the firewall. Anyway, in our private flying, we usually
27 Liamksa : Does anyone also compute the position of the C.G. with respect to the lateral axis? Can't say i ever have. Only time it really occurs to me is when se
Top Of Page
Forum Index

Reply To This Topic Weight & Balance
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
RJ Weight & Balance posted Sat Mar 6 2004 02:54:47 by Bruce
Weight & Balance posted Thu Dec 11 2003 00:14:46 by BrodieBrazil
Weight & Balance Certified posted Sun Jul 20 2003 06:59:22 by Bruce
Weight And Balance posted Thu Jun 16 2005 21:41:29 by Corsair2
Weight And Balance On LD-3 Capable Aircraft posted Thu Jan 20 2005 03:11:17 by Flybyguy
CRJ-440 Seating/Weight And Balance posted Tue Jun 22 2004 19:44:05 by BoingGoingGone
737-400 Weight And Balance? posted Thu Dec 18 2003 07:48:10 by USAFHummer
Incorrect Weight And Balance Data For GA Aircraft posted Fri Jul 4 2003 23:31:17 by Flyf15
Weight And Balance On Airbus posted Mon Jan 20 2003 01:26:06 by Pat
Corporate Jets Weight And Balance posted Tue Apr 2 2002 03:46:40 by NormalSpeed

Sponsor Message:
Printer friendly format