Big Iron Weight and Balance

vheissu · January 22nd, 2007, 19:11

How do pilots of pax carrying aircraft calculate the weight and balance for any given flight? I was just curious because alot of factors depend on weight, and the weight is different for each flight. Thanks.

fish314 · January 22nd, 2007, 23:56

Quote:

Originally Posted by vheissu

How do pilots of pax carrying aircraft calculate the weight and balance for any given flight? I was just curious because alot of factors depend on weight, and the weight is different for each flight. Thanks.

Basically you use an approximation. 25lbs per bag, and 180 lbs. per person, or something like that. As long as your average is decent, it doesn't matter if one guy gets on board who is 400lbs. and another gets on who is 95lbs. and a 70lbs. little kid is sitting in one seat. It's all close enough for government work, if you are talking about big airplanes with lots of seats.

Of course, the smaller the airplane the more accurate you've got to be, because each person's weight is a bigger percentage of the overall weight of the airplane.

88MPH · January 23rd, 2007, 00:01

Quote:

Originally Posted by fish314

Basically you use an approximation. 25lbs per bag, and 180 lbs. per person, or something like that. As long as your average is decent, it doesn't matter if one guy gets on board who is 400lbs. and another gets on who is 95lbs. and a 70lbs. little kid is sitting in one seat. It's all close enough for government work, if you are talking about big airplanes with lots of seats.

Of course, the smaller the airplane the more accurate you've got to be, because each person's weight is a bigger percentage of the overall weight of the airplane.

Sounds like the deployment planes and their load planners. Litterly, it's like this.

X amount of troops @ 200#/body. X amount of rucks @ 90#/ruck.

Rucks go <here> and you, you, and you sit <here> <here> and <here>.

They don't care if all the bags weigh 40#, and if everyone is a beanpole.

ananoman · January 23rd, 2007, 02:52

Our plane isn't exactly 'big iron' as it can only carry 10,000lbs of gas and about 2,000lbs of stuff. It is impossible to load a Hawker out of balance, so if it is a part 91 leg, we just input the # of people and how many pounds of bags and gas into the FMS, which will figure out our weight and V speeds for us. For part 135 legs, we have a plotter that you use to draw lines on a weight and balance diagram.

woodreau · January 23rd, 2007, 11:12

Here's a linky for you - talks about weight and balance for 121/135 and 91K operators.

http://www.airweb.faa.gov/Regulatory...C?OpenDocument

You have to do a w&b even for airline passenger flights. I think most are automated, where I work we do it by hand, it takes a while when you first start out, but nowadays w&b is done in about 30 seconds. I spend more time worrying about whether I'm legal to dispatch and that the dispatcher hasn't hung me out to dry.

BobDDuck · January 23rd, 2007, 13:39

On the CRJ (for us anyways) everybody weights 189 pounds in the winter. Bags weigh 30 pounds with heavy bags weighing 60 and carry on bags weighing 20 pounds. There are three passenger zones that we use (A, B and C... duh). In the old days (before ACARS w&b) the captain would spin a wheel to ensure we were in compliance and to get a stab trim setting. No we just enter all the data and send it off and our numbers come back. Ironically enough I was flying a plane ALL day today that had the ACARS inop so I was doing paper weight and balance while the captain spun the wheel. Fun stuff.

A slight side note, and maybe somebody can explain this, but we did one leg with our cargo bin (in the back) max out with weight. It was the first time I flew a REALLY tail heavy plane and noticed that when we changed the wing camber with flaps there was a lot more pitched motion then normal. I'm trying to think logically and the only thing I can think of is that the weight in the back was moving the CG around more at different wing AOAs and was taking a while to stabilize. Anybody got a more aero eng. reason?

Doug Taylor · January 23rd, 2007, 13:45

Quote:

Originally Posted by vheissu

How do pilots of pax carrying aircraft calculate the weight and balance for any given flight? I was just curious because alot of factors depend on weight, and the weight is different for each flight. Thanks.

FAA "averages".

I think we use summer weights, winter weights and child weights.

Sullypilot717 · January 23rd, 2007, 17:34

Fish314 pretty much had it right on when he made reference to use of FAA averages when computing weight and balance for larger passenger jetliners (Boeings, Airbuses, MD's etc...). As a former ground agent for a major airline who did work at the gate, that is precisely what we was used when all the computations were put together! He's also right on when he said that those weights have to be more precise when one is dealing with smaller aircraft!

Of course, everything all centers around an airplane's center of gravity (or CG as we pilots call it), which is a central point where the entire weight of the aircraft is centered. Through testing by every manufacturer, a CG range is established for each type of aircraft produced. If, after all the computations are complete, the aircraft is outside of those limits, then there's the risk of structural failure to the aircraft itself (you know what that leads to next).

vheissu · January 31st, 2007, 14:10

Thanks alot for the great answers! All makes sense now

Derek_S · February 1st, 2007, 00:46

Quote:

Originally Posted by Doug Taylor

FAA "averages".

So does this mean I can just guesstimate on my ATP written and get away with it?

dbakeg00 · February 1st, 2007, 12:22

Quote:

Originally Posted by Derek_S

So does this mean I can just guesstimate on my ATP written and get away with it?

Yeah..what he said. Sometimes I feel like I just want to memorize those weight and balance answers so i dont have to tediously work out those problems.

Derek_S · February 2nd, 2007, 00:38

That's what my old flight instructor said he did, probably worked out a lot better than trying to do them; mess up one number and everything else is screwed.

Doug Taylor · February 2nd, 2007, 00:50

Quote:

Originally Posted by vheissu

How do pilots of pax carrying aircraft calculate the weight and balance for any given flight? I was just curious because alot of factors depend on weight, and the weight is different for each flight. Thanks.

At my airline, we don't do it. But we're given a printout called an "AWABS" (Aircraft Weight and Balance Sheet) with all of the details. Also we have a 'tolerance' so if the pax count is off, we don't have to print a new one.

Ask PeanuckleCRJ, he's going to be way sharper on AWABS than I am in a few weeks.

January 22nd, 2007, 19:11	#1
vheissu Junior Member Join Date: Aug 2006 Location: Henderson, NV Posts: 275	Big Iron Weight and Balance How do pilots of pax carrying aircraft calculate the weight and balance for any given flight? I was just curious because alot of factors depend on weight, and the weight is different for each flight. Thanks.

January 23rd, 2007, 02:52	#4
ananoman Senior Member Join Date: Dec 2002 Posts: 916	Re: Big Iron Weight and Balance Our plane isn't exactly 'big iron' as it can only carry 10,000lbs of gas and about 2,000lbs of stuff. It is impossible to load a Hawker out of balance, so if it is a part 91 leg, we just input the # of people and how many pounds of bags and gas into the FMS, which will figure out our weight and V speeds for us. For part 135 legs, we have a plotter that you use to draw lines on a weight and balance diagram. __________________ My observation is that those with an extreme knowledge deficit have a real hard time believing that anyone else knows something they don't. That's why the knowledge deficit never goes away. - tgrayson

January 23rd, 2007, 11:12	#5
woodreau Junior Member Join Date: Oct 2004 Posts: 269	Re: Big Iron Weight and Balance Here's a linky for you - talks about weight and balance for 121/135 and 91K operators. http://www.airweb.faa.gov/Regulatory...C?OpenDocument You have to do a w&b even for airline passenger flights. I think most are automated, where I work we do it by hand, it takes a while when you first start out, but nowadays w&b is done in about 30 seconds. I spend more time worrying about whether I'm legal to dispatch and that the dispatcher hasn't hung me out to dry. __________________ Good judgement comes from experience. Experience comes from surviving bad judgement.

January 23rd, 2007, 13:39	#6
BobDDuck Old Skool Join Date: Sep 2003 Location: Left Seat Posts: 5,736	Re: Big Iron Weight and Balance On the CRJ (for us anyways) everybody weights 189 pounds in the winter. Bags weigh 30 pounds with heavy bags weighing 60 and carry on bags weighing 20 pounds. There are three passenger zones that we use (A, B and C... duh). In the old days (before ACARS w&b) the captain would spin a wheel to ensure we were in compliance and to get a stab trim setting. No we just enter all the data and send it off and our numbers come back. Ironically enough I was flying a plane ALL day today that had the ACARS inop so I was doing paper weight and balance while the captain spun the wheel. Fun stuff. A slight side note, and maybe somebody can explain this, but we did one leg with our cargo bin (in the back) max out with weight. It was the first time I flew a REALLY tail heavy plane and noticed that when we changed the wing camber with flaps there was a lot more pitched motion then normal. I'm trying to think logically and the only thing I can think of is that the weight in the back was moving the CG around more at different wing AOAs and was taking a while to stabilize. Anybody got a more aero eng. reason? __________________ TBJC08 The Gear Monkey The Gear Monkey Store

January 23rd, 2007, 17:34	#8
Sullypilot717 Newbie Join Date: Sep 2006 Posts: 4	Re: Big Iron Weight and Balance Fish314 pretty much had it right on when he made reference to use of FAA averages when computing weight and balance for larger passenger jetliners (Boeings, Airbuses, MD's etc...). As a former ground agent for a major airline who did work at the gate, that is precisely what we was used when all the computations were put together! He's also right on when he said that those weights have to be more precise when one is dealing with smaller aircraft! Of course, everything all centers around an airplane's center of gravity (or CG as we pilots call it), which is a central point where the entire weight of the aircraft is centered. Through testing by every manufacturer, a CG range is established for each type of aircraft produced. If, after all the computations are complete, the aircraft is outside of those limits, then there's the risk of structural failure to the aircraft itself (you know what that leads to next). __________________ Take care and Happy Flying!!

January 31st, 2007, 14:10	#9
vheissu Junior Member Join Date: Aug 2006 Location: Henderson, NV Posts: 275	Re: Big Iron Weight and Balance Thanks alot for the great answers! All makes sense now

February 2nd, 2007, 00:38	#12
Derek_S Senior Member Join Date: Mar 2005 Location: Pleasanton, CA Posts: 398	Re: Big Iron Weight and Balance That's what my old flight instructor said he did, probably worked out a lot better than trying to do them; mess up one number and everything else is screwed. __________________ Ladies and gentleman, this is your captain speaking. Small problem, all four engines have stopped. We are doing our damnedest to get them going again. I trust you are not in too much distress.

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