Weight and balance?

[GCI35]

pd2/Bunnygirl.

Bunnygirl.
As an ex-BA Dispatcher I'm well versed on the vagaries of the 737/400. A two class config with more Club class than economy, eg to JER coupled with little deadload and a RLDW inevitably meant ballast on standby. One way of overcoming this problem early was to extend the Club class seating leaving enough seats in the rear cabin for economy pax, but ballast was used quite frequently. Some IT carriers crammed up to 180 pax on their aircraft, 28" pitch, can you imagine it?

pd2.
You mention being asked to move from an overwing seat "on a 400+ tonnes aircraft." Incredible. Or did you mean a 140 tonnes? Ryanair 737/800s have the first 6 rows blocked when the load is light, so my son tells me, I've never flown with them. Whatever the reason you were asked to move you should have complied. On larger aircraft like the 747 with a high fuel load the tendency is for it to be nose heavy with as much as 9 degrees nose up on the trim, the c of g in flight moves aft as the centre tank fuel is burned off. Shorthaul flights are a different kettle of fish, if the only way to trim the aircraft is to move passengers that's the way it has to be. Moving your 80 kilos from overwing, ( no change in balance ) to a seat further aft, a positive movement may have been all that was required to trim the aircraft.

[Peter Fanelli]

About me... ATPL Captain, with 18years experience working in Helicopter Offshore operations... so, yes, I understand the legalities of W&B, Manifests and the complexities of CofG calculations... which is why I find it so difficult to accept any of your explanations as... and I will say it again... I was overwing and asked to move three rows. So I doubt this was a request from the flight deck as moving one person 3 metres would have achieved next to nothing.

Then stop being such a richardhead. Of course the actual effect on the airframe of moving you is minimal, but you should be able to figure out that the paperwork has to show a correct load plan within the limits prior to departure. The reason you have to actually move on the aircraft is so that if the aircraft crashes they don't find your smouldering corpse strapped into a seat which would have put the CofG outside the limits.

And by the way, you might have been sitting over the wings at the wing root, but those wings are swept, good chance the CofG is aft of the wing root. It's not as simple as your helicopter where the CofG is going to be pretty close to right under the jesus nut.

About me...
Loadplanner...
Certified by
ProAir B737-300/-400
Air Aruba DC-9 MD80 MD90
Air Jamaica A320, A321, MD83
World Airways DC-10, MD11
Frontier B737-200/-300 A318 A319
Ghana Airways DC-10
Aer Lingus A330-200/-300
Mexicana A320
Kittyhawk B727F B737F

ATPL x 2 Australia and USA

Still want to wave yer willy?

[CanAmdelta1]

Yep,

#1
Not an unusual request prior to T/O on major commercial airlines with light pax load. I do as they request, then usually have them come back after wheels up and tell me to sit where I wish given the light pax load.

#2
When "Im" drivin' the plane, we always do what I want/ask.

Anyway on the lighter side....always, always obey a "position and hold" or in your case, a "re-position and sit" order when around aircraft and aerodomes...lol

[bunnygirl]

GCI35 and Peter, thank you for your explanations, as you can see pd2 you can probably tell that there are valid reasons for moving customers after they have boarded!

On my particular flight from Luxembourg, Mr "I know more than you" made his dissatisfaction known to all of us, for virtually the entire 50 minute flight! When I introduced him to the Captain on disembarking, explaining to the Captain that this was the Gentleman who was questioning his competency as a pilot (after all we were following his lawful commands), he suddenly turned from a captain of industry (that's what he told me anyway) into a red faced, bumbling school boy who couldn't get off the aircraft quick enough!

For reference, as well as the Rotterdam 737 incident. I seem to recall an Excalibur A 320 from LGW to MAN had a similar incident on take off back in 1992/3, due to incorrect loading ( yes I go back that far!). Am sure you ll be relieved pd2 that lessons are always learnt from incidences, hence the request to move seats! As a passenger on one of your flights, I wouldn't dream of questioning a lawful request that you or a colleague asked of me!

[Slickster]

I believe the C of G changes once airborne, to the centre of lift, so where you were sitting is irrelevant, with regards "I'm over the wing - it makes no difference". Everything is promulgated on the worst thing happening, and if I get an engine failure on take off, those three seats might make all the difference to me struggling to control the aircraft.

Juan Togoh is correct, in that weight and balance are critical in all stages of flight. But, I daresay, if all passengers ran to the back of the aircraft during flight, we might have the chance to do something about it. We do not have that luxury at take off, or landing, which is why passengers are required to move back to their allocated seats during such phases.

As this is is a CC crew Forum, I'll give you my short shrift answer. You readily admit that if the captain had told to move you had have, but considered it "idiotic" from the CC. Well, anything coming from the CC comes from the captain, by delegation, so just do what you're told, as indeed I would if I was on your helicopter.

[j_davey]

davecfm56... Thanks for the explanation. Not sure what aircraft you fly, but on the 737, it is actually quite difficult to throw the aircraft out of balance unless you decide to seat 350 passengers in the back 15 rows, or the load controller decides to load all the freight at one end of the aircraft.

Easier than you might think....

[Phil Rigg]

This thread is fascinating.

pd2 wanted to know why he was asked to move given his correct estimation of the virtually insignificant effect of moving his mass such a short distance on the overall weight and balance moment arm for the aircraft.

What he (and I in response to his asking the question) are looking for is why precisely did the CC member ask him to move an insignificantly short distance in an aparently ad-hoc manner? The reason stated was for "weight and balance" which to any reasonably educated pilot/engineer is clearly not the real issue. We are thus looking to hear a clear explanation of the real reason(s) why a CC member might make such a request including why they should choose to make up lies if the real reason is it makes cleaning the aircraft easier, etc. and in which case who in mangement has trained them to deliver such lies.

Instead of receiving the true and honest answers that we are looking forward pd2 has triggered an incredible series of responses, even one from the CC moderator whose response was "given anything to do with flight safety you do as I say even though I have absolutely no idea why I'm asking it" (even though if the passenger had been moved off the aircraft as suggested the CC member would have taken personal repsonsibility for making a far more significant change to the moment arm than their original request!), none of which have really answered his or her question to the full.

I am a GA pilot responsible for absolutely everything to do with the safety of any flight I make. No ops, loading or any other department just little ole me where the bucks stops.

Along with all other aspects, I have to calculate the weight and balance for every flight I make based on the actual weight of each pasenger and the seat I assign them to including the fuel load, dependent upon which tanks I load it, and the baggage load in the front or rear compartments.

The fact is that the weight and balance envelope is absolutely important in all phases of the flight and doesn't magically become insignificant after take-off. That is clearly some kind of old wives' tale that has been propagated among unknowing CC for some historically incorrect reason. I suspect it may be related to the normal process in most aircraft that the natural fuel burn-off during flight usually, but not always, makes the W & B envelope progressively easier to meet as the flight approaches landing.

As various posters have stated correctly, accidents have occurred in all phases of flight due to incorrect loading at any time including due to miscalculations during the fuel weight burn-off by the responsible person.

So to repeat the question to cabin crew. Knowing that you have no knowledge of the method of calculation or responsiblility for the W & B loading of an aircraft what are the various reasons (with an understanding of them or not) that you would ask a passenger to move a short distance and for each reason who exactly has instructed you to make this request and for what reason, true or false, did they give you for delivering the request?

pd2 and I would be fascinated to hear.......

P.S. I also find it unbelievable that with the majority of airlines assigning passengers to specific seats during check-in that it appears to be beyond the wit of man to build the W & B calculations into the seat assignment software!!

[john_tullamarine]

the natural fuel burn-off during flight usually, but not always, makes the W & B envelope progressively easier to meet as the flight approaches landing.


While noting your caveat, the underlying generalisation doesn't generally follow.

Usual practice is to check correct loading at TOW (or ramp weight) and ZFW. These two points usually cover most bases.

However, it is quite possible for some aircraft to start inside the envelope at TOW, move outside the envelope during flight, and then come back inside towards ZFW (or LW). There is no a priori reason why loading gets easier (or harder) as the fuel burns down.

I also find it unbelievable that with the majority of airlines assigning passengers to specific seats during check-in that it appears to be beyond the wit of man to build the W & B calculations into the seat assignment software!!

Not the case. Most systems will be driven by the desire to achieve the optimum cruise CG. While this often creates some interesting difficulties for light loads, the aircraft configuration normally will be associated with the operator's mean loads.

[Phil Rigg]

JT I agree with your TOW and ZFW comments. This simplifies the matter to the point it doesn't even need a calculation but just a reference table look-up which is safer as it avoids the human fallibility of making 'calculation errors'.

Note I did say "usually, but not always," to cover all eventualities. I was also just postulating the general trend as a possible explanation of the "W & B unimportant after departure" myth rather than trying to be precisely correct.

Thanks for the comments on seat assignments. That makes complete sense.

It would still be good to hear from CC the full list of reasons in their experience why they are asked to move passengers?

Clearly with all aspects of preparing an aircraft to depart its W & B is a very dynamic issue. All the more to ask why if moving one passenger three rows or even frog marching them off the flight at the last minute, as the mod suggested, are all that relevant? Given the lack of precision in the W & B calculation moving one passenger could inadvertently cause a marginal reduction in envelope margin rather than the desired improvement.

The truth of the matter is that a full and precise W & B calculation check should be done after each change in load including knowing exact weights and loading datum arms of all cargo, passengers, fuel loading, etc. but seeing as this is so impractical it is never done this precisely.

[john_tullamarine]

Clearly with all aspects of preparing an aircraft to depart its W & B is a very dynamic issue.

Hence, there is a need to use reasonably flexible loading systems so that the folk at the coal face can incorporate the weight control aspects into the main job of getting people and freight onto the aircraft and the aircraft away on time

... are all that relevant?

.. comes down to the need to put a line in the sand somewhere as to what level of accuracy is pertinent and important

Given the lack of precision in the W & B calculation

The calculations, per se, ought to be quite "accurate" as they involve only rudimentary arithmetic with little importance from round off and like errors.

However, given the sideline accuracies (errors) in things, such as,

(a) empty weight and CG data - there is little point in running the sums to ten decimal points worth of kg and mm if the starting point is, say, only accurate to 10-100 kg and 5-20 mm, depending on the aircraft size. Having done a lot of work on weighing errors, my view is that anyone who suggests that the empty weight (and, hence, the final calculated value) is accurate to the kg and mm is not aware of the realities of weighing and weighing equipment.

(b) standard weights - providing that the passenger load is moderate and the passenger population reasonably approximates the statistical basis for the standard weights, the use of standard weights is reasonable. Otherwise, all bets are off.

(c) use of loading zones - if each loading station is calculated separately, then the final errors are constrained and managed easily. With loading zones (a practical necessity for larger aircraft) it is quite easy to exacerbate loading problems unless there be prescriptive procedural requirements (and this, I suggest, is a typical reason for the CC's requests to passengers regarding reseating)

and the significant adverse consequences of serious misloading, one needs to be a little cautious in how one approaches the general loading problem.

.. moving one passenger could inadvertently cause a marginal reduction in envelope margin rather than the desired improvement.

.. probably not a concern of sufficient import to cause one to loose any sleep

a full and precise W & B calculation check should be done after each change in load including knowing exact weights and loading datum arms of all cargo, passengers, fuel loading, etc.

No problem doing that. However, the statement is not entirely correct or necessary. More importantly, the loading change infers that the previous calculation is now in error to some additional extent and that error needs to be looked at. There is a variety of techniques to do that - only one of which involves a complete recalculation of the original loading system.

[Peter Fanelli]

Phil,
It really is all about the paperwork. As you have said, moving one person a few rows is not really going to make a lot of difference to the actual operation of the aircraft in the case where there's one hundred or four hundred passengers or so.
However, the original poster did not mention which airline he was traveling on so I have no idea of the load planning system used in that case.
Weight and balance systems are required to be certified by the authorities, this can make it very expensive to set up computerized systems for smaller carriers. In a previous post of mine in this thread I listed nine airlines with which I have personal experience as a load planner.
Every one of them had a different system.
Two of them used Microsoft Excel spreadsheets, those being ProAir and Kittyhawk. In the case of ProAir they did not have assigned seating, the aircraft cabin was divided into zones. After the doors were closed the flight attendants would carry out a head count for each zone, pass this to the cockpit crew and they would give me those numbers by radio. I would then plug in those numbers into the spreadsheet along with the numbers of bags loaded fore and aft, also called in by radio to me by the ramp staff. When all was plugged in the spreadsheet would give me a bunch of numbers such as ramp weight, take off weight and most importantly the stabilizer trim setting. There were six numbers in all if I remember correctly but I don't remember them all.
I would then call these numbers to the cockpit crew and if all was hunky dory they would do what they need to do with them and be on their merry way.
BUT
Sometimes the passenger load would be bad or the bag counts would be bad and it would lead to the aircraft being out of trim, in these cases the spreadsheet would not give any numbers, just blank boxes. I would have to fix it by adjusting the passenger zone numbers until the spreadsheet was happy and presented me with final numbers. Passengers were moved because it would take too long to move bags. Once I adjusted the load and had numbers I would call the crew and tell them to move X numbers of passengers from zone B to zone C or something like that, then I could give the crew their numbers. Obviously the further you can move the passengers the fewer passengers you have to move.
Now here's the thing......They could not leave without my numbers. Did they always ask the cabin crew to move that one passenger from zone b to zone c? I have no idea. From my point of view my neck was clear of the noose because I had a good load sheet and the numbers I gave them were on the cockpit voice recorder. I'm sure some captains probably asked the cc to move that person, some probably did not. That was up to them.


So.....what we have here in the original post is a situation where numbers needed to be corrected to get an in trim aircraft on paper for the files and obviously a captain who wanted the change to actually be made, that's his perogative. What we also have is a person who claims to be a pilot and yet when told he needs to move for w&b purposes gets all uppity about it. Maybe he made it known that he was a pilot and the CC thought he would be the most co-operative person to move because of that. Maybe he was actually deadheading free of charge, if that was the case I'd throw him off if I was the captain.

Anyway I could go on about other systems but I think that's enough to answer the questions.

Oh and as to whether the aircraft would fly ok without the adjustment, I know of an airline that was fined big time when it had a B737 takeoff with a load sheet that was so wrong the take off center of gravity was not only outside the envelope it was outside the margins of the graph and almost off the page!!!! The agent doing the load sheet had reversed many of the numbers when extracting them from the books.
I ran the numbers for that flight myself and was amazed that the aircraft completed the flight without crashing, but it did.

So there you have it.
Hope that helps.

[john_tullamarine]

I would have to fix it by adjusting the passenger zone numbers

The Excel system you cite appears to be dreadfully cumbersome. One wonders why the operators didn't choose to have the flightcrew just run up a loadsheet on the flightdeck .. ?

as to whether the aircraft would fly ok without the adjustment

As in so many things .. it depends.

In essence, the aircraft, as certificated, is reasonably easy and nice to fly.

If the CG is permitted to move aft, especially, things can get out of hand.

At the aft limit, the aircraft will be compliant with the Design Standards.

As the CG moves outside the aft limit, the static stability reduces. What the pilot finds is that the aircraft (in pitch) becomes progressively twitchier with lesser stick loads causing greater responses to the pitching flight path .. ie the aircraft gets more difficult to fly accurately and the pilot has to spend more of his/her cognitive capability keeping an eye on what's going on. Indeed, the risk of pitching structural overload increases rapidly.

As the CG moves further aft, we move from a condition of static stability to one of static instability. In this situation, the aircraft should be flyable but the workload is extremely high and the pilot techniques required are quite different to those used normally. In general, the typical pilot without flight test knowledge and experience will fail in the task and the aircraft will be lost.

As the CG moves yet further aft, the aircraft moves into a CG situation where it becomes dynamically unstable and beyond the capability of a human pilot .. loss is inevitable.

[hb78]

As a CSM I am not trained in weight and balance, and have only a very minor knowledge of it I leave that job to the professionals. I do however have a healthy respect for the flight crew and Captain, knowing that they are trained in this area and have an overall responsibility for the aircraft and its occupants.

I have been asked to move pax once boarded for a number of reasons. The majority of the time it has come directly from the Captain in relation to weight and balance issues (which they have not stated every nuance of). I have then requested the passenger to move and passed on the direct reason to the passenger and apologise for the inconvenience. Most are satisfied with this response.

Other reasons I have asked passengers to move are incorrect seating allocation (incorrect class) or to seat a family or friends together when not allocated together. I have never asked a guest to move to ease the cleaning of the aircraft (nor heard of this) and I find it hard to believe anybody would.

In regard to frog marching a passenger off the aircraft, if they disobey a simple request to move seats due to an operational issue during boarding before the doors are even closed, how are they going to respond to another more urgent request with a few scotches under their belt and no one to call for help besides my small team! You need to appreciate that we are locked in a metal tube with 200+ people with only a few cabin crew to manage and ensure that all safety and security is complied with. If I fear for my own (or crew) safety or that of the aircraft is compromised that person would be taken of the aircraft, but this is a generally extreme response only.

The original post seems to say the CC asked the OP to move in quite a random fashion and when the OP said no, they simply moved on thinking nothing more of it. I do find this hard to believe, as they say there is always three sides to a story, yours, mine and the truth!! I think some (not all!) Flight crew believe all we do is serve drinks and food, then sit down the back and have a gossip. This is like some CC (again not all!) who believe all flight crew do is sit up the front with their newspapers and press a few buttons. This is not an accurate representation of either job and it becomes dangerous when either group starts assuming because they have a little knowledge of either role that they know better and can question simple instructions. What if I as a CSM simply diregarded the Captains instructions to move someone because "what could one person moving make a difference? Hmmmm, I won't bother". Chaos would ensue. What instructions do I then follow and which ones do I not.......

At the end of the day I don't think we will ever know what happened on pd2's flight, as even he stated it was his perception, but I would stress that if CC ask you to move there is a good reason and if you are not happy with the reason provided, ask to speak with the CSM for clarification (which I would be happy to provide). Failing that, by all means make a complaint directly to the airline, if there is a reason other than operational requirements then the airline should know. But to be on the safe side, move........There maybe something that you, as not part of the crew, are not aware....... I am not trained in weight and balance, I simply enforce the directions given to me by those trained in this area and enabled by the airline to delegate these directions to me.

And let's not forget that whenever you buy a seat on an aircraft, one of the conditions is that you will follow all directions of crew, there is no disclaimer that states "but only if you agree with it or don't find it silly!"

[ozangel]

I find this whole debate extraordinary!


A 'passenger' was asked to change seats - for safety reasons.

The cabin attendant surely didn't ask this of them to be difficult.

Anyone who's done the job knows that there's little time to action such necessary aspects of the role - and most do it in a respectable yet firm manner.

The only 'downside' to this whole story is that the passenger was not offloaded (given the refusal) - lest he/she delay 100+ other passengers of an on time departure.

The passenger has no right to question the authority of the captain - and is greatly mistaken should he/she feel entitled to an explanation from the aircraft commander. The cabin attendant was no doubt acting upon his order - or policy that dictated that only appropriate persons be seated in such rows.

In every other aspect, flying aboard a sophisticated airliner may have become akin to travelling on a bus - but in no way does that give passengers the right (whether they realise it or not) to question the intent of those employed to keep the airliner safe. How much a passenger has paid has absolutely no influence on the crew's obligation to carry out their duty safely.

Unless you are rostered by the airline to operate the flight upon which you travel, you have absolutely no right to question the actions of the crew - whether you are a commercial pilot or not! Show some respect!

Before anyone argues with my sentiment - ask yourself - would your airline back you up if someone was hurt/killed because you put customer service ahead of safety?

[Piltdown Man]

I can see where pd2 is coming from. I used to fly various Fokker (F27/50/100) aircraft that would depart with the just the headcount being correct, unless we were very light when we were told something like "nobody aft of row n". Then one day, we introduced loading zones and the numbers in each zone had to agree with the loadsheet. Some people (Flight deck as well as CC) felt they were unable to depart if there was any disagreement between the loadsheet and the numbers of passengers in each zone. Obviously that cannot be correct and I know for sure that many people were unnecessarily moved to make the loading comply with the paperwork. Unfortunately, these people were probably incorrectly told that they had to move for safety reasons. Personally, I performed a trim change calculation to stop passengers being moved without good reason. But, and here's the but - if I determined that a change needed to be mode, it would be done. And the people I would move would be those in the middle and aft. I'll not disturb the premium fare passengers at the front unless I really have to. But if anybody said to me (or my crew) that they were not moving, that would be the last conversation before they left the aircraft. And one or two did.

Would it make a difference if you flew a 40 ton aircraft with one passenger's worth of trim error? Probably not but. But I'm not a test a pilot and have no idea how much margin I have outside the loading envelope, both for takeoff and in flight. The reason I've asked for change is because the CofG is outside the boundary I've been given.

But may I suggest that we may about to have a new reason to move passengers - for fuel efficiency. An aft CofG can save an appreciable amount of fuel and my company are moving towards more fuel efficient loading. The request to move will remain and we'll expect it to be complied with. Only the reason will be different.

PM

[Checkboard]

Appendix 1 to EU-OPS 1.1005
Initial safety training

...The subjects that must be covered as a minimum by a course of initial safety training referred to in OPS 1.1005 are:

(e) Passenger handling:

4. the importance of correct seat allocation with reference to aeroplane mass and balance. Particular emphasis shall also be given on the seating of disabled passengers, and the necessity of seating able-bodied passengers adjacent to unsupervised exits;

Hmm so it seems the Cabin Crew Member was doing their job, according to the applicable law ...

EU-OPS 1.090
Authority of the commander

An operator shall take all reasonable measures to ensure that all persons carried in the aeroplane obey all lawful commands given by the commander for the purpose of securing the safety of the aeroplane and of persons or property carried therein.

EU-OPS 1.085
Crew responsibilities

The commander shall:

3. have authority to give all commands he/she deems necessary for the purpose of securing the safety of the aeroplane and of persons or property carried therein;

4. have authority to disembark any person, or any part of the cargo, which, in his/her opinion, may represent a potential hazard to the safety of the aeroplane or its occupants;

So, a person who has proven that they are unwilling to obey the safety commands of the cabin crew has also proven they are a risk for further flight during any problems that may be encountered down route. Lucky you weren't on my flight then ....

[trex450]

pd2,
unfortunately it doesn't matter where people come on the foodchain or how professional people are (just because they are trained to be professional does not mean that there are not the odd few who don't act accordingly 100% of the time) there will always be some who like to throw their weight around because they think they can. Sounds like you got one there!

I had a similar case years ago when travelling with my year old child. The flight was delayed such that it was departing in the middle of the night, child had not slept yet so was grumpy but once on was happy so long as he was stood on my knees looking about. He was far from happy and vocal about it when sat on my lap with the seatbelt on. It goes without saying that all the other delayed, tired, grumpy pax were finding this an irritation as well. I had a stupid, impractical steward who tried to tell me to strap him in (in accordance with the signs) despite me repeatedly telling him that the engines had not even started and that for the benefit of everyone else concerned that he would stay standing. The steward was sat two rows away so it was easy to communicate with him. I did point out to him (very arrogant and uncoporative as it is to question what a member of the crew is telling you I know) that for the benefit of everyone within about 20 rows I would ensure that my child would be safely secured well before take off.

[Seldomfitforpurpose]

trex,

Folk like you have no real capacity to think through all of the "what if's" and the implications for the well being of others around you. The safety rules are written for very good reasons and as such folk who think they know best and simply flout those rules have no place on modern aircraft and should be denied flight at all times.

In your scenario imagine if the aircraft is cleared for push back, the tug driver has a bit of a "heavy right foot", the aircraft lurches rearwards and you lose your grip on young grumpy who clatters to the floor.

If he's injured then young grumpy now needs off loading with all the inevitable delays thet entails and in the "where theres blame theres a claim" world with live in the airline finds it has another lawsuit from a Clampet Family member who thought he knows best.

If the CC tells you to do something there is always a very good reason for it and as such it is a passengers duty to comply.

[trex450]

Seldom,
I forgot to mention then that I have more than a few thousand hours command time, almost a thousand hours as passenger, the aircraft did not require pushback, I was very familiar with the airfield in question, was not challenged by any other crew members and finally I guess am aware of the "crew seats for take off" pa call. In addition to that a year old child using the child seat on a parents lap is at much higher risk of injury than in any other position.
lol

[Avitor]

Only 50 passengers on a Monarch flight, we were requested to sit in the first 15 rows for take off, afterwards we could move, we were told, if we felt like it.

100% compliance. <and why not?>