MD-80 loadsheet - Adjusted Weight Loading System.

[Dadanawa]

Does anyone out there have a sample MD-82 loadsheet ? I'm designing a combination load and trim sheet and would like to look at what is out there.

I have a sample from Transmeridian. They use the Adjusted Weight method along with tables for each combination of pax, fuel, cargo. I plan on designing a computerized version that plots the ZFW,TOW, and LDW within the envelope using a y-axis of weight in lbs and an x-axis of index units, and including % MAC lines.

While at it does anyone know the formula to calculate the Adjusted Weight using % MAC. Confirm the basic weight is rounded up to the nearest 100, and the % MAC is added to this figure.

e.g.

Basic weight: 82251, % MAC: 34.9
Basic weight rounded up: 82300
Adjusted weight = 82300 + 34.9
= 82334.9
The last two digits represent the % MAC = 4.9.

Does this sound right ?

Thanks

[john_tullamarine]

Methinks you are embarked on a course of disaster at the moment ...

Does anyone out there have a sample MD-82 loadsheet ?

Be VERY careful pinching other loading systems or trying to use them for design work if you don't have a really detailed knowledge and understanding of how loading systems are designed and what limitations are inherent in the various methodologies. Each is tailored to a specific Type, model, and configuration and, indeed, one can generate 10 quite different trim sheets (or other loading systems) for the same aircraft .. all looking quite different and using quite different numbers .. but all giving accurate and acceptable results.

.. do please be wary of traps for young players unless you know what you are about with design of trimsheets.

I have a sample from Transmeridian.

Consider posting an image and we have something concrete for discussion.

They use the Adjusted Weight method

what, pray tell, is that ?

along with tables for each combination of pax, fuel, cargo.

one would ask why ? For this class of aircraft a conventional trimsheet wins out over load tables every time.

I plan on designing a computerized version that plots the ZFW,TOW, and LDW within the envelope using a y-axis of weight in lbs and an x-axis of index units, and including % MAC lines.

ie a computerised version of a trimsheet. Generally a waste of time as the graphical bits are not necessary with the computer's number crunching power. Be very wary when drawing pictures that you understand which lines are straight and which lines are curves.

While at it does anyone know the formula to calculate the Adjusted Weight using % MAC.

Again, tell us what Adjusted Weight might be and we might have some chance of leading you along the road

Adjusted weight = 82300 + 34.9 = 82334.9

First, why would one round up the BW in such a fashion ? Second, this non-equation constitutes adding apples and oranges to end up with garbage. First requirement for any equation is that the units make sense. This purports to add weight and a non-dimensional number to get something undefinable.

Does this sound right ?

Afraid not ...

[Dadanawa]

Hello John,

Thanks for responding. I figured only you would understand what I was talking about.

Adjusted Weight calculations are used mostly in America in designing loadsheets with tables.

Adjusted Wt. using index formula:

Rounded Wt. + [Actual Wt. x (B.A.-Datum)]/(Moment Constant)
+ Datum Constant.

What results is a combination figure of mathematical weight and mathematical moment. Pretty neat. eg for an Adj Wt figure of 82334.9 The 4.9 at the end would represent the trim units in % MAC (in this case).

Anyway,what I'm working on is the simpler AHM 560 type loadmessage with a trimsheet graph included (see personal messages). This is straightforward. All information derived from the TCDS, weight and balance manual, weighing report, LOPAs, etc. There are no curved portions of the envelope since all the variations are straight-line. Curtailments are built in as necessary. There are plots for TOW/MAC, ZFW/MAC, LDW/MAC.

Contrary to what you may think, I'm not exactly a beginner when it comes to loadsheets. I've studied them for years.

Glad to hear your thoughts.

E.

[john_tullamarine]

Rounded Wt. + [Actual Wt. x (B.A.-Datum)]/(Moment Constant) + Datum Constant.

.. if this is one side of an equation, the units are inconsistent - something's wrong.

There are no curved portions of the envelope since all the variations are straight-line.

The only WT/IU envelopes with straight lines are the simplest seen with very small aircraft. Otherwise, generally, all have curved portions. Then again, you may be using tabular data to input only the final WT/CG in which case the envelope will present as straight lines for most aircraft

Need to see what you are playing with to offer further comment.

[Dadanawa]

Hello John,

Would it be possible to get an e-mail contact where I can send you the PDF file ?

Ev.

[john_tullamarine]

[email protected] is a useful spot for email attachments.

[Dadanawa]

I've sent you the excel file as a pdf.

Thanks.

E.

[john_tullamarine]

Thanks for the loadsheet - appears to be fairly typical of that genre. Suggest you post it as a graphic for discussion.

Where does the "adjusted weight" comes into play ?

[Dadanawa]

Hello John,

I don't know how to post a PDF file as a graphic. Can you assist ? Will it have to be in JPEG format ?

Thanks.

Ev

[Dadanawa]

Adjusted weight or the mathematical combination of weight and moment into one figure is used with a different type of loadsheet system.

Each item of pax, cargo, or fuel has its weight adjusted by a formula that gives a new number. The sum of the APS adjusted weight, pax, cargo, and fuel(adjusted weights) gives a takeoff adjusted weight whose last three digits represent balance units (usually %MAC units).

I have the formula for adjusted weight using index units but the one %MAC, I can't get to grips with.

Ev.

[john_tullamarine]

Posting graphics to PPRuNe (http://www.pprune.org/spectators-balcony-spotters-corner/203481-image-posting-pprune-guide.html) guidance.

I have the formula for adjusted weight using index units but the one %MAC, I can't get to grips with.

I think that we need you to type out your formulae so that we can offer comment - all sounds a bit strange to me - I'm sure we can sort it out once we can see the details

[Dadanawa]

Here is the excel loadsheet for the MD-82. I will post the formulas for adjusted weight.
http://farm6.static.flickr.com/5003/5260100541_555a91f8a1_z.jpg

[Dadanawa]

http://farm6.static.flickr.com/5210/5260800150_b8e72f1416_z.jpg

[john_tullamarine]

Ah .. progress.

The index equation (#3) makes it clear what is going on as it concatenates the weight with the standard IU calculation.

In a conventional manual tabulation style of calculation one would total weight and IU values taken from tabulated data sheets. The resulting totals would then be plotted on an envelope to test for correct loading.

What the adjusted weight technique does is concatenate the two columns by rounding off the weight entries to make room for the IU values. Innovative but, in my view, not a great deal of value in the field ?

My concerns are -

(a) the technique introduces an increased level of error via round off considerations for both weights and IU.

(b) the technique is so un-intuitive and not amenable to commonsense (sanity) checks by the person running the sums that I would expect an increased level of arithmetic errors and, in all likelihood, some occasional significant error events.

(c) design considerations would need to be constraining to avoid ill-conditioned results and a nonsensical IU total.

(d) error considerations dictate that it not be used for small aircraft

(e) doing the same calculation set via a load and trimsheet for a larger aircraft would provide both better accuracy and quicker results. Indeed, using a load sheet tabulation for weights and a prayer wheel trimsheet for the IU calculations would win hands down every time for speed and accuracy over the adjusted weight technique.

It needs to be kept in mind that a well designed trimsheet is as accurate as a longhand calculation to all practical intents and purposes .. assuming a modest endeavour to execute the working with a little care.

That is to say, the adjusted weight technique is workable ... but why would anyone want to use it ? I just don't see any rational advantage to be gained.

However, I stand by for those who have used such systems routinely to offer contrary comment .. it may well be that my concerns are unduly conservative due to unfamiliarity with using the technique in the field.

I will have to play with #1 and #2 to see what is going on there as the relationships don't offer any immediate understanding.

Perhaps you might define what is meant by

(a) reference weight

(b) BA/trim unit

(c) datum trim unit

(d) BA/%MAC

(e) datum%MAC

as none readily fits with an attempt to start with #3 and derive the other relationships.

[Dadanawa]

John,

My sentiments exactly. However thats what they want.

Anyway, let me try and decipher some of your queries.

Formulas for the MD-80 series:

Index = ((Wt*(Arm-922)/1000)) + 5000. 922 is the Datum.This formula is not for individual items. For individual items remove the 5000.

% MAC = ((Arm-885.547)/158.512)*100. LEMAC = 885.547, MAC = 158.512

Forget the Stab Trim Equation for the moment please. Regarding the % MAC Equation:

Reference Weight: I have no idea what that is.

Balance Arm / %MAC: Each 1 % MAC change corresponds to a certain amount of inches of arm movement, in this case 1.6 inches.

Datum %MAC: This the Datum in inches converted to %MAC. In this case 23%.

Boeing guys help us out here please.

I think this information is available with access to My Boeing Fleet.

Ev.

[john_tullamarine]

That's cleared up several points.

Boeing guys help us out here please

Are you seriously suggesting that Boeing developed this method of doing things worse than the conventional way ?

[Dadanawa]

Here is the original problem:

For the fuel weights below, how did they arrive with the adjusted weight units shown?

Fuel Weight-lbs. Arm-in. Adjusted Weight Units.

10000 937.1 10001.4
15000 944.8 15002.7
20000 946.5 20003.7

The bold figures are the balance units (%MAC) concatenated with the weight.

Any ideas?

[scotiat]

Guys,

I have followed your discussions with interest and I would say that in my experience I would not recommend the use of adjusted weight index system over other methods (tabular or dropline) as I personally feel that any benifits are out weighed by the negatives.

The essence of the Adjusted Weight Index Loading System (AWIS) is that balance units (expressed to one decimal place), are added to each element of weight on the Load Manifest, to give adjusted weights.

When these adjusted weights are summated, they provide both an aircraft weight, indicated by the digits to the left of the decimal point, and the Centre of Gravity (C.G.) value, indicated by the right hand digits.

Balance Units are increments of moment about a reference datum, and at take-off they correspond closely to Mean Aerodynamic Chord (M.A.C.).

The datum must be selected and is normally a typical take-off weight with a lever arm located at the aircraft Centre of Gravity datum.

An example Datum for a B767-200 would be :-

320000.0 lb. 24.0 % M.A.C.

Balance units will correspond exactly to % M.A.C. at the above datum weight.

HOWEVER, At other take-off weights the degree of accuracy decreases the further away the actual take-off weight is from the datum take-off weight.

[FONT=LotusLineDraw][FONT=Arial][COLOR=#000000]If you need any further assistance with this or other W&B problems, please feel free to contact me by PM.

[Dadanawa]

Thanks,

You have shone a light in a dark corner. I did not realize that the reference weight was an average takeoff weight.

Makes a lot more sense now. I can see the errors with a large variation from the average.

I will send you the PDF of the other version of the loadsheet. The nor I'd rather use.

Ev.

[john_tullamarine]

This thread is starting to confuse me mightily. It may be that folk are being a little lax in the use of terminology .. and, I note, I am regularly guilty of the same .. However, the subject material is pretty important to flight safety so it is worth gnawing at the bone until we get it sorted out ..

The bold figures are the balance units (%MAC) concatenated with the weight

I suggest not.

%MAC is just another way of writing CG.

One cannot add CGs of loads to end up with a final figure with any sense. The addition has to be one of either moment or IU.

The bold figures, presuming they are IU, can be derived easily if one has, as the IU equation, a trim datum of 905 and a IU constant of 225000. This equation may not be precise as we only have three examples to play with, With a few more example combinations. it could be refined quite easily.

When these adjusted weights are summated, they provide both an aircraft weight, indicated by the digits to the left of the decimal point, and the Centre of Gravity (C.G.) value, indicated by the right hand digits

So far, searches of the net and this thread have given nothing concrete as to the derivation of the method (other than for the index equation which is quite conventional). Probably, I am going to have spend some time trying to make sense of the two other "equations" cited in the earlier post ...

Unless someone can present a rational derivation, it is my present contention that you cannot add CG values to get any sensible result ....


The essence of the Adjusted Weight Index Loading System (AWIS) is that balance units (expressed to one decimal place), are added to each element of weight on the Load Manifest, to give adjusted weights.

When these adjusted weights are summated, they provide both an aircraft weight, indicated by the digits to the left of the decimal point, and the Centre of Gravity (C.G.) value, indicated by the right hand digits.

Balance Units are increments of moment about a reference datum

(My bolding)

You can't have it both ways .. what are balance units ? CG or moment values ?


Balance Units are increments of moment about a reference datum, and at take-off they correspond closely to Mean Aerodynamic Chord (M.A.C.).

At the risk of offending, I suggest that the second part of your statement is nonsensical. The MAC is a fixed length so, if your statement were to be corrent, balance units would be invariant and pretty meaningless ? If you mean %MAC, then how does one relate a moment to a CG .. other than to the extent that, as the moment increases in number line magnitude (ie to the right), the CG moves aft ?

The datum must be selected and is normally a typical take-off weight with a lever arm located at the aircraft Centre of Gravity datum

Again, this appears to be nonsense. Datum is a position on the fuse station line .. ie a distance from somewhere else but, now, you are suggesting it is a weight ?


An example Datum for a B767-200 would be :-
320000.0 lb. 24.0 % M.A.C.
Balance units will correspond exactly to % M.A.C. at the above datum weight

The datum might well be 24%MAC but has naught to do with 320000lb. Can you provide the balance units value for your example and that might lift the veil of confusion somewhat ?

yours in confusion .... JT

[john_tullamarine]

I've had a play with the relationships cited in post #13 trying to end up with the two earlier relationships from first principles and starting with the presumed guidance of #3 .. with little success. Possibly my lack of imaginative manipulation so I need a little guidance regarding the goalposts, I guess.

I am presuming that each intends to achieve the same result, viz., a concatenation of a weight and an index .. in each case with the arm information represented as %MAC and stab trim setting units, respectively.

Now I see that scotiat claims some considerable competence in the subject in his cited website so, perhaps, I can ask him to give the horse a touch of the spur by setting out a simple example calculation for, say, a postulated light aircraft. That should sort out the confusion with terms and definitions very promptly.

As I suggested earlier, this is an important topic from a safety viewpoint and it is worth working through the detail for the benefit of

(a) me .. as we don't appear to use the technique in Australia and, at this point, I am a tad confused in that I appear to be unable to derive what ought to be a comparatively trivial engineering calculation

(b) the new chums .. as they possibly know less than I do about the weight control subject.

[Dadanawa]

Hello John,

I'm going to send you the entire chapter from which I posted the image on post #13. It may be of some help. As you rightly said earlier, there is little or no information on this method calculation, and maybe for a good reason. Modern systems certainly don't use it that often.
The Index equation for adjusted weight makes sense. But the %MAC one needs clarification.
Maybe somebody out there would have a weight and balance manual from a time when this was popular that would explain further. I have a USAir BAe-146 Pilot's handbook that uses this method but no explanation, only a sample. Also I flew a YS-11A from Mid-Pac airlines that used the same. Seemed to be popular in the US circa the 80's and early 90's.

We will crack it I'm sure.

[Herson]

Hi! Can you send me the Excel File of the Loadsheet that you designed for the MD-80? I just want to have a good reference because im also designing a loadsheet of both dornier & boeing aircrafts. by the way this is my email. [email protected].

[scotiat]

John,

I have specialised in aircraft weight and balance for over 18 years.

I fully understand the differences between dropline, tabular and AWIS systems.

I apologies if I have added to any confusion, but I will happily send sample loading systems and substantiation reports for AWIS systems if you provide a contact email address.

I cannot post this on the web as it is company IP.

I fully appreciate that w&b is a very safety critical issue and I have also seen many examples of how trimsheets can be produced with serious errors when the author has little knowledge or experience. Thus why I am willing to assist.

[djallamitou]

Hi john

I really enjoyed reading all the previous comments that s helped me to understand a lot of things.

I am a flight dispatcher in a handling comapany so i work with many airlines and i have to do many manual load sheets so i got the idea to do an excel load sheet wich i found realesed already here on this formum :ok:
finally i realesed my own excel load sheet of the vueling airline a fleet of 41 aircratf A320/214.
I want to share it with you, i compare it many times with the automatized load sheet and the result were 95% the same.
here you will find a jpeg copy maybe you help me for any detaills

[john_tullamarine]

Discrepancy ought to be rather less than that.

Generally, the main bits which give problems are associated with

(a) centroid approximation for a loading area

(b) figuring variable things such as occupant movement in flight

(c) linearising fuel arms

and then the error analysis (which ought to be, but is not always, done) which may fudge the sheet CG limits to make the completion conservative.

For spreadsheets, if they are to be used by others, the main concern is protecting against third party errors in use compromising the calculated results.

By all means send me a copy and I'll have a looksee.

[djallamitou]

hello john

I do i understand all those problems in the CG, moment and fuel effect wich are very difficults to calculate and generate a perfect load sheet.
But we have the right to try and learn from our mistakes.
Anyway i will send you the excel load sheet wich i realsed with a pdf file explaining how to use it, I will send it to this email [email protected]

I will await your reply.

[djallamitou]

hi john

I sent you the excel loadsheet but i didn't get your reply so i want to make sure you've recieved my email. pls answare.

[john_tullamarine]

Received OK, thanks. Will review it in the new few days and get back to you. Regards

[nobbyknownowt]

Hello all

I'm just wondering if you ever got anywhere with this as its highly topical for me just now?... We are putting some aircraft into someone elses fleet and I am tasked with creating a loadsheet similar to their own in order to reduce differences between types, a trawl of the web returned this discussion.
Unfortunately the people that are now responsible for their weight and balance don't seem to even understand that their loadsheet is an adjusted weight/stab loadsheet so when I ask for their loadsheet formula data they just provide the standard data from the WBM which I already have.
All I get from them is moving "x" passengers moves the trim by "x" units and can we do the same!
I am guessing they got the loadsheet from Mr.Boeing as a package and they are keeping their secrets close to their chests.
So I am left with the task of trying to deconstruct what they currently use in order to understand it and adapt it for a new type. Undoubtedly the variables can be cracked in time but the deadline is approaching and without the loadsheet type I cannot even start on operational margin calculations (the inaccuracies of this system will affect the envelope).
The last time I worked with adjusted weight loadsheets was in the 80s and to be honest thought them to be extinct.
If you got anywhere with understanding the logic I would be grateful to hear anything before I make a decision on if I can offer this type of sheet or not.

thanks
Nobby

[john_tullamarine]

I have to apologise as I put the thread to one side and promptly forgot all about it. Bit busy for the next week or two but will endeavour to have a further play with it then.

Operators wanting to keep the same style of sheet can be a tad tedious but that's the way things go ....

[roulishollandais]

Dear John,
Your patient answers were perfect and enough.I do i understand all those problems in the CG, moment and fuel effect wich are very difficults to calculate and generate a perfect load sheet. But we have the right to try and learn from our mistakes. It is not difficult, and you are not allowed to do mistakes in loadsheets! Nor to learn from mistakes on loadsheets! :ugh: I hope the Captains will refuse to sign such papers.

[john_tullamarine]

The adjusted weight thing now makes a little more sense.

Recently, I came across an old (dating almost back to Pontius's days ..) tech paper presented by (I presume) the Boeing engineer who developed the system.

Apparently in the early second generation jet days, pre-electronic computer .. ie early 60s, some Boeing customer airlines were a bit anti-trim sheet style load systems and, while accepting that computers would do the day to day work in a few years to come, wanted a simple addition only style system in the meantime which combined all the bits (weight, CG, and stab trim calcs) in the one all singing all dancing technique. This then would allow them to do the load work on the turn around using traditional pencil and paper assisted by the old mechanical adding machine .. now, I remember those ... how many others here do ?

A chap named Saunders (the above engineer) came up with a concatenated system which, for the sake of some minor rubbery weight approximations, facilitated the requirement.

When I finish working through the technique (ie when I figure out just how it all works) and can relate it satisfactorily to the Boeing PPT link shown earlier, I'll come back with some explanation.


As nobbyknownowt suggested, the technique appears to have been intended as a (pre-computer) stopgap and probably has little relevance today other than as a curiosity .. albeit that some operators still hold to it as a procedural technique.

[horaciogdeidda]

Estimados:

Buenas noches, mi nombre es Horacio, soy estudiante de Despachante de aeornaves, estoy realizando las practicas y me gustaría saber si a través de este foro, podría conseguir las planillas de carga del MD80, A320 A380, B747-800, ART72, CASA C-295, CD-10, CD9, E190, C-130, y sus respectivas tablas de index,

Disculpen se que es mucho pedir, pero me gustaría tener una ampliar variedad para la práctica, gracias y disculpen las molestias.

Este es mi correo [email protected] celular 541164878010.