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Weight and Balance
The correct weight and balance of an aircraft is critical for
its safe operation.
Any changes that may adversly affect this safe operation ie
the addition of a larger battery must be approved by a GFA
qualified person.
The following program written in Microsoft Excel 2003 will
allow the calculation of weight and balance requirements in
accordance with the,[download] BASIC SAILPLANE ENGINEERING
manual.
The program which has evolved over the past 7 years follows as
closely as possible the GFA weight and balance forms,
[download ] W1 and W2.
No fancy computer skills are required other than the ability
to use the keyboard and mouse.
If you are using Excel 2007 only use the compatibility mode as
the huge increase in the available number of cells can cause
problems.
The program consists of several parts which we will explain as
we go.
The first is the W1 sheet, the areas in BLUE are for user
povided information and as can be seen looks very much like
the standard GFA W1 form.
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After the aircraft is weighed in accordance with the manual
the various measurements are keyed into their respective areas
(BLUE).
As soon as all the information is keyed in the results of
these measurements will be shown in ORANGE areas.
It should be noted the program will only allow information to
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be entered in the BLUE areas.
The program has a data base which contains information on a
number of aircraft from their Type Data Sheets, this data base
can be user updated when required.
One feature that this data base has allowed is a drop down
menu in the location where you would normally insert the type
of aircraft.
A click of the mouse in area as shown above will will bring up
a list of aircraft in the data base; select the aircraft type
you want, an ASK21 Mi in this case as an example.
Selecting the aircraft that you require has two functions
first it leaves the name in the box, second is that all the
information in the data base for the selected aircraft is
transferred to the calculation sheet.
An explanation for the quick calulator seen to the right of
the main W1 sheet after it has been downloaded.
If the scales used to weigh the aircraft do not have the
required accuracy (100grams)to weigh the tailwheel, a separate
set of scales must be used. This calculator allows to input
the total weight (G) of the aircraft and when the tail wheel
weight is entered int the W1 sheet the calculation of the main
wheel weight (G1)is done automatically and transferred into
the W1 sheet.
The CALCULATION sheet takes this information as well as the
results from the W1 sheet to perform most of the calculations
for the weight and balance of the aircraft.
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This sheet has no user inputs all the information is gathered
from the W1 sheet and the data base. It shows a number of
basic calculations such as the minimum pilot weight,the empty
c/g, the safe c/g plus some information if it is a two
seat aircraft. It also shows what equations where used top get
these results,see manual.
This information is the automatically transferred to the
PLACARD sheet.
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This sheet then shows such information as minimum and maximum
pilot weights,maximum fuselage load, if applicable the effect
of carrying water as well as fixed items as required by the
manufacturer.
From this sheet the information can be transferred to suitable
material for the placards.
W2 sheet
This sheet allows number of user entry's which can be used to
verify that a modification to the aircraft ie that extra
battery does not cause the aircraft to move outside the
allowable limits for both c/g position or weight limits
All the calculations are done automatically and will be
displayed Red if they are outside the limits or Green if all
is ok.
To save all the information click of File, Save As and change
the name of the file,it can be your choice but is best if you
use the aircraft registration letters.
The program does not cover all possibilities and attention
should be paid to the manufacturer's requirements. Some
aircraft like the DG 1000 which can have up to 12Kg of
removable ballast in the tailfin require special attention, in
some powered sailplanes the location of the fuel tank can have
a great effect on the c/g as well as the all up weight.
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This program makes doing the calculations very easy but it
does not take away the duty of care of the user to ensure that
all the information is correct.
There are a couple of other features to the program which may
be of interest and of some use, if you are interested I can
give you the details.
The program is presented as is and is totally for you to use
as you wish, I make no promise that it is 100% accurate that
is where your duty of care comes in, I only ask that if you do
make any modifications that you think are worthwile that you
let me know.
As noted earlier program was written useing Microsoft Excel
2003, I have used Excel 2007 without any problems just use the
save as 97-2003 option and click "continue" when it comes up
with the compatability screen.
Cliff Wylie, lwyl5744@internode.on.net, I will answer all
mails.
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