Pipistrel Virus 912, Flight And Maintenance Manual

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Sample c.g. calculation
Guidelines
Gtotal is the total mass of empty aircraft. All calculations can be performed with aircraft empty
weight and empty weight centre of gravity (c.g.), as the pilots sits directly below the centre of gravity
and do not cause the c.g. to be shifted. The amount of fuel quantity also has no impact on the c.g..
WARNING!
Both pilots’ weight and weight of fuel do not influence c.g. or their influence is
insignificant. However, baggage can influence the c.g. severely and may cause the aircraft to
become uncontrollable!
Basic CG formulas and calculation
The below instructions are valid for Virus Tail Wheel and Nose Wheel editions. Read thoroughly. Note
also that the basic c.g. at 287 mm will be used purely as an example.
First, weigh the aircraft according to the procedure described in this chapter and write down values
of G1 (sum of scale readings at main wheels) and G2 (scale reading at tail/front wheel). Then calcu-
late the position of c.g. in milimeters (mm) from the datum (wing’s leading edge at wing root).
For Tail wheel edition of Virus use the following formula:
where:
G2tail
is the scale reading at the tail wheel,
Gtotal is the sum of G1 and G2tail (G1+G2tail), a.k.a. aircraft empty weight
a is the distance from main wheel axis to wing’s leading edge,
b
is the distance between main and tail wheel axis.
For Nose wheel edition of Virus use the following formula:
where:
G2back is the sum of scale readings at both main (back) wheels,
Gtotal
is the sum of G1 and G2back (G1+G2back), a.k.a. aircraft empty weight
a is the distance from nose wheel axis to wing’s leading edge,
b is the distance from main wheel axis to wing’s leading edge,
c = (a+b)
is the sum of both distances above.
Second, determine the c.g. position in percentage (%) of Mean Aerodynamic Chord (MAC) with fol-
lowing the formula:
where:
CGmm is the position of CG in milimeters (mm),
R
is the difference between wing’s leading edge and MAC’s leading edge (29 mm),
MAC is the Mean Aerodynamic Chord (908 mm).
CG
G b
G
a G
mm
G
mm mm
mm
tail
total
tail
total
=
·
+ =
·
+ =
2 2 4300
110 287
CG
G c
G
a G
mm
G
mm mm
mm
back
total
back
total
=
·
- =
·
- =
1 1 1525
1020 287
Weight and balance
CG
CG R
MAC
mm mm
mm
MAC
mm
%
. %
=
-
· =
-
· =
100 287
29
908
100 28 4