STEMME S12, Maintenance Manual

Page: 146 / 290

DOCUMENT NUMBER:
L500-912.820 ISSUE JUL 20, 2016
AMENDMENT: 00
DATE: --
CHAPTER- PAGE 6-4
MAINTENANCE MANUAL STEMME S12
Following an aircraft repair, painting or modification of equipment it always must be verified
that component weights, empty weight and CG at empty weight are still within certified limits.
If weight and arm of removed or installed equipment is known exactly, change of empty weight
and CG can be calculated. For calculation of empty weight CG, the arm of removed or installed
equipment or components is to be entered into the »Weight and Balance Report« (see Annex D).
FORMULA
x
neu
= m
alt
· x
alt
+ m
zus1
· x
zus1
+ m
zus2
· x
zus2
+ ....
m
neu
ABBREVIATIONS MEAN
- m
alt
: Empty weight according to last weighing report
- x
alt
: CG at empty weight according to last weighing report
- m
zus
: Weight of added component
- x
zus
: Arms of added components with reference plane (RP)
- m
neu
: Resulting new total empty weight
- x
neu
: Resulting new total empty CG
Minimum load due to the modification can be taken from figure 6.3.b. and 6.3.c for two differ-
ent loading conditions.
CAUTION
Basically the arms of weights in front of the reference plane (RP)must be counted negative, those
aft of the RP positive for any calculations.
If the effect of a modification or repair cannot be calculated (e. g. when having painted or fol-
lowing a repair of the composite structure) the aircraft must be weighed again.
To keep empty weight CG for unchanged minimum load within certified limits, it may be necessary
to install ballast at the front gear frame or at the aft part of the tail wheel bay (rear web of fin).
The required weight of the ballast can be calculated:
m
Ballast
= m
alt
x
neu
- x
alt
x
Ballast
- x
neu
Where m
alt
and x
alt
are empty weight and CG prior to the modification, x
neu
the target for CG at
empty weight and x
Ballast
the arm of the ballast weight (in front or aft of RP). It must be observed,
that the maximum weight which can be installed at the rear web of the vertical fin is structurally
limited to 2.7 kg / 5.95 lb.
This procedure may be used also to position the CG for good soaring performance with high cockpit
payload. Following this a higher minimum cockpit load must be taken into account.