Maintenance Manual STEMME S10-VT
Date of Issue: Jan. 01, 1998
Page 6-3
Amendment Nr. 0
Date: --
A4011121_B23.doc
Doc. No. A40-11-121
Following an a/c repair, painting or modification of equipment, it always must be checked, if 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 (Annex D). Formula:
x
m
x
m
x
m
x
m
neu
alt
alt
zus
zus
zus
zus
neu
1
1
2
2
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 ref. to Datum
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 table 6.3.
CAUTION:
Basically the arms of weights in front of the Datum must be counted negative, those aft of the
Datum positive for any calculations.
If the effect of a modification or repair cannot be calculated (e. g. when having painted or following a repair of
the composite-structure) the a/c 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
m
x
x
x
x
Ballast
alt
neu
alt
Ballast
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 lbs.
This procedure may be used also to position the CG for good soaring performance at high payload in the
cockpit. Following this a higher minimum cockpit load must be taken into account and a reinforcement of the
rear web of the vertical fin may be required.
If a revision proved the a/c to be "tail-
heavy“, the minimum load m
P, min
for an unchanged empty weight m
leer
and CG position x
leer
can alternatively be determined by following formula:
m
m
x
x
x
x
P
leer
leer
flug h
flug h
P h
,min
,
,
,
with:
most aft in-flight CG:
x
flug,h
= 420 mm
/
16.54 in
(aft of Datum)
most aft seating (CG) position of pilot:
x
P,h
= - 545 mm
/
21.46 in
(in front of Datum)
The certified limits of the empty weight CG as a function of minimum load can be derived from the following
table. If maximum or minimum loads for the different compartments and seats are observed and the empty
weight CG is within limits, the in-flight a/c CG is always within certified limits. This means, that the load in the
seats must be higher than or equal the minimum load, whereas total cockpit load (pilot + co-pilot +
para baggage) must be below the specified maximum load.
The difference of total cockpit load and the maximum load must at least allow for a fuel load required
for a 30 minutes flight at maximum continuos power (13.6 l / 3.6 US gal / 3 imp.gal, 10 kg / 22 lbs.).
