Maintenance Manual LS8
Issued: December 2009
Copyright DG Flugzeugbau GmbH - any copy or publishing prohibited
Manual valid with the up-to-date cover page only
2-1
2 Mass and balance
2.1 Weighing procedure
Datum Line <DL>: Under side of fuselage boom placed horizontally
Datum Point <DP>: Leading edge of wing at root
1. Determine total mass (Empty or take-off mass) for both wing span
versions, in most cases by weighing all parts and adding together. When a
tail fin battery is being used, weighing must always be done with tail
fin battery installed. Weigh mass of tail fin battery separately
(3BR-199, 2.5 to 2.7 kg; <5.5 to 6 lbs>). For details see under Calculation
of Loading Limits.
2. Assemble the sailplane in the 15 m version. For in-flight C.G. position,
the pilot must be seated in the sailplane.
3. Raise tail on weighing machine until datum line is level using wooden
blocks or adjustable rack. Check with levelling gauge.
4. Measure distance <b> from tail support to centre of landing gear axis.
5. Using plumb lead, determine points on floor perpendicular to left and right
datum points, and points on floor perpendicular to centre of landing gear
axis. Measure distance <a> from wheel axis to datum point.
6. Determine tail mass and deduct mass of auxiliary support used under 3) to
get net tail mass.
7. Calculate C.G. position for empty vertical tail fin tank:
net tail mass * b
Xcg = + a
total mass
8. Calculate C.G. position for full vertical tail fin tank:
(net tail mass + tail fin water mass) * b
Xcg = + a
total mass + tail fin water mass
9. Calculate loading limits according to section 2.2.
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