1. The flutter analysis of the JS1 glider
Pieter S. Rossouw
Master’s Degree Student
Supervisor: Mr. Attie S. Jonker
North-West University (Potchefstroom)

2. Introduction New composite glider: JS1 Revelation 18 meter wingspan
Maximum speed:
290 km/h (Vne)
Designed by Attie Jonker
& team
Certify new aircraft
Design diving speed (VD)
1.2VD = km/h
= knots
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3. Problem definition/statement
What is flutter?
Flutter analysis main steps
Modal analysis
Flutter prediction
Flutter flight test
Modal analysis done by
Finite element software
Ground vibration test
JS1 flutter analysis steps:
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4. Modal analysis Ground vibration test @ CSIR Two glider configurations
Simulate free condition
Excitation with electrodynamic shaker
Response measurement with sensors
Dynamic characteristics are
Natural frequency
Mode shape
Modal damping
What is a mode?
Wing, fin and tailplane modes found
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5. Modal analysis (continued)
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6. Modal analysis (continued)
2nd symmetric wing bending @ Hz
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7. Flutter prediction Use modal data in flutter code
Flutter code utilizes
Doublet lattice method
p-k method
Flutter results
Damping vs. airspeed
Frequency vs. airspeed
Altitudes up to 8000 meters
One indication of flutter: 430 knots
Results above 210 knots – no concern
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8. Flutter prediction (continued)
210 knots
(1.2VD)
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9. Conclusion Modal analysis done by Flutter analysis done for
Ground vibration test
Flutter analysis done for
Speeds up to km/h
(210 knots)
Altitudes up to 8000 meters
For all modes found
Stability for
JS1 design envelope
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