21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-4.5.3

N-2S0 PROTOTYPE 1 FLIGHT FLUTTER TESTING DEVELOPMENT

Risdaya Fadil M., Indrawanto, Djojodihardjo H.*
Indonesia Aircraft Industry Ltd., Indonesia; *Agency for the Assessment and Application of Technology, Indonesia

Keywords: n-2s0 prototype, flutter, testing, development

Modern Flight Flutter Testing of aircraft requires application of artificial excitation. This paper presents the development of N250 Prototype-l Flight Flutter Testing using an aerodynamic vane. An important consideration in aircraft Flight Flutter Test is the use of controllable aerodynamics vanes to generate a well defined shaking force. The force has to be high enough to excite the aircraft structure beyond its normal flight vibration level The response of the aircraft structure to the exciting force is analyzed to determine the vibrational stability parameters. The best exciter locations are chosen to excite the symmetrical and anti-symmetrical bending and torsion modes of the lifting surface beyond its normal flight vibration level Sine-sweep and sine dwell excitation types yield higher structural response levels as compared to random or impulse step excitation. The former is less complicated to analyze. The instrumentation to measure the vane forces and responses are located at positions where the aircraft responds best to the excitation. The flight test procedure starts with test points from a safe initial condition and proceeds with small speed increments up to the ultimate speed, Mach condition, VDIMD' Theoretical predictions in combination with the resonance frequencies and the corresponding damping and transmissibility factors, as a function of speed, provide an estimation of the critical speed beyond which vibrational instability can occur. The paper concludes that the vane, developed by Dynamic Engineering Inc. (DEI), is easily operated for in-flight excitation. Flight Flutter Testing of the aircraft is accomplished in a quick, accurate and safe way. Higher excitation frequencies are reached than were possible with stick raps.

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