OVERVIEW OF THE EC155 DYNAMICS VALIDATION PROGRAM FROM DESIGN STAGE UP TO CERTIFICATION

EC 155 is a multimission 5-ton helicopter developed by EUROCOPTER for the civil and military market. EC 155 has been certified and delivered to the first customer at the end of 1998. This paper gives an overview of the dynamics validation program that was applied during EC 155 development from the design stage up to the certification. It summarizes various aspects of rotor dynamics, vibration control, aeroelastic stability and response characteristics by comparing component and shake tests with theoretical results derived from calculation programs. These activities are part of the general EC 155 dynamics validation program. Aspects of the main and tail rotor layout are discussed and investigations regarding blade tuning, aeroelastic and aeromechanical stability are addressed. The identification of the rotor modes tested on a whirl tower is described and a comparison is made between theoretical values and measurement. The drive train was designed without any major modification and the dynamic model helped analyze the torsion dynamics of the whole drive train system. The non-linear engine characteristics provided by Turbomeca were linearized about a steady condition. The stability margins were derived from standard open loop Bode plots. This theoretical work is presented with flight tests used as validations. The EC 155 shake tests are presented. These tests were intended to identify the frequencies, mode shapes, modal damping and generalized masses of the fuselage on the ground. The fuselage natural frequencies and modes as identified during the shake tests have been correlated with the results drawn from the finite element model. Although it is not fitted with an anti-vibration system, EC155 shows an excellent vibration level lower than 0.1 g at 5/Rev over a speed range up to 150 kt. The flight test data are presented.