The active compensation concept of crankshaft assembly generated dynamic loads for aeroplane boxer engine

Piston engine, by its cyclic nature, generates important dynamic solicitations of aeroplane structure, avionics and passengers. After carrying-out design and manufacture balancing procedures there remains, especially for low-cylinder-number engines, non-equilibred forces and mostly - reaction torque, consisting of several harmonics of significant amplitudes. The aeroplane structure designer traditionally tries to cope up with those loads with rubber mounts. As they act in a passive way and can be effective only in a specific frequency scope, their application is immanently linked with compromises concerning mounts stiffness, damping and consecutively - degree of vibroisolation. During last decennies, a new trend is developing in automotive and similar branches -the active vibroisolation. Described investigations concern application of this concept to aero-engine piston suspension. Dynamie model was verified by comparison with measurements of vibrations of Frankiin-4 engine suspended on Koliber light aeroplane. Semi-active approach was first checked up - natural frequencies were "adapted" to varying engine's RPM. Then few physical values were used to compensate engine vibration in closed loop. Both dynamic schemes proved to be highly effective, giving way to appropriate prototype implementation.