Survivability of helicopter with individual blade primary control failure

Abstract

The effect of actuator damage on a helicopter rotor with an IBC based primary control system is studied. Such a system eliminates the swashplate and can be accomplished by trailing-edge flaps, active twist or full authority IBC, especially with smart material actuators. Damage to the collective, longitudinal and lateral cyclic are simulated for one blade, both individually and in combinations ranging from partial damage to complete failure. Numerical results are obtained using a dissimilar blade aeroelastic analysis based on finite elements in space and time for hover and forward speed conditions. It is found that the helicopter can be trimmed for all cases with all three controls having failed on the blade with actuator damage thereby showing that the IBC actuated rotor can survive an actuator failure and can be reconfigured by the pilot using the controls on the other blades. However, in case the collective fails and the longitudinal cyclic is present, there are problems in achieving trim at high damage levels at high forward speeds. Physical explanations of this phenomenon are given. The response (especially flap) for the damaged rotor blades can become high and 1/rev and 2/rev are transmitted by the reconfigured rotor to the hub. Results show that IBC based primary controls provide redundancy which can improve the survivability of a helicopter in case of actuator failure in one blade.

An experimental and numerical study of piezoceramic actuator hysteresis in helicopter active vibration control

“…Pilot controls for the main rotor go through a heavy and complicated device called the swashplate. A 1/rev control input given to TEF is known to be an effective solution for a swashplateless torsionally soft rotor 31,32 at high and low advance ratios. Figure 6 shows the hysteresis curves for the PEA for frequencies varying from 5 Hz to 9 Hz.…”

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“…Otherwise, the actuation needed by the IBC system becomes too large. Ganguli et al (2007b) also investigated the optimal placement of helicopter center of gravity to help the swashplateless rotor concept. A parametric study-based optimization approach was used to find the center of gravity location which drove the longitudinal and lateral cyclic to zero in a given flight condition.…”

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“…Without the kinetic restrictions of the swashplate it is possible to decouple the cyclic control inputs between different blades. Thus, the primary control functions can be reconfigured after local failures (partial blade damage or single blade actuator degradation) [16,19]. For this reason, the blade pitch control method is used in the current study with the hopes of examining the effects of IBC on fault-tolerant controls.…”