Vibration rating of medical helicopters

Helicopter Emergency and Medical Service (HEMS) requires a specially designed cabin interior that can transport patients quickly to a full capacity hospital. During the transportation, a medical crew sustains the health condition of the patients using life-support equipments, hence the quality and safety of the service may depend on the vibratory level experienced by patients and crew. However, the bare dynamical response of the airframe can lead to erroneous evaluation of vibratory level and exposure. In fact crew, patients and medical equipments, ı.e. subjects of HEMS, dynamically interact with the helicopter through interfaces such as seats, handles, stretchers and flexible supports. For this reason, the design of a low vibration HEMS vehicle requires numerical analysis of the coupled helicopter-interface-subject system, and the capability to effectively and efficiently run the analysis for a large set of possible configurations to achieve optimal positioning. A viable tool should be able to formulate high-fidelity rotorcraft aeroservoelasticity, easily connect additional dynamical systems representing the dynamics of human and equipment and their interfaces, and calculate the vibration performance of the resulting models. This work presents an effective way of evaluating the vibratory performance of medical helicopters. The approach is illustrated on a medium weight helicopter by adding dynamical models of a human resting on a seat, a recumbent person lying on a stretcher, and medical equipment mounted on flexible supports at its ends.