The Modelling, Simulation and Control of Helicopters Operating with External Loads

The concept of using helicopters to carry loads externally is almost as old as the helicopter itself and is now commonplace, with applications both in civil and military environments. Essentially, the external load behaves like a pendulum, changing the natural frequencies and modal shapes of the helicopter’s low frequency modes. The external load introduces three main effects to the dynamics of the system. These include:

  • Additional pendulum-like rigid body modes associated with the swinging of the load.
  • Load aerodynamics.
  • Sling stretching.

These effects degrade the helicopter stability and handling qualities, reducing the operational flight envelope of the slung-load system to below that of a single helicopter with no load. Control schemes that stabilise the external load, reduce pilot workload and ensure safe flight across a wide flight envelope would clearly be beneficial. With safety in mind, simulation can play a major role in the design of such control schemes and this is a key motivator in the present project. The project aims to investigate the stability and dynamics of helicopter slung load operations.


  1. Kendrick, S. A. and Walker, D. J., "The Modelling Simulation and Control of Helicopters Operating With External Loads," presented at The 62nd American Helicopter Society Annual Forum, Phoenix, Arizona, USA, 2006.