Change Modelling Case Studies

Change prediction for an EH101 helicopter

Many industries, such as the automotive industry, are working on modular designs, with clearly defined interfaces between subsystems to reduce the complexity of their products and facilitate the reuse of sub-systems across a product range. The subject of the case study reported in this paper is particularly complex: a helicopter.

The systems of a helicopter are highly interconnected through functional parameters such as balance and vibration, while being minimized for weight. In comparison to other products, military helicopters are produced in very low volumes. Often fewer then 30 identical sub-systems are required which in turn have to be supported throughout the entire 30-year life span of the craft. Over the past 15 years Westland Helicopters have been developing the EH101, a civil and military sea rescue and attack helicopter.

They describe the EH101 as a ‘‘new concept’’ - ‘‘Based on a common airframe and core systems, the EH101 is configured to meet the multi-role requirements of many diverse customers around the world. It is uniquely capable of mastering the requirements of any role using the same airframe and core systems’’. Thus, the basic design is partially redesigned for each new customer. Even with this philosophy a fully modular helicopter design could not be achieved at reasonable cost and each new version requires considerable development effort.

Westland Helicopters originally approached the authors in response to earlier work involving the capture of complex design processes. They wished to develop a tool to support the management of design changes to existing helicopters. This led to an empirical study in order to analyse the change execution processes in Westland Helicopters. The study consisted of interviews, group knowledge acquisition exercises and the collection of specific redesign examples. These led to the development of the Change Prediction Method.

The EH101 example can be downloaded here: EH101-CPM.cam