As part of the Norwegian Search and Rescue contract for the AW101 Leonardo helicopters were contracted to conduct a Performance Improvement Programme.  This Programme employed a Joint Test Team construct with the Norwegian customer to develop the core cockpit HMI for the new power ratings.  NDMA test pilots worked with the company to develop the new HMI through a series of activities leading to the implementation of the upgrade which reduced the flight testing required to the absolute minimum and a rapid entry to service.  This lecture will explain the details of this joint approach and provide lessons for future HMI development programmes.