The CH-47F CAAS-DAFCS Coupled Flight Director

Initial CH-47F Digital AFCS development and flight testing focused on advanced lowspeed modes (ACAH, TRC, PH and altitude hold) for enhanced capability and safety when hovering in poor visibility. Following successful fielding of the advanced lowspeed modes, a program immediately ensued to improve the coupled Flight Director (autopilot) performance beyond what was possible with the legacy analog AFCS. These improvements were realized with only software changes. Using a systems-engineering approach, the Boeing and Rockwell Collins design team worked with the U.S. Army customer to define and prioritize new system requirements. Solutions to all the requirements were developed using a high-fidelity integration lab, allowing a compressed program schedule of 8 months from program start to first flight while simultaneously minimizing developmental flight test time. The U.S. Army Aviation Technical Test Center conducted the developmental flight testing with on-site support from both Boeing and Rockwell Collins. The redesigned autopilot exhibited excellent performance in flight test. Workload reduction was measured quantitatively using the Subjective Workload Analysis Technique (SWAT). Coupling the Flight Director to the Digital AFCS was shown to greatly reduce cockpit workload, which not only reduces pilot fatigue on long missions but also frees pilot capacity to focus on mission objectives and evolving threats. By pairing advanced lowspeed modes with the coupled Flight Director, the CH-47F enhances capability and reduces pilot workload in all flight regimes. This paper describes the CH-47F coupled Flight Director development process, some highlights of the system design, its advanced capabilities, and presents flight test results.