Automatic Flight Control System Design for S-64 Helicopter
Erickson Air-Crane has over 20 heavy lift Sikorsky S-64 helicopters manufactured over 30 years ago. This helicopter had an Automatic Flight Control System (AFCS) with complex, low reliability electro-mechanical gyro inputs, obsolete electronics, and inconsistent flight performance. Sikorsky no longer supported the AFCS system and used spare parts had been depleted.
Stilwell Baker was approached by Erickson Air-Crane (EAC) to design, engineer, and implement a new autopilot system. Stilwell Baker partnered with EAC, and utilizing modern electronic components, solid-state Air Data Attitude Heading Reference System (ADAHRS) inputs, and reduced electrical components/connections, completed the AFCS in record time.
This was a demanding avionics engineering project, as the schedule required the system to be certified in 18 months, half of the time any similar project had been certified previously by the FAA. A significant portion of the original system documentation did not exist and many items had to be reverse engineered. The system had to meet DO-160F certification requirements including lighting and High Energy Radio Frequency (HERF) susceptibility, severe environmental and vibration specifications, requiring significant aircraft flight-testing.
The EAC S-64 project required complete engineering system documentation and FAA avionics certification for the completed system design.
Stilwell Baker completed the project on the aggressive schedule, and the new system successfully passed First Article Acceptance Testing with all polarities, gains, and functions correct on the first pass.
The redesign resulted in a reliable, supportable autopilot system, with 50% increased reliability, 33% reduction in system weight, improved aircraft stability, and readily available parts support.