FARNBOROUGH: Bell, CMC build better velocity sensor

Bell Helicopter from next year will offer an enhanced automated approach-to-hover and hover-hold capability for the Bell 412EP and other models as part of a development project with CMC Electronics.

The low-cost sensor centres on improvements to the velocity measurements traditionally provided by a traditional Doppler sensor or GPS unit and used by a helicopter's autopilot to accurately follow an autonomous approach and hover.

Rather than deriving velocity directly from a GPS sensor or Doppler system, the companies' ground velocity sensor processes "a specific property of the raw GPS signals to produce an actual velocity versus reporting changes in GPS positions over time", says Bell. While computing velocity by comparing sequential GPS position readings is valid, the new process provides a smoother more accurate result.

"The CMC GPS solution proved more responsive in flight tests than both the legacy Doppler and any of the GPS-aided solutions being examined tied to the existing 412EP autopilot," says Nick Lappos, Bell's chief technology officer. "We see this technology and the capability it brings as a means to improve safety in low-speed operations in general as well as reduce the cost of [search and rescue] operations."

Bell says the ground velocity sensor, which was developed as a standalone software upgrade to the CMC CMA-5025 GPS receiver, is not dependent on satellite-provided GPS augmentation and is therefore usable worldwide.