Low-cost Chelton system emerges from NASA research programme and will start experimental testing next month

Chelton Flight Systems is poised to offer a low-cost autopilot/stability augmentation system (SAS) for light helicopters early next year. Boise, Idaho-based Chelton says it has been working with the US Federal Aviation Administration for two years to prepare the SAS for certification on the Robinson R44 in the second quarter of 2007.

The system will be available for retrofit, and in due course in new aircraft. Chelton says it also expects FAA approval for the SAS on the Bell 206/407 and Eurocopter AS350/AS355 soon afterwards.

Dubbed HeliSAS, the system is a full-authority, dual-processor, fail-passive digital autopilot, product of a NASA research programme for the US Army led by helicopter test pilot and control systems expert Roger Hoh. Chelton, part of the UK-based Cobham Avionics & Surveillance group, says it is manufacturing the system for retrofit or as installed equipment for "any hydraulically controlled helicopter".

The manufacturer says the SAS weighs 5.5kg (12.1lb) and can be fitted in 40h, overcoming the weight problem that has prevented fitment of autopilots or stability augmentation systems to light helicopters.

"We are very pleased with the progress of our development programme," says Hoh. "The autopilot incorporates GPS steering and will track VOR courses or an instrument landing system to minimums. The Attitude-Command-Attitude-Hold SAS greatly facilitates low-speed and hover operations, especially in severely-degraded visibility and in winds and turbulence. Hands-off hover is possible, and demonstrations in test aircraft have shown that the SAS allows fixed-wing pilots with no helicopter experience to take-off, hover, perform pedal turns and land."

In normal manual flying, the HeliSAS can turn the R44 from a sensitive machine with very light control forces into one that feels like a larger, more stable helicopter, according to test pilots.

Chelton says it has already done 230h test flying with HeliSAS in the R44, and expects to start environmental testing in late November. "We would like to announce the [type certification] approval at the Helicopter Association International Heli-Expo in March next year and are on schedule to achieve this," the company says.

It is aiming for the end of 2007 for approval in the Bell 206 and Eurocopter EC120 by late 2007, and in the Bell 407 and Eurocopter AS350/AS355 the following year, says Chelton. It has not released a unit price yet.

Source: Flight International