THE US FEDERAL Aviation Administration has completed a four-site test programme to develop standards for helicopter non-precision-approaches, using global positioning (GPS).

A GPS-based approach was demonstrated at Heli-Expo using a Eurocopter BK.117 equipped with an AlliedSignal Bendix/King KLN-90B GPS and Arnav Systems datalink.

Steve Hickok, helicopter GPS projects manager at the FAA, says that GPS approaches have been implemented at four sites as a result of the industry-supported test programme, which was intended to develop standards for the design of stand-alone GPS approaches.

Involved were the Erlanger Life Force at Chattanooga, Tennessee, using a Bell 412 equipped with a Garmin GPS and Arnav datalink; Petroleum Helicopters at Morgan City, Louisiana, with the same 412/Garmin/Arnav combination; the University of Wisconsin at Madison, with a Corporate Jets Eurocopter AS.365, equipped with a Trimble GPS; and the Mayo Clinic at Rochester, Minnesota, with a BK.117 equipped with an AlliedSignal GPS.

Hickok says that the standards for helicopter GPS non-precision approaches are expected to be published in June.

Results of the test programme are "very good", he says, adding that data from the 200 tracked approaches flown in "obstacle-rich environments" are "very accurate", showing no measurable navigation-sensor error even with accuracy-degrading selective availability on the GPS signal.

The accuracy possible with the GPS will reduce the separation needed between approach paths and obstacles such as buildings, compared with a conventional instrument approach, he says. This will make designing non-precision approaches for helicopters easier, as shown by the Heli-Expo demonstration.

Design of the approach to the car park at the Las Vegas convention centre was only begun in December, Hickok notes.

The Heli-Expo exercise also demonstrated helicopter automatic dependent-surveillance. The BK.117's GPS position was transmitted by datalink for display, in real time, at the Arnav exhibition stand and the nearby McCarran Airport control tower.

Source: Flight International