ALLIEDSIGNAL AEROSPACE is developing a helicopter version of its Mark VII ground-proximity warning system. The Mark VII has been marketed since 1990, for fixed wing aircraft equipped with ARINC 500 analogue avionics and AlliedSignal began a year-long testing programme, for the system on an Era Aviation Bell 212, in November 1995.

The AlliedSignal system has also been tested on a Sikorsky SH-3 helicopter since 1991. In its fixed-wing version, the Mark VII is being used on more than 500 military and 2,500 commercial transports, including heavy jet-powered and business aircraft.

According to Steve Barkley, engineering manager for flight-safety avionics, AlliedSignal Aerospace Commercial Avionics Systems, the Mark VII software will have the same terrain-monitoring capability as that of the fixed-wing version. For helicopters, it is being configured to monitor engine torque and to recognise commencement of auto-rotation.

"In an auto-rotation mode, the helicopter has lost power, so the pilot must make a controlled descent to minimise damage. To do this, the Mark VII will synthesise altitude call-outs instead of the usual 'pull-up' warning during auto-rotation," Barkley says.

He adds, that provisions for "flare call-out", will also be available for auto-rotation situations.

In addition, the Mark VII will be used to monitor pitch rate. "If the pitch rate is too high, the pilot will get an aural warning, and prevent a possible tail strike," Barkley says. "We are also making provisions for slung- or hook-load ground-strike provisions. For helicopters with retractable landing gear, a gear-down alert can be added."

Barkley points out that AlliedSignal is expecting to certificate the Mark VII version this year under a US Federal Aviation Administration technical-standards order. The system's initial production application is expected to be for the Sikorsky S-76 civil helicopter.

Source: Flight International