In a bid to expand the performance envelope of its CH-47F and MH-47G Chinook heavy-lift helicopters, Boeing has called on BAE Systems electronics engineers to develop a retrofittable active-feedback control stick system.

A so-called active parallel actuator subsystem (APAS) should give Chinooks many of the benefits of fly-by-wire control without the expense, and re-certification complications, that would come with developing a FBW system for these in-production aircraft.

Like pilots of other non-FBW aircraft, Chinook pilots are guided to the limits of the flight envelope by soft stops that are set to a single position. But an APAS system will replace those fixed, mechanical stops with dynamic, electronically generated stops that will be adjusted to actual flight conditions - and thus allow pilots to pull more performance out of their aircraft without fear of overstressing the airframe.

And, says BAE advanced inceptors director Adam Taylor, the APAS system will give pilots a range of tactile warning signals through the control sticks - a feature familiar to pilots of FBW aircraft such as the Eurofighter Typhoon and Lockheed Martin F-35, which are fitted with BAE's active inceptor system sidesticks. Taylor describes the overall objective as "80 per cent of the benefits at 20 per cent of the cost".

In the Chinook, an APAS unit will replace the box of springs and dampers that currently sits between the control sticks and the BAE-produced system that drives the flight control surfaces.

APAS is scheduled for flight testing in early 2015, with production starting in 2018.

Source: Flight International