There is general agreement that fly-by-wire (FBW) is the control system of choice for most new aircraft, military or commercial, but there is less unanimity about sidesticks. Airbus uses them; Boeing does not, not even—so far—in its military aircraft.

But the list of manufacturers yet to embrace the sidestick is growing shorter. Bombardier selected them for its CSeries airliner and has switched to FBW and sidesticks for its new Global 7000 and 8000 business jets. Dassault, Embraer, Bell, Sikorsky, Comac, Irkut and Sukhoi are all adoptees.

The principal reason for using sidesticks is ergonomics. Removing the control yokes allows for larger flight displays and—in the latest cockpits—pilots can be moved closer to the instrument panels, allowing use of touchscreens. The biggest drawback of the “passive” sidesticks now used in civil aircraft is the lack of control feedback from the aircraft or the other pilot.

But the transfer of “active inceptor” technology to the commercial sector from the military is helping to overcome that objection. Active sidesticks that provide tactile and visual feedback in response to pilot and autopilot commands are used in the Lockheed Martin F-35 Joint Strike Fighter and Sikorsky CH-53K heavy-lift helicopter. Now Gulfstream is the first civil manufacturer to adopt active sidesticks, for its new G500 and G600 business jets.

In 2010, BAE Systems was selected to supply sidesticks for the G500/G600. The company has developed the active inceptors for the F-35 and Korea Aerospace Industries T-50, as well as the CH-53K and Sikorsky’s fly-by-wire UH-60M upgrade. But the military technology could not be ported directly over to the commercial market because of the certification requirements, says Adam Taylor, director of active inceptor programs.

BAE has developed a commercial active sidestick with its own investment. Gulfstream was the launch customer, but the same device was selected by Embraer for its KC-390 tanker/transport. Where the military systems have triplex redundancy, the commercial version is dual-duplex, using dissimilar processors so there are no common failure modes between channels. Sidestick force and position-sensing is quadruplex redundant to meet certification requirements.

All of the hardware and software are packaged within a single line-replaceable unit that interfaces with the aircraft’s flight control computers, while dedicated electrical links connect the pilot and copilot inceptors. This ensures both sidesticks move together in response to both pilot and autopilot commands, providing crew situational awareness equivalent to conventional pilot controls, says BAE.

Sidestick characteristics—breakout forces, force displacement gradients and soft stops in each axis—are programmable and can be tailored by the aircraft manufacturer. “We offer an active stick with a feature toolbox that provides a wide range of parameters that can be tailored,” says Taylor. These include the breakout forces required to move the sidestick from its null position, “so the pilot has to pull, say, half a pound before it starts to move, to prevent inadvertent inputs and provide an obvious centering feel,” he says.

Soft stops are vertical sections of the force displacement gradient that provide tactile feedback on aircraft limits. “These are miniature walls that move back and forward and cue the pilot to impending limits. At 10 deg., the pilot may have to put in an extra 5 lb. of force to get over a mini wall,” says Taylor. While a stick-shaker function “comes for free” because of the servos inside the unit, the stall-prevention stick-pusher function of conventional controls is replaced by soft stops that guide the pilot, he says.

But the biggest advantage claimed for active over passive sidesticks is that both pilot and copilot controls track each other at all times. “This provides good situational awareness between the pilots—they can both see and feel their sidesticks moving,” says Taylor. If the aircraft manufacturer wants it, a jammed controls mode can be implemented so the pilot can continue to fly the aircraft using the active sidestick’s force-sensing capability, he says.

Embraer’s KC-390 is expected to fly first with BAE’s commercial active sidesticks early this year, followed by Gulfstream’s G500. The KC-390 is scheduled to enter service in 2016, followed by the G500 in 2018 and the G600 in 2019. “There is a lot of interest and we are expecting other platforms to move forward with active sidesticks,” says Taylor. “Manufacturers are moving toward sidesticks for ergonomic reasons, but the linking and tactile cueing provided by active inceptors give extra situational awareness.”

Other suppliers are developing similar systems. France’s Sagem displayed a prototype of its active sidestick for civil aircraft and helicopters at the National Business Aviation Association show in October, and Liebherr active inceptors have flown on a research helicopter in Germany.

Editor's note: An earlier version of this story provided incorrect expected service-entry dates for the G500 and G600.

 

A version of this article appears in the February 2-15, 2015 issue of Aviation Week & Space Technology.