Equipment manufacturer Sagem, which is developing the fly-by-wire (FBW) controls that will be installed on the Eurocopter X4 medium twin, is pledging they will improve safety, reduce pilot workload and enhance flying precision. Although fixed-wing aircraft have used FBW for decades, integrating the system on a helicopter is more complicated.
The move to FBW begins with “cutting the direct link between the pilot’s body and the aircraft’s control surfaces,” Guillaume Thin, Sagem’s v-p in charge of “future helicopter program,” told AIN.
With a FBW system, “the aircraft no longer needs detailed orders, as it does a lot by itself,” said Thin. “A computer interprets the pilot’s orders and determines the optimal order to send to the control surfaces,” he added. Sagem produces the FBW system of the NH90, a 24,000-pound military transport helicopter that is already in service. The company is incorporating its experience with this program as well as recent progress in on-board computers into the X4 “future helicopter program” application.
Reliability, computing power and compactness of the system has improved since initial applications. More critically, these computers need less electric power, making it possible to design a FBW system for a helicopter in the 11,000-pound class.
Introduction of the FBW system will make flying a helicopter simpler, according to Thin. First, the system will reduce the number of controls the crew uses, as “innovative” sidesticks will regroup several functions and the interface will include touchscreen displays.
Another benefit of a FBW system is flight envelope protection, both from an aerodynamic and propulsion standpoint, Thin emphasized. The result is a reduction in pilot workload, as the pilot no longer has to think about these safety margins. In addition, the company expects better precision, since the computer determines the right movement for the control surface, even though the environment is changing. For example, the computer understands the pilot’s input and finds a way for the helicopter to respond accordingly, regardless of turbulence.
As the system simplifies flying, training should also become more straightforward, according to Thin. “You are using high-level parameters such as heading, speed and climb rate, as opposed to low-level ones such as control surface angles,” he said.
A challenge, Thin added, will be integrating the FBW controls with the navigation system.
Eurocopter has planned two versions of the X4, one for 2016, with a more advanced one to follow in 2020 (see AIN, August, page 52). Sagem believes its FBW system can be ready in 2018. Eventually, actuators will be electric, too (as opposed to hydraulic). The first in line are the tailrotor's pitch actuators.
Sagem is also developing new optronics to give the pilot a broad picture of the situation, combining traffic, weather, terrain and obstacle information.
