Gulfstream testing fly-by-light controls

 - April 1, 2008, 7:09 AM

Just days after taking the wraps off the fly-by-wire G650 last month, Gulfstream revealed that it has successfully flown a GV testbed fitted with a fiber-optic “fly by light” (FBL) control system.

The FBL technology that is being demonstrated on the testbed is actually a generation beyond the fly-by-wire (FBW) system developed for the G650, Gulfstream said. Fly-by-light control systems use fiber-optic links instead of wires to transmit data from the flight control computers to the actuator control electronics. Besides being lighter, fiber-optic cables can transmit several channels of bidirectional information simultaneously.

During the inaugural 75-minute flight with the Gulfstream FBL system, a fiber-optic harness transferred pilot control input from a flight control computer to spoilers on the wing. According to Gulfstream, the FBL technology provides a “significant” weight saving over fly-by-wire systems by streamlining a “bulky wire bundle into just four fiber-optic cables.”

The FBL system also enhances safety, Gulfstream said, by transmitting a redundant signal, an inherent feature of the fiber-optic system that would require a second wire bundle for a FBW system to match. So far, the FBL testbed has made two flights and logged 1.8 hours aloft. A Gulfstream spokesman said the FBL system could be commercially available in less than 10 years.

Fly-by-light, if perfected, would surpass fly-by-wire because of its immunity to electromagnetic interference, lighter weight and broader transmission spectrum, experts say. The latest generation of fighter aircraft, including the Eurofighter Typhoon, uses fiber-optic control links.

In January 2002 a modified Eurocopter EC 135 flew with a fly-by-light primary control system. The helicopter, designated Active Control Technology demonstrator/flying helicopter simulator (ACT/FHS), is under development by Eurocopter and Liebherr Aerospace in cooperation with the DLR aerospace research center in Germany and the German Armed Forces test center. Optical flight control systems would enhance helicopter controllability and stability in windy conditions,
developers say.