Gulfstream test pilots & flight-test engineers recently made business-aviation history when they flew the Gulfstream G650 flight-test aircraft for the first time using only an electrically powered, fly-by-wire back-up flight control actuation system.
Gulfstream’s Serial Number (S/N) 6001 flew for a total of 3hrs & 33 minutes on 21st December 2010. Test pilots Jake Howard and Gary Freeman along with flight-test engineers Bill Osborne & Nathaniel Rutland evaluated the fly-by-wire system in electric back-up actuation mode for 2hrs & 20 minutes of the flight, performing five landings with the backup system engaged.
“The system performed flawlessly” said Pres Henne, senior vice president, programs, engineering & test, Gulfstream. “There was no difference in handling qualities between the electrically and hydraulically powered modes”
“It flew so well that unless pilots were told they were in the back-up actuation mode I don’t think they would notice” said test pilot Freeman.
Typically, fly-by-wire uses a third hyraulic system to provide redundancy in the event of a dual hydraulic system failure. However, Gulfstream’s fly-by-wire architecture uses electric back-up hydraulic actuators (EBHA): electronically controlled actuators that are primarily hydraulically powered but offer electric power as a back-up.
The G650 has an EBHA at every primary control surface (elevator, rudder & aileron) as well as the outboard spoiler. These Provide enhanced safety & aircraft availability because of the two different power sources. The self contained actuators also offer an advantage following extremely rare failure scenarios, such as a rotor bust.
The 21st December G650 flight began with evaluating the electric back-up mode handling qualities in one axis and then progressed to full evaluations in all axes (pitch, roll & yaw). The test conditions consisted of all flap settings at 10,000 feet for speeds ranging from.13 reference stall speed (VSR) to maximum flap extended speed (VFE). Cruise configurations were evaluated at FL280, FL350 & FL450 and the full speed spectrum. The pilots also initiated an emergency decent profile from FL450 to FL250. Additionally, they evaluated handling qualities in the landing configuration by making multiple offset approaches at Brunswick Golden Isles Airport in Brunswick, GA.
