Pilots take control of the CSeries flight deck
With a clean sheet and no drag from concerns about commonality with an existing fleet, was able to enlist its pilots, engineers, customers and supplier base to come up with a fresh new environment for the flight deck of the , the company's largest aircraft to date and its first fully fly-by-wire design.
It remains to be seen how airline pilots will respond to the new design when deliveries of the CS100 begin in 2015, but a recent “flight” in the company's engineering simulator reveals a cockpit designed specifically with them in mind.
“The whole philosophy was to make massive big windows for the pilot looking outside, heads-up,” Mark Elliott, Bombardier CSeries liaison pilot, tells Aviation Week. Bombardier provided Aviation Week 1 hr. in the CAE-built engineering simulator for the type last month, accompanied by Elliott in the right seat and Robert Dewar, the CSeries vice president and general manager, in the back. Elliott, a former airline pilot flyingand , is a liaison for customers with fleets; a colleague with airline experience flying aircraft focuses on those with Airbus fleets.
“Pilots were brought on very early in the program in terms of what pilots want,” he says. From a pilot perspective, the aircraft would be intuitive to fly; from a performance perspective, it would deliver relatively short takeoffs and landings, steep approach capability for fields such as, and have the ability to operate at airports as high as 14,000 ft. Those needs drove certain aspects of the design, including the fly-by-wire (FBW) approach and five settings for the flap system—three to be used for takeoff and two for landing.
The spaciousness of the big-window cockpit is more than an illusion. By using double-curvature windscreens built by PPG Aerospace, Bombardier was able to make the cockpit taller than similar single-curvature designs. And by removing the control yokes in favor of sidesticks, the pilots could move 6-7 in. closer to the windscreen and displays compared to legacy designs, says Dewar. “Some of the older pilots told us they can be closer to the panel visually to see the switches,” he says.
Pilot seats are mounted on “J” tracks that slide them inward and forward; they are controlled by a mechanical lever and propelled by some old-fashioned scooting on the pilot's part. Looking forward and right from the left seat, the five 15.1-in. displays that are part of theFusion integrated flight deck are within easy, unobstructed view and reach. All screens have the same part number, and airlines can dispatch with one screen out, not including the primary flight displays (PFD). If a screen fails in flight, the information automatically reverts “inwards and downwards” to adjacent screens, says Dewar.
Bombardier considered using touchscreen technologies but chose knob and button controls and center pedestal-mounted track balls instead. “This is far more accurate,” Elliott says of the human-machine interface. “With a track ball, it highlights the field so that I know it's the correct field before I activate it.” The track ball is very intuitive, with the cursor moving seamlessly between displays as you roll the ball with your fingers. Dewar notes that the on-screen menus are one level deep, not cascaded.
On the glareshield are the traditional autoflight system controls on the mode selection panel, but new for the CSeries are the radio-tuning controls that are typically mounted in the center pedestal. “Our philosophy is that you don't want guys [looking down] and tuning. You want them looking up,” says Elliott.
One new guarded switch on the glareshield—labeled “EDM” for emergency descent mode—is a safety aid that came up from Bombardier's business aviation side. The mode can be manually selected, but the system is always armed to automatically descend after a depressurization event or cabin altitude problem, assuming the pilots are incapacitated. Once engaged, the EDM automatically turns on the autopilot, retards the thrust levers to idle, sets an emergency code in the transponder, dives to 15,000 ft. at maximum velocity and levels off. The EDM, which Dewar says is the only CSeries system that automatically takes control of the aircraft, does not provide terrain protection.
When looking up at the overhead panel, pilots will notice a very compact arrangement, with each switch having three settings: off, on and automatic. The automatic setting is in the 12 o'clock position (aligned with the direction of flight). With the switches lined up and no lights on, the pilots are assured that systems are in automatic mode and no faults have been detected, part of a “dark cockpit” philosophy. “Things like hydraulic pumps, anti-ice and batteries will be in auto all of the time,” says Elliott.
The design of the overhead panel resulted from feedback from the airlines “to try and make it simple and intuitive and to lower pilot workload,” says Dewar. It also resulted in an overhead panel three times smaller than Bombardier's overhead panel at the beginning of the program, Dewar says. Behind the overhead panel is an escape hatch for the crew.
In the engineering simulator, the left-side seat is equipped with a Rockwell Collins HGS-6510 drop-down, head-up guidance system, an option available for both sides of the cockpit. Other options include a tiller for the right-seat pilot, right- and left-side Esterline CMC Class 2 electronic flight bags (EFB) and Category 3b instrument landing system capability. Sometime after initial operations other options will be available, including Rockwell Collins's synthetic vision for head-down and head-up displays, as well as enhanced vision systems. Along with the Fusion flight deck, Rockwell Collins provides its MultiScan weather radar and the CSeries primary flight control computer, which executes the control laws behind Bombardier's FBW system.
Preparing for our simulated taxi and takeoff, Elliott describes the pilot controls—left and right FBW sidestick controllers, conventional rudder pedals connecting to a steer-by-wire system for taxi, takeoff and landing, and conventional toe brakes controlling the electric brakes in the brake-by-wire system. The parking brake is an on-off switch at the rear of the center pedestal.
Dewar pointed out that the thrust levers are back-driven in the autothrottle mode, but the left and right sidesticks are not coupled. “Our pilot working group studied that for two years,” he says of the coupled sidesticks. “The complexity of the coupling added more problems than the solution. We looked at mechanical, electrical and hydraulic linkages, and there were no technologies that were reliable that made sense to us.”
The FBW system has two modes, direct and normal. Normal mode has envelope protection that includes overspeed and underspeed, pitch, roll and g-load limits. “That's different from Airbus, where they have multiple different modes and pilots have to train on each one,” says Dewar. “We decided that we have a lot of redundancy, and you need multiple failures to get into direct mode. We really only have to train two modes, which is a big advantage, and that's what the industry gave us back in terms of feedback.”
Bombardier has been testing its first two flight-test aircraft in direct mode and plans to switch to a software load with normal mode this month. At the time of Aviation Week's visit in mid-February, pilots had been testing the normal mode software in the engineering simulator for more than a month. Direct and normal modes both have stick shaker and aural low-speed warnings.
Preparing the flight deck for takeoff, Elliott notes that the CSeries was designed from the start to be paperless, including charts and checklists. Rockwell Collins is developing an electronic checklist that Dewar says will contain “normal” and non-normal” checklists that query sensors to verify the status of items—if the landing gear is down, the system puts a check mark in the box. Dewar says the checklist will be operational for entry into service.
Elliott set the flaps to the Flaps 4 position for takeoff. After switching off the electric parking brake, he increased thrust to takeoff power, noting that there is “nothing startlingly different” about the Pratt & Whitney geared turbofan engines on the CSeries. Power levels are based on the N1 speeds, and shading from parameters in the flight management system (FMS) shows the pilot the commanded takeoff thrust as the engine spools up. Elliott notes that the FMS was totally redesigned by Bombardier pilots and operates as a “phase of flight” system that is “easy and intuitive”
Accelerating through 30 kt., the airspeed tape on the PFD comes “alive” and passing through the rotate speed; the pilot lifts off by pulling back on the sidestick, which provides rate inputs to the pitch and roll axes. The PFD has a flight path vector, showing the aircraft's path with respect to the horizon and, once synthetic vision is installed, the terrain and runways.
With the autopilot turned off, the attributes of the modified C* (C-star) FBW design quickly become clear. While a basic C* FBW blends g force and pitch rate to control the pitch axis, Bombardier modified the control system to be speed-stable, meaning that it attempts to maintain a speed set by the pilot using the trim switches at the top of the sidestick. The commanded speed shows up as a speed “bug,” or pointer, on the speed tape in the PFD.
The energy-based control design mimics the basics of how pilots learn to fly: Set the desired power level and hold the correct pitch of the nose with the elevator to capture a target speed, taking out the pressure on the control yoke with the elevator trim control. When trimmed out, the aircraft will attempt to maintain that speed despite changes in power. If the power is greater than needed, the aircraft will climb, and vice versa, but the speed will attempt to remain constant.
“It's much more intuitive and flies much more like a conventional aircraft,” says Dewar. “Compared to the Airbus FBW, where you trim to an attitude and it holds it, here you trim to an airspeed.”
Elliott says the idea came from pilots. “Go way back to your basic aerodynamics , the simple way pilots learned to fly,” he says. “All the way through, we've tried to make it as pilot-intuitive as possible; in that way we're trying to reduce the training footprint as much as possible. By regulation, we will still have to spend a certain amount of time for a type rating. But it means that instead of teaching them about systems that should be intuitive, we can concentrate more on what they really need to concentrate on: flying the airplane safely.”
Elliott then demonstrated the normal mode envelope protection. If the pilot rolls into a bank of 30 deg. or less, the bank angle remains when the stick is released. For angles greater than 30 deg., the roll angle decreases back to 30 deg. when the stick is released. If the stick is held in the bank, the ultimate limit is an 80-deg. angle. Pitch is limited to 30 deg. nose up and 20 deg. nose down, with the aircraft returning to the previously trimmed airspeed when the stick is released. For nose-up pitch, the sidestick includes a “soft stop” the pilot can muscle through to a hard stop for abrupt maneuvers that exceed the normal g-limit of the aircraft. However, beyond the soft-stop limits, the aircraft must be inspected for damage.
“This is the philosophy between Boeing and Airbus, which we debated heavily,” says Dewar. “The Airbus philosophy is to never exceed limits by the computer taking priority over the pilot. The Boeing philosophy is that the pilot has full authority to absolute structural limits. We combined the two: For normal operations we have soft stops within design limits, with no inspection required. But for an exceptional event—traffic alert or terrain—you can go beyond the normal limits and have structural inspection.”
On landing, Elliott instructed me to trim the speed to 130 kt. with the autothrottle on as we descended toward the runway. At 50 ft., I pulled back on the sidestick to arrest the sink rate. At 30 ft., he closed the throttles and I flared for a nice, but virtual, touchdown, controlling direction with the rudder pedals as Elliott brought in full reverse thrust.