C Series - Pilots Report

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Pilot Report: Bombardier’s C Series Sets New Standard

Cockpit ergonomics, fly-by-wire and sidestick advances make C Series docile but responsive http://aviationweek.com/commercial-aviation/pilot-report-bombardier-s-c-series-sets-new-standard

Feb 3, 2017Fred George | Aviation Week & Space TechnologyIN

COMMENTS 7

 

Class Redefined

RELATED MEDIA

Podcast: Flying The C Series. Our Pilots Report

 

Bombardier’s C Series is an iconoclast, defining a new class of passenger jets that defies traditional classification as either regional or transcontinental airliners because of its size, range and operating costs.

The C Series is a clear departure not only from Bombardier’s successful CRJ family of regional jets but also from the 100-115-seat, 1,500-2,400-nm-range BRJ-X that the Montreal-based company abandoned in 2000 when it was confronted with stiff competition from Embraer’s new E-jets as well as the Boeing 717 and AirbusA318. Instead, Bombardier elected to retreat and regroup.

After a four-year time-out, Bombardier decided it was time for a bold step forward. It created the C Series, a clean-sheet aircraft capable of flying 110-150 passengers up to 3,300 nm at Mach 0.78. The aircraft was planned to enter service in 2010. But numerous fits and starts delayed the initial CS100’s entry into service to mid-2016 and the stretched CS300 to December 2016.

The competitive landscape is far different today than in 2010, with Embraer’s more capable E-Jet E2 regional jets due to enter service beginning in 2018. Embraer predicts the E190-E2 will fly 97 passengers 2,800 nm. The 108-127-seat CS100 will fly 3,100 nm, says Bombardier, and passenger capacity may be increased to 135 in the future.

SOME KEY FEATURES OF BOMBARDIER CS300

Aircraft shares 97% of its parts with the CS100

Composites helps reduce CS300’s operating empty weight by at least 2,500 lb. over a conventional aluminum-alloy airframe

Cockpit is designed for extensive electronic checklist

Optional head-up display and electronic flight bags are slated to be certified soon

Landing performance reminiscent of short-field work using robust braking in a straight-wing Cessna Citation

The CS300, meanwhile, competes head-on with transcontinental-range jetliners from Airbus and Boeing which, in response to the C Series, have reengined their respective A320 and 737 families, the A320neo entering service in 2016 with the 737 MAX to follow in 2017. Bombardier’s lead has evaporated; can its new aircraft compete? Marquee orders from Air Canada and Delta Air Lines in 2016 suggest the C Series can.

Sharing 97% of its parts with the CS100, the CS300 is stretched 12.2 ft. to increase passenger capacity to 145, and perhaps to 160 with additional certification work. The CS300 has a range of 3,300 nm at Mach 0.78, opening up city pairs such as Portland, Oregon-Charlotte, North Carolina; Shannon, Ireland-Toronto; and Anchorage, Alaska-Cabo San Lucas, Mexico. 

The C Series has a narrower cabin than the Airbus or Boeing single-aisles, but its two-by-three seating allows for wider seats than most competitors’. The majority of its economy-class seats are 18.5 in. wide, with the middle seat being 19 in. wide to make it more tolerable. The aisle is 20 in. wide. Cabin windows are 11 X 16 in., the largest in the single-aisle class. Overhead bins are generously sized, able to accommodate 25-in. oversized roller bags on the right and standard 22-in. bags on the left. Interior sound levels are among the lowest in class, based on my observations.

The C Series’ operating empty weight is reduced by at least 2,500 lb. over a conventional aluminum-alloy airframe through use of advanced materials—third-generation aluminum-lithium for the fuselage and resin-transfer-infused carbon fiber for the wing. This makes the CS300 significantly lighter than the smallest members of the A320neo and 737 MAX families.

The C Series is powered by four variants of the Pratt & Whitney PW1500G geared turbofan, with 18,900-23,300-lb. takeoff thrust, flat-rated to ISA+15C (86F). The 73-in. fan turns slower than 3,500 rpm because of a 3:1 reduction gearbox between the low-pressure spool and the fan, with its hollow aluminum blades. The engine has a 12:1 bypass ratio and dual-channel full-authority digital control.

Bombardier’s first fly-by-wire aircraft, the C Series has a three-axis digital flight control system with three triple-channel primary flight control computers that control elevators, rudder, ailerons, spoilers and horizontal stabilizer. Only one computer is in control at a time; the other two monitor its performance. Commands are sent to electro-hydraulic flight control actuators and the horizontal trim motor via 10 remote electronics units.

Control inputs are provided by left and right sidesticks with switches for pitch trim, sidestick priority and aileron and rudder trim, as well as rudder pedals, spoiler lever and takeoff/go-around buttons, plus data from three inertial reference units and four air data probes.

 

The CS300’s 3,300-nm range opens up city pairs such as Shannon, Ireland, to Toronto and Anchorage, Alaska, to Cabo San Lucas, Mexico. Credit: Bombardier

 

The fly-by-wire uses a modified C*U control law, providing G load and/or pitch rate [C*] in response to fore/aft sidestick inputs depending on phase of flight, along with speed stability that changes nose pitch to maintain the selected trim speed. Within the normal flight envelope, pitch-trim inputs reset the trim speed. The selected trim speed is displayed as a cyan bug on the airspeed tape.

Normal law provides three-axis flight control with excess attitude, overspeed, angle-of-attack and load factor envelope protections. Functions include yaw damping, tailstrike protection and partial thrust-asymmetry compensation following an engine failure.

If normal control law is not available due to multiple system failures, such as all three computers failing, an alternate flight control unit provides direct control of the elevators, rudder, ailerons and horizontal stabilizer. The hydraulically actuated leading-edge slats and trailing-edge Fowler flaps are controlled separately by dual slat/flap computers. Ailerons droop 5-10 deg. with flap extension to increase lift.

For our evaluation flight, we boarded aircraft MSN 55002, the eighth C Series flight-test vehicle (FTV) and second CS300, at Bombardier’s Wichita facility, and I strapped into the left seat. Senior flight-test pilot Andy Litavniks belted into the right seat, chief test pilot Dave Lewandowski occupied the jump seat as safety pilot and flight-test engineer Tony Dunne sat at the mid-cabin flight-test console.

MSN 55002 has a full production interior, including galley and vacuum lavatories, but it weighs 84,200 lb., about 2,200 lb. more than typical customer aircraft, because of its flight-test equipment and wiring. FTV 8 was being used for extended twin-engine operational performance standards certification during the week Aviation Week flew it.

 

 

With 400 lb. of payload and 15,000 lb. of fuel, ramp weight was 99,600 lb. This aircraft is fitted with PW1521G turbofans, rated at up to 21,000-lb. thrust for takeoff. Customers also may order PW1524Gs or PW1525Gs with 23,300-lb thrust: The PW1525G has 5% more high-altitude, high-speed cruise thrust.

Flaps 2 (slats 21 deg./flaps 10 deg.), flaps 3 (slats 21 deg./flaps 15 deg.) or flaps 4 (slats 24 deg./flaps 25 deg.) may be used for takeoff. We chose flaps 4 to shorten takeoff field length, but at the expense of lower one-engine-inoperative climb performance. Using full takeoff thrust and based upon Wichita’s 1,333-ft. field elevation, -5C outside air temperature and 30.31-mb. (sea-level) altimeter setting, Dunne computed the numbers for an estimated takeoff weight of 98,600 lb. V₁ takeoff decision speed was 100 kt. indicated airspeed (KIAS), rotation 103 KIAS and V₂ one-engine-inoperative takeoff speed 114 KIAS. Takeoff field length was 3,402 ft. Production C Series come with airplane flight manual software that automatically computes takeoff and landing performance numbers.

The C Series cockpit layout sets high standards for ergonomics, situational awareness and low workload. The tactile feel and positions of knobs and most switches, particularly those on the overhead panel, would work well during a blindfold cockpit check. I especially appreciate the left and right control tuning panels in the glareshield, providing immediate access to communication/navigation/surveillance radio control and display functions, plus altimeter baro set, and one-touch access to flight management system (FMS), map, data, checklist and radio functions on the inboard multifunction displays.

The cockpit is designed for electronic checklist use, to prevent pilots from skipping over or forgetting to return to deferred items. The software interacts with many aircraft systems, so it automatically completes the associated checklist items if switches, knobs and buttons are in their correct positions.

Checklists are comparatively short. After setting the parking brake, switching batteries to auto and pulling up the electronic checklist on the pilot’s inboard display, we only had to check hydraulic panel knob positions, verify the engine run switches were off, plus a few other items, before we were ready to start the auxiliary power unit (APU).

Once running, the APU automatically powers all AC busses and furnishes bleed air for the air-conditioning packs. Everything comes to life in the cockpit. Running the pre-start electronic checklist is easy. The FMS is programmed by phase of flight or function, selected by clicking on tabs in the flight management window on the inboard or lower displays. An alphanumeric keypad on the cursor control panel provides data entry.

Starting the engines simply requires turning on the run switches one at a time. The aircraft automatically reconfigures bleed air, air-conditioning, electrical and fuel systems for the start and then again when it is complete. After both engines were running, we checked that knobs were in the 12 o’clock position, verified annunciator switch lights were dark and eyed the engine-indication and crew-alerting system for alerts and warnings. We checked flight control movement and set auto brakes to rejected takeoff in case of an abort.

At our comparatively light weight, little extra thrust was needed to get the aircraft rolling. The rudder pedals provide up to 9 deg. of nosewheel steering. The tiller provides up to 80 deg. for tight maneuvering, handy on a ramp that was designed for Learjets with 50-ft. wingspans. Steering and braking action are smooth and precise, making for a comfortable ride for passengers.

Cleared for takeoff on Runway 19R, I advanced the power levers to check thrust output was even at 50% N₁ fan speed, then moved them forward to 60%, at which point the autothrottles engaged. Dunne recorded initial takeoff N₁ speed at 84.7%, increasing to 86.8% at 140 KIAS.

 

The PW1500G engines’ 73-in. fans have 3:1 gear boxes, thereby improving fan efficiency and reducing noise well below Stage 4 levels. Credit: Bombardier

 

At 103 KIAS and 16 sec. into the takeoff roll, I rotated to 20 deg. nose up and we were off the pavement in 2,700 ft. Sidestick forces were soft, but well damped, more akin to those in a Dassault Falcon 8X business jet than an A320. It is advisable to use a light touch on the sidestick to avoid jarring passengers and cabin crews.

We retracted slats and flaps in stages, on schedule, and settled into a 250-KIAS climb. Light forward pressure followed by a touch of pitch trim neutralized stick force. The trim-speed bug on the primary flight display’s (PFD) airspeed tape helped me visualize the aircraft’s speed-stable trim point.

Outward visibility from the cockpit is excellent with its large windows and steeply sloping nose. We settled into a 280 KIAS/Mach 0.76 climb to flight level (FL) 380 for a cruise check. Once there, the aircraft stabilized at Mach 0.78 in ISA-2C conditions. With the cockpit door open, I noted exceptionally low sound levels in the passenger cabin.

At a weight of 96,700 lb., cruise speed was 445 kt. true airspeed (KTAS) and fuel burn was 3,460 lb./hr. That yielded a specific range of 0.129 nm/lb., in line with Bombardier’s claims for fuel efficiency. This is just a snapshot of cruise performance, rather than an average measurement in calm air well away from terrain. But it is considerably more fuel-efficient than most competitors.

Returning toward Wichita, I extended the spoilers to maximum to hasten the descent out of Class A airspace. There was a slight nose-up pitching moment at maximum extension but little buffeting as the aircraft descended in excess of 6,000 ft./min.

In visual-flight-rules conditions, down at 16,000 ft., I slowed the aircraft, extended the landing gear and flaps 4 and robustly rolled the aircraft up to 45-deg. bank. Roll response was crisp, but well damped, a tribute to the fly-by-wire control system.

 

Andy Litavniks (right), Bombardier’s senior flight-test pilot, and Aviation Week’s chief evaluation pilot, Fred George, prepare to fly the CS300. Credit: Bombardier

 

We extended gear and flaps, then began a 3-deg. descent at a V_REF speed of 121 KIAS to simulate landing approach. At 15,000 ft., I executed a go-around by selecting maximum thrust, retracting flaps to 2 and raising the landing gear with a positive rate of climb. There was virtually no thrust/pitch coupling or pitch change with configuration change because of the pitch moment compensation provided by the fly-by-wire system.

Our second mock approach at altitude simulated an engine failure on go-around, with Litavniks retarding the right engine to idle. Using full thrust on the left engine, I pushed on the left pedal to put in 9-12 deg. of rudder and pitched up to hold the target VAC approach climb airspeed of 127 KIAS, following the beta (yaw) and pitch targets provided by the PFD. I retracted flaps to 2 to reduce drag, retracted the gear with a positive rate of climb and accelerated to the 137 KIAS VGA go-around target speed. There was little roll moment. Handling was docile as we continued to accelerate to the 177 KIAS final takeoff speed, the point at which I retracted slats and flaps.

We then flew a series of approaches to stalls in various configurations, straight ahead, in banked turns and with increasing load factor. These exercises not only highlighted the flight-envelope protections provided by the fly-by-wire system, they also enabled us to sample the improved situational awareness provided by the semi-active sidestick inceptors that have integrated stall-warning stickshakers and graduated force feel with soft and hard stops.

For instance, during a straight-ahead approach to stall with gear down and flaps 4 selected, I decelerated at 1 kt./sec. from a 121 KIAS landing approach speed. I gently pulled back on the sidestick to maintain altitude. At 101 KIAS, the sidestick reached its soft-stop limit at 18 lb. of pull and its stall-warning shaker was triggered. Simultaneously, the digital airspeed readout turned amber, and we heard “Speed” from the aural alert system.

Instead of recovering, I pulled back farther, overpowering an 11-lb. step increase in force to move the sidestick beyond its soft stop. Past that point, I had to pull back with 29 lb. or more of force to continue the deceleration. We heard “Speed, Speed, Speed,” and the digital airspeed readout turned red. At 94 KIAS and 15.4 deg. angle of attack, I reached the sidestick’s hard stop, requiring 38 lb. of back pressure. The fly-by-wire system prevented the aircraft from rolling or yawing, easing down the nose just shy of the maximum aerodynamic angle of attack as I held full aft pressure on the sidestick.

We recovered from the stall exercises and headed back to Wichita for pattern work. Our first approach was to the instrument landing system on Runway 19R. For a landing weight of 94,000 lb., and based on using flaps 4, Dunne computed VAC at 125 KIAS, V_REFat 119 KIAS and VGA at 135 KIAS.

 

The window and aisle seats are 18.5 in. wide; the middle seat is slightly wider at 19 in. The aisle itself is 20 in. wide. Credit: Bombardier

 

Intercepting the localizer and then the glideslope, it was apparent the aircraft has comparatively little drag, even with gear down and flaps 3 or 4. Hand-flying the aircraft, I had to use idle power to slow it to VAC. I disconnected the autothrottles at 1,000 ft. above mean sea level in accordance with a flight-test limitation associated with ongoing development work.

We slowed to V_REF over the threshold and started the flare at 30 ft. above ground level (AGL), perhaps carrying a little excess speed. After a little float, the aircraft touched down 1,500 ft. down the 10,300-ft. runway. Using low autobraking and mild thrust reverse, we exited the runway after a 4,500-ft. roll-out.

Litavniks selected flaps 2, and we taxied back for takeoff on Runway 19R. Dunne computed speeds as 105 for V₁, 111 for VR, 122 for V₂ and 172 for V_FTO. Takeoff field length was 3,453 ft. We elected to make a rolling takeoff.

Shortly after liftoff, Litavniks pulled back the right throttle, simulating engine failure. I pitched to maintain V₂ and used moderate left rudder-pedal pressure to keep the beta target centered on the PFD for best climb performance. I retracted the landing gear and achieved a 1,200 ft./min. rate of climb.

Litavniks kept the right throttle at idle as we  leveled off at 3,000 ft., accelerated to 190 KIAS and set flaps 1. Using the same landing V speeds, we returned for a landing approach and simulated a one-engine-inoperative go-around with flaps 4 at 200 ft. AGL. Again, I was impressed with the aircraft’s handling ease, responsiveness and performance reserves.

Our final landing was at 93,300 lb., with both engines available and using full flaps 5. Dunne computed 112 KIAS for VAC and V_REF, 112 KIAS for VGA. Upon touchdown, deceleration was strong with autobrakes set to medium. Landing performance reminded me of short-field work using robust braking in a straight-wing Cessna Citation. We taxied back to Bombardier’s ramp, logging 1 hr. 51 min. flight time and a total fuel burn of 6,720 lb.

I have yet to fly a jetliner with more docile yet responsive handling qualities. Bombardier uses fly-by-wire to tame untoward aerodynamic, configuration and thrust behaviors rather than isolating pilots from the aircraft. The semi-active sidesticks are a leap forward in situational awareness. The speed-stable control law also helps keep flight crews in the loop, providing a natural feel.

Cockpit ergonomics are top-notch in this class, with colors, symbols and graphics used only when needed to enhance situational awareness in the otherwise quiet, dark cockpit. I would like to fly the aircraft again once the optional head-up display is certified, as well as the optional electronic flight bags.

Direct operating costs should be impressively low, with the PW1500G engines saving 18-20% in fuel burn over current-generation engines on aircraft in this class, scheduled A and C checks coming at 850- and 8,500-hr. intervals, and one of the most comprehensive trend- and health-monitoring systems yet installed in this class of aircraft.

The C Series is a new icon in its class. Bombardier has raised the narrowbody bar significantly, but also the list prices compared with its traditional regional jets. The company had to discount steeply to beat Airbus and Boeing to the Air Canada and Delta orders. But now that the CS100 is in service with Swiss International Airlines and the CS300 with AirBaltic, the company is confident the aircraft’s demonstrated performance and economics will carry the day. 

Link to the podcast: http://aviationweek.com/airline-fleets-network/podcast-flying-c-series-our-pilots-report?NL=AW-05&Issue=AW-05_20170203_AW-05_956&sfvc4enews=42&cl=article_3&utm_rid=CPEN1000003028964&utm_campaign=8513&utm_medium=email&elq2=5c54371503a64fd6b373f68db274c01d