Bombardier CRJ1000

There is still life left in Bombardier's CRJ family of aircraft, a test flight of the CRJ1000 NextGen reveals. The future may belong to larger aircraft, such as the airframer's CSeries, but the NextGen family of CRJs delivers a comfortable passenger experience - plus fuel savings of up to 12% on a 1,000nm (1,850km) stage length, compared with competitive aircraft.

Bombardier senior engineering test pilot Andy Litavniks was the host for my flights - one in the CRJ1000 and one in the CRJ700 - conducted from Bombardier's Mirabel CRJ production site north of Montreal. Flying the aircraft back to back allowed me to note how the CRJ1000's fly-by-wire rudder compares with the CRJ700's conventional one.

 

Bombardier CRJ1000, Bombardier
 © Bombardier

 

From a pilot's perspective, the NextGen line offers several advantages. While the flightdeck is still a Rockwell Collins Pro Line 4, it incorporates several Pro Line 21 units.

The altitude heading reference system has been upgraded to laser ring gyros from the previous flux valve units. Optional NextGen cockpit items include a Class 2 electronic flight bag, sourced from CMC Electronics, and a Collins head-up guidance system. With proper training and authorisation, the head-up guidance system can allow for reduced visibility take-offs as well as a Category IIIa landing capability.

Unfortunately, neither the EFB nor the head-up system were installed on the test aircraft, which was a production example in Brit Air colours.

With the outside temperature hovering around -15°C (5°F), the pre-flight walk-around inspection was conducted in the warmth of a hangar. The inspection itself was straightforward, and the longer fuselage and larger wing were obvious.

I used the seat alignment balls on the centre pillar to gain a comfortable seating position. With a few minor exceptions, the flightdeck is identical to that of the CRJ900 I had flown earlier.

The six 6 x 7in (15 x 18cm) cathode ray tube displays - leading edge when the Pro Line 4 avionics suite was first deployed - seem merely adequate in today's marketplace. Aircraft systems are primarily controlled by switches and push-button lights on the well-arranged overhead panel.

The flight guidance control panel on the glareshield provided ready access to autopilot and flight-director modes, and the forward instrument panel was arranged in the conventional manner, each pilot having a dedicated primary flight display and multifunction display.

Two flight management system control units are at the head of the centre pedestal. Unlike the CRJ700/900, which has a manual alternate gear-release lever aft of the pedestal, the CRJ1000's alternate gear system is electrically actuated and controlled by a switch next to the gear lever.

After completion of pre-start flows, both engines were started using bleed air from the tail-mounted Honeywell auxiliary power unit. The automatic starts are triggered by the full-authority digital engine control, the only pilot action being to move the respective throttle from "shut off" to "idle" at 20% N2.

Starter cut-out was at 50% N2, and the peak inter-state turbine temperature of 475°C for both engines was well below the limit of 815°C. Post-start flows were easily accomplished and the flaps were set to position 8 for our take-off. Once the aircraft was rolling, idle thrust was sufficient to move at a comfortable taxi speed. Rudder-pedal-actuated steering gave +/-7° of displacement and was used on the straight portions of the taxi, while the tiller, with +/-70° of displacement, was used for large turns.

During the taxi to Runway 06, I found the steer-by-wire nose wheel steering allowed me to precisely track taxiway centrelines. Mirabel is an uncontrolled field and, after visually clearing final, we lined up on Runway 06. I pushed the throttles to the TOGA detent, N1s settling at 85.9%N1.

On that cold day the aircraft raced down the runway, Litavniks calling "rotate" at an indicated airspeed of 133kt (245km/h). Yoke forces were light as I pulled the aircraft into a 12° nose-high take-off attitude. Had I been overly aggressive during the rotation, an enhanced pitch director mode of the flight director would have commanded a lower rotation rate/pitch attitude in an effort to prevent a tail strike.

Bombardier lists a maximum take-off weight of 40,825kg (90,000lb) for the base line CRJ1000. With 7,785kg of fuel (8,820kg maximum) our take-off weight of 31,300kg was not representative of an actual airline operation. The aircraft cleared the runway after a 1,000m (3,280ft) ground run, about one half of the certificated take-off distance, which includes clearing a 35ft obstacle at maximum take-off weight.

After cleaning up the aircraft, and when passing 1,000ft above the ground, I retarded the throttles to the "climb" detent.

A turn was made to the north, air traffic control clearing Canadair 112 into one of Bombardier's local test areas.

I hand-flew the aircraft until we passed 10,000ft, where a climb speed of 290kt was captured and held by the autopilot. With the throttles in "climb" detent, the full-authority digital engine controls kept the optimum N1 setting. When the aircraft passed 32,000ft, Mach 0.77 was captured and held until we reached our cruise altitude of FL350. Time from brake release to level-off was only about 18min.

RAPID CRUISE

Once level, I established M0.78 cruise point, Bombardier's recommended normal cruise speed. I found the airspeed tape's trend arrow allowed me to expeditiously set and hold the desired speed. A total fuel flow of 1,480kg/h was needed to hold M0.78/262kt with a resultant true airspeed of 454kt.

Next, the power was increased and an M0.80 cruise speed was established. Total fuel flow increased to 1,740kg/h with a resultant true airspeed of 473kt.

To a working airline pilot, the prospect of being stuck behind slower traffic is never appealing. Bombardier's CRJs can definitely keep up with traffic - and even outpace aircraft such as the Boeing 737 Classic.

The ambient noise level was reasonably low, on a par with the flightdeck of a 737. For the flight we used David Clark headsets, which further reduced background noise. At altitude I found the flightdeck a pleasant environment to work in. Given the CRJ1000's 1,345nm range, with 100 passengers and IFR reserves, legs with three-plus hours of block time will not be out of the question.

While still at altitude, Litavniks put the flight-control page schematic up on one of the centre multifunction displays.

The rudder schematic showed actual rudder displacement against a lateral scale. Nothing unusual in that, but what was interesting was the two sets of lateral limits displayed. Large hash marks indicated the ultimate displacement limit, while smaller moving ones inside them showed the displacement allowed given the current flight conditions and aircraft configuration. At FL350 and cruise conditions, only about a quarter of maximum rudder displacement was available.

 

Bombardier CRJ1000, Bombardier
 © Bombardier

 

The CRJ1000 is the only CRJ to have a fly-by-wire rudder. While almost all transport aircraft have some sort of rudder travel limiter, what distinguishes the CRJ1000 is how the FBW scheme is implemented. In the CRJ1000, the pilot always has full rudder pedal travel, only the resultant rudder displacement is reduced.

Reducing rudder pedal travel is another method of limiting rudder displacement. Reduced rudder pedal travel has, however, been cited as a contributing factor in several accidents. The crash of an American Airlines Airbus A300 after take-off from New York Kennedy in 2001 is one salient example.

Bombardier's decision to develop a fly-by-wire rudder for the CRJ1000, instead of using the proven existing design, may have been driven more by a corporate strategy to gain fly-by-wire experience for the forthcoming CSeries than by any pressing technological issues unique to the CRJ1000.

During the descent to medium altitude, I accelerated the CRJ1000 to its maximum of M0.80 at 28,000ft. At MMO, small, sharp control inputs in all three axes elicited a well-damped response.

To slow the aircraft, I retarded the throttles and extended the speedbrakes to their full open position. There was a noticeable burble but no untold pitching motion as the aircraft slowed.

I stowed the speedbrakes and continued the descent to 18,000ft, where I would be able to evaluate the CRJ1000's handling characteristics. At an indicated 300kt, I accomplished a series of 45° angle-of-bank steep turns.

I did these with my feet on the floor, allowing the digital yaw damper - part of the rudder control scheme - to co-ordinate the turns. Roll in and out of the turns was crisp, with good harmony between the pitch and roll axes.

Slowing to 250kt, I again did 45° steep turns. At the higher speed, aircraft response was crisp and the turns well co-ordinated.

The flight-control schematic was put up on a multifunction display where, in a clean configuration and 220kt, a maximum available rudder deflection of 1/4th was indicated.

Next, I did a wings-level sideslip and found breakout forces for the rudder to be about 7kg. Full travel required about 20kg of force, with rudder deflection roughly proportional to pedal forces. Allowable rudder deflection increases as speed decreases and the flaps are extended. Speeds below 150kt and flaps to position 30/45 allow full rudder deflection of 33°. Loss of an engine roughly doubles the available rudder deflection at any given speed and flap setting.

Two stalls were accomplished next. The first was in a clean configuration and with a fuel load of 6,470kg. Slowing at 1kt/s in level flight, trim in the pitch axis was halted passing 166kt. Ignoring the slow speed warning on the primary flight display's airspeed tape, the stickshaker actuated at 142kt.

The wing remained steady and level as the airspeed continued slowing. At 131kt, the stick pusher fired, prompting me to recover the aircraft by lowering the nose to break the stall and advancing the throttles.

Adding power caused a slight nose-down pitching motion, further aiding the recovery. The last stall was in the landing configuration, flaps set to "45" and gear extended. The shaker activated, slowing through 128kt with the pusher firing at 106kt.

As with the clean stall, control in all three axes was good at these very slow speeds. The wings remained level and displayed no tendency to oscillate or drop.

After recovering to normal flight conditions, the gear was retracted and flaps retracted to position "8". At 150kt, a half-amplitude rudder doublet was used to excite the CRJ's Dutch roll mode.

With the yaw damper disengaged, aircraft response was lightly damped with a roll to yaw ratio of about one to one. Engaging the yaw damper served to quickly damp out the motion. Aircraft motion from another rudder doublet, with the yaw damper engaged, was quickly damped out without pilot intervention.

Flight International 29/03/11

Our exclusive, collectible cutaway poster of Bombardier’s CRJ1000 regional jet is included with the next issue of Flight International (29 March-4 April).

The CRJ1000 drawing is the work of our consulting technical artist Tim Hall.