. . . in, arguably, the world's most advanced jetliner
Pilots who strap into 's new 787 most likely will conclude that it is the easiest to fly and most intuitive jetliner ever built by the Seattle-based manufacturer, based upon our findings during a demo flight in mid-November. Five large-format LCD screens have 40% more display area than those in the , making room for better graphics that improve situational awareness. Standard left- and right-side head-up displays, plus left- and right-side electronic flight bags, (EFB), among other features, provide both pilots an equal access to all technology features. Enhancements to the digital fly-by-wire (FBW) flight-control system, adapted from the system used on 777s, make the new aircraft even more docile to handle, resulting in broader safety margins.
While the 777 and 787 share a common pilot type rating because of similar cockpit layouts, systems designs and handling qualities, there are substantive differences between the two aircraft. The 787 is the first commercial jetliner to have a primarily composite airframe. It has a higher aspect ratio wing with a 5% better lift-to-drag ratio than the 777.
The 787's higher bypass-ratio engines do not suffer efficiency losses from constant extraction of bleed air. The aircraft has a nearly all-electric systems architecture, except for high-pressure hydraulics to power some heavy loads and engine bleed air that is used occasionally for nacelle inlet anti-ice protection. Cabin pressurization is higher, so both crews and passengers will experience less fatigue on long flights. And the aircraft's more aerodynamic nose and windscreens means there is less ambient noise in the cockpit.
engineers took on large-scale technology risks in designing this aircraft. Their goals included a 20% reduction in fuel burn, a lighter weight airframe and 30% lower maintenance costs than the 767, the aircraft that the 787, aka the “Dreamliner,” will replace in the model lineup. Increased range, a boost of cruise speed by nearly 30 kt., and an overall more comfortable passenger cabin were also key goals.
Overcoming some of the major risks was part of what led to a three-year delay in the aircraft's initial entry into service. The joints between the center wing carry-through box and main wing structures proved to be too weak, thus requiring modifications. An electrical fire in one of the aft-mounted large motor controllers, caused by metal foreign object debris, grounded flight-test aircraft until those boxes could be redesigned and hardened against moisture and metal-shaving intrusion. Myriad problems with outside suppliers also caused program delays.
After the aircraft went into service in October 2011, other snags emerged. Oneturbofan developed cracks in its fan mid-shaft. A manufacturing flaw in the aft fuselage section caused delamination of the carbon-fiber plies, resulting in extensive rework of several aircraft.
Boeing claims those woes now are history. At present, dispatch reliability exceeds 99%. Having delivered 38 aircraft and satisfied that they had matured sufficiently, Boeing invited Aviation Week to fly the 787 for an evaluation in mid-November.
Composite construction enabled the manufacturer to design a relatively stiff 10:1 aspect ratio wing for better lift-to-drag performance. Cabin pressurization also could be higher without incurring a significant weight penalty. Outside suppliers build large subassemblies that are shipped to Boeing facilities at Everett, Wash., and North Charleston, S.C., where they are joined using mechanical fasteners. Compared with conventional aluminum airframes, assembling the composite structure requires much less hand labor.
The 787 relies heavily on electrical power for functions that were powered by bleed air or hydraulics aboard the 777. Engine start, pressurization, horizontal stab trim, airframe ice protection and wheel brakes, for instance, are electrically powered. Each engine has two 250-kva starter generators in contrast to the single 120-kva integrated-drive generators on each engine of the 777. In addition, the auxiliary power unit (APU) has two 225-kva starter generators, thus there is a total 1.45 megawatts of power available. Each of the six starter generators produces three-phase, 235-volt alternating current (VAC) power. The 787 is also the first civil aircraft to have lithium-ion main batteries.
The starter generators are direct drive, so AC frequency varies with engine speed from about 360-800 hz. Approximately 40 systems, such as the wing anti-ice heaters, main fuel pumps, horizontal stab trim, alternate flaps and cargo bay heaters, are designed to use 235-volt variable-frequency AC power. Much of the 235-VAC power, though, is converted into 115-VAC 400-hz. three-phase, 28-volt DC and ±270-volt DC for use by other electrical systems.
High-amperage ±270-volt large-motor controllers—essentially liquid-cooled transformer rectifiers—supply power to variable-speed motors for hydraulic pumps, cabin air compressors, engine and APU starting, center tank fuel pumps and the fuel tank nitrogen inerting system, among a dozen such loads.
A network of 17 remote power distribution units supply 115Vac and 28Vdc for lighting, wheel brakes, avionics, windshield and air data probe heat, engine igniters, and cabin/galley services. The power supplies also provide secondary and back-up power for the digital fly-by-wire flight-control system.
In the cockpit, the 787 has electronic (“virtual”) rather than physical circuit breakers. These are monitored and controlled by means of point-and-click commands on a circuit breaker schematic displayed on the engine-indicating and crew-alerting system.
All fuel is stored in wet main and center wing tanks that are flooded with nitrogen to inhibit fuel vapor combustion. There are dual-AC fuel-boost pumps in each wing tank and center fuel tank. If no AC power is available, a stand-alone DC boost pump in the left main fuel tank supplies fuel for APU starting. If a fuel imbalance develops, the flight crew can balance the load simply by pressing a “balance” button in the overhead panel.
The aircraft has been upgraded with a 5,000-psi hydraulic system that uses smaller lines and actuators, thereby saving weight. Similar to the 777, the new aircraft has left and right engine-driven pumps. But, the left, right and center system pumps have variable-speed DC motors rather than constant-speed AC motors. The center system has two high-voltage DC pumps rather than two AC and two on-demand, bleed-air-powered pumps.
Hydraulic power is used for virtually the same functions as aboard the 777, but the normal and alternate wheel brakes are 28Vdc-powered.
The 787's digital fly-by-wire flight-control system architecture is similar to the 777 and it uses the same C*U (pronounced “Sea Star U”) pitch control law. C* means that fore/aft yoke movement commands pitch rate on the ground, and g rate or vertical acceleration (Nz) in the air. U means that speed stability is built into the control laws, so the pilot has to manually trim pitch in flight with speed changes.
A number of new FBW enhancements are on the 787. Roll control now is fully fly-by-wire. There is a “P-beta” yaw and roll asymmetry compensation function that uses inertial inputs from the Earth reference systems to counter weathervaning during crosswind takeoffs and landings plus thrust asymmetry during an engine failure.
Maneuver load alleviation progressively extends the outboard spoilers during high-g conditions to reduce wing-bending stress. Gust load alleviation also extends the spoilers and deflects the ailerons to reduce wing-bending in turbulence with the autopilot engaged. Autodrag helps the flight crew descend from above to capture glideslope/glidepath while maintaining airspeed at idle thrust by deflecting the ailerons downward and outboard two spoilers upward if the landing gear are extended and flaps are set to 25 or 30 deg.
Tail-strike protection decreases the risk of ground contact during takeoff and landing by decreasing elevator deflection. The cruise-flaps function automatically adjusts the flap, aileron, flaperon and spoiler positions at Mach 0.54-0.87 above flight level (FL) 250 to optimize wing camber for cruise efficiency.
When boarding the aircraft, I noted that the L1 main entry door is located relatively close to the left angle-of-attack (AOA) vane. Airlines are advised to train ground crews carefully in how to position the passenger boarding bridge to avoid damaging the AOA vane.
I strapped into the left seat of ZA005, the fifth flight-test article, with Capt. Mike Bryan, assistant chief 787 pilot, in the right seat as instructor and Heather Ross, 787 engineering project pilot, riding along in a jumpseat as safety pilot.
We used 115Vac ground power to supply the avionics and systems prior to APU start. Notably, ground electrical power can be used to supply the cabin pressurization pumps and thus air-condition packs. With at least two ground power sources, preferably three, the main engines also can be started on ground electrical power. However, airline operators say that the aircraft is sensitive about the quality of ground power, so voltage, frequency or amperage variability may affect aircraft electrical system performance.
Bryan explained that Boeing FBW aircraft have back-driven and interconnected yokes and rudder pedals, along with back-driven throttles and speed brake handles, that provide visual and tactile cues of what is going on in the cockpit. This is in contrast to some FBW aircraft fitted with side-stick controls that are not interconnected or back-driven and auto-throttle systems that do not move the thrust levers. It is more difficult in such cockpits to keep all flight crewmembers in the situational awareness loop, Boeing engineers assert.
But, Bryan also says that, unlike the 777, the 787 has no dedicated control display units for the flight-management computers (FMC). Multifunction keyboards on the center console are used to enter characters in the scratchpad field of a virtual control-and-display-unit (CDU) graphic on any one of three display screens. The scratchpad contents then are transferred into selected fields using a touch pad cursor control device. Without dedicated FMC CDUs, I would prefer a touchscreen user interface in place of the cursor control device entry method.
Using the virtual CDU, Bryan typed and clicked in our flight plan from Seattle-based King County International Airport/Boeing-King Field to Moses Lake-Grant County (Wash.) International Airport. He also used the interactive electronic checklist to run through pre-start checks. The system automatically checks off items when it senses that they have been completed.
We used the onboard performance tool software, hosted by the fully integrated electronic flight bags, to compute optimum slat/flap settings and V speeds for takeoff. Runway 13R was the active at Boeing-King Field. The temperature was 4C (39.2F) and the altimeter setting was 29.92. Based on a 350,000-lb. (158,757-kg) takeoff weight, the EFB recommended using slats/flaps 5 deg. It computed the V1 takeoff decision speed at 132 KIAS, 136 KIAS for rotation and 148 KIAS for the one-engine-inoperative takeoff safety speed. At the touch of a button, the EFB sends these data to the FMC and avionics system for indications on the primary flight displays.
After I started the APU, we used it to supply electrical power to start both main GEnx-1B70 engines simultaneously. A glance up at the overhead panel confirmed that knobs at 12 o'clock, and annunciator lights out, signified no problems. The electronic engine controls [full authority digital engine controls] handled all start functions.
It took very little thrust to move out of the chocks because the aircraft only was loaded to 70% of maximum ramp. Braking action was smooth and the tiller-controlled nosewheel steering precise. The rudder pedals command up to 8 deg. and the left and right tillers command up to 70 deg. of nosewheel steering.
Aligning the aircraft on Runway 13R, we pushed up the thrust levers midway, waited for the engines to stabilize at 40% N1 fan speed and engaged the auto-throttles. N1 stabilized at 94% as the engines produced their full 70,000-lb./takeoff thrust rating. With a 1:2.5 thrust-to-weight ratio, the lightly loaded aircraft had rather sporty acceleration.
Light back pressure on the yoke produced crisp but smooth pitch response. I followed the flight director cue in the head-up display to hold 10 deg. nose up. The test card called for me to engage the autopilot after retracting the gear and flaps. But, I elected to fly the aircraft by hand, using the HUD as the primary flight reference, for almost all my time in the left seat in order to evaluate the aircraft's handling qualities to the fullest.
Trimming for changes in airspeed takes just one touch of the trim switch to reset the trim reference airspeed. This does not directly move the horizontal stabilizer. Rather, the FBW system initially moves the elevators to change the trim and then follows up with stab trim to minimize trim drag. The control yoke does not change position with trim actuation.
Roll control, fully managed by the primary flight control computers, was silky smooth and nicely responsive, but not overly so. The FBW system provides artificial spiral stability up to 35 deg. of bank. There are no hard bank limits, so the aircraft can be rolled much steeper. But when the yoke is released, the FBW system forces the control wheel in the opposite direction to reduce bank angle to 30 deg.
Bryan also demonstrated how the P-beta function prevents thrust asymmetry or other uncommanded event from upsetting the aircraft in roll or yaw. In a stable 30-deg. bank angle, he retarded one throttle and advanced the other. The thrust asymmetry produced only the slightest change in yaw and virtually no change in roll angle. He repeated the process by reversing each throttle position. The result was the same. No upset, but enough seat-of-the-pants feel to detect the thrust asymmetry.
It is extremely unlikely that flight crews would ever experience a failure of the primary flight control computers that could cause the aircraft to be uncontrollable, but the engineers installed a switch in the overhead panel that allows pilots to disable the computers if they malfunction. Bryan then switched off the primary flight control computers so we could fly the aircraft using direct law. This enables the yoke and rudder pedals directly to command the positioning of the flight-control surfaces. The aircraft is completely controllable, but control response is comparatively crude and there are no flight envelope protections available.
The 787 also has protection against pitot/static system failure, such as an icing blockage. Switching to alternate air data enables the aircraft to compute airspeed and altitude from aircraft weight, configuration, AOA and 3-D GPS position. Using alternate air data, Bryan noted only a 8-9-kt. difference in airspeed and a 40-ft. variance in altitude while cruising at 300 KIAS and 16,000 ft.
We then proceeded to Moses Lake-Grant County for pattern work. We deliberately stayed high prior to descending for the instrument landing system (ILS) approach to Runway 32 so Bryan could demonstrate the aircraft's new autodrag function. The aircraft is so clean that it is difficult to descend to and capture glideslope or glidepath from above, even with gear down, flaps set to 25 or 30 deg. and idle thrust. Under these conditions, the autodrag function deflects the ailerons downward and two outermost spoilers on each wing upward to assist in descending without gaining airspeed. The function is phased out gently below 500 ft. above ground level so that normal flare and landing behavior is not affected.
Our first approach was a normal, all-engine, full 30-deg. flap maneuver that was hand-flown using the HUD and auto-throttles. Aircraft weight was 340,300 lb. Bryan bugged the target airspeed at 142 kt., 5 kt. above Vref. The aircraft was very stable, yet responsive to control inputs. It was easy to stay on localizer and glideslope via the HUD's precision guidance. Over the touchdown zone and 30 ft. above the runway, we flared slightly and touched down gently.
Bryan retracted the flaps to 5 deg., adjusted pitch trim and we advanced thrust for the go-around. On the downwind leg, he pulled back the right throttle to idle to simulate an engine failure. The P-Beta function stabilized the aircraft in yaw and roll. The left auto throttle adjusted the thrust as needed.
Based on a landing weight of 339,600 lb. and using Flaps 20 deg., Bryan set 146 KIAS as the target speed. The left auto throttle maintained that speed within 1-2 kt.
At ILS minimums, we executed a go-around. Bryan instructed me to leave my feet on the floor and allow the P-Beta system to counter the thrust asymmetry. The aircraft lost none of its composure during the maneuver, but there was noticeable side slip to the right caused by the left engine's higher thrust output.
We continued the simulated one-engine-inoperative abnormality for our final landing at Moses Lake. Using Flaps 20 deg. and based on a landing weight of 337,600 lb., Vref was 140 KIAS and the target airspeed was 145 KIAS.
Touchdown was smooth, but I floated a little too long in ground effect. I relaxed prematurely. Make a note. You must fly the nosewheel down to the runway, or you can be embarrassed by an audible thump during the derotation.
The 787 is indeed the nicest handling and most docile handling Boeing jetliner I've yet flown. Enhancements to the company's FBW flight-control system increase safety margins and make the aircraft impressively pleasant to hand fly.
The aircraft can be flown with equal ability from either seat because the left and right sides have the same access to displays, controls and tools, including left and right HUDs, EFBs and steering tillers. Situational awareness and crew resource management are top notch because of the moving and interconnected control yokes and rudder pedals, along with the back-driven throttles and speed brake handle.
Admittedly, the aircraft entered service three years later than planned. But, judging on performance, it was worth the wait.
Fly along with Aviation Week Editor Fred George as he tries out the 787's advanced features: watch a brief video of his flight in the digital edition of AW&ST on leading tablets and smartphones, or view the full-length video on the 787 Pilot Report Special Topic page at AviationWeek.com
|Wing Loading||129.5 lb./sq. ft.|
|Power Loading||3.48 lb./lbf|
|Noise: TO/sideline/app (EPNdB)||87.4/91.5/99.6|
|Seating: crew + normal pax/max pax||10 + 242/381|
|Length||186.1 ft./56.7 meters|
|Height||55.5 ft./16.9 meters|
|Span||197.3 ft./60.1 meters|
|Length||137.1 ft./41.8 meters|
|Height||8.1 ft./2.5 meters|
|Width (maximum)||18.0 ft./5.5 meters|
|Width (floor)||17.8 ft./5.4 meters|
|Engine||2 General Electric GEnx-1Bs*|
|Output/Flat Rating OAT°C||72,300 lb. each|
|Inspection Interval||30,0O0 hr.|
|Max Ramp||503,500 lb./228,386 kg|
|Max Takeoff||502,500 lb./227,933 kg|
|Max Landing||380,000 lb./172,367 kg|
|Zero Fuel||355,000 lb./161,027 kg|
|Operating Weight Empty||259,700 lb./117,799 kg|
|Max Payload||95,300 lb./43,228 kg|
|Useful Load||243,800 lb./110,587 kg|
|Normal Payload||50,820 lb./23,052 kg|
|Max Fuel||223,378 lb./101,324 kg|
|Payload with Max Fuel||20,422 lb./9,263 kg|
|Fuel with Max Payload||148,500 lb./67,359 kg|
|Fuel with Typical Payload||192,980 lb./87,535 kg|
|FL/Vmo||FL 281/360 kt.|
|Cabin Pressurization||9.4 psi|
|Certificated||43,100 ft./13,137 meters|
|All-Engine Service||34,600 ft./10,546 meters|
|Engine-Out Service||14,500 ft./4,420 meters|