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787 special: Systems advance

More than with any previous airliner, systems improvements form a significant part of Boeing’s overall efficiency targets for the 787

As with the structures, propulsion and aerodynamics, the systems architecture of the 787 represents both a solid step into the future as well as the final product of a distinctly unconventional approach. More than in any previous Boeing commercial design, the systems go beyond pure functionality and represent a means to an end. Collectively they play a pivotal role in improving the overall efficiency of the 787 by 3%, and an important part in meeting the goals of the original 7E7 – or 10% lower operating costs and 20% reduced fuel consumption on a per-passenger basis.

“We tried to approach it without regard to functions, and asked ourselves how we could do it more efficiently,” says 787 systems director Mike Sinnett. “If there was a job to be done on the aircraft pneumatically we asked: ‘Can we do that differently?’,” he adds. “All this was solely based on whether it would mean more economic energy extraction at cruise, where you spend most time. That’s how to dictate the architecture of the aircraft, because that’s how you become more efficient.”

Given this fundamental target, the 7E7 systems design team had carte blanche effectively to throw away the rulebook. “Typically we’d approach the aircraft from an ATA [Air Transport Association] chapter perspective. But from a first principles perspective, we were able to set aside all our more typical prejudices,” he adds.

“It’s really cool to see it all coming together: we have teams around the world working on this, and it is more of an extended network,” Sinnett says. Since then Boeing’s traditional role in the aircraft’s development has morphed into that of a systems integrator, and the company has had to adapt as a result. “It really is different, and our team has to behave differently. We are not directly interchangeable like we were on the 777. We can influence, guide and set direction, but we do not directly control,” he adds, saying that “it’s a mixture of having to let go a little bit, but it’s also a relief to have someone else take responsibility for their part, and let you concentrate on the more important role of putting all the parts of it together”.

Unlike previous programmes where the list of suppliers numbered into the hundreds, the 787 is being put together with a team of just over 30 major (Tier 1) companies. Under the new system, the partners perform far more of their own development, design and manufacturing while working the process in association with Boeing’s life cycle product team (LCPT) organisation. Beneath each Tier 1 name is a sub-set of suppliers for the particular part or system being provided by that team. This fundamentally different approach makes Boeing more of an integrator, and allows it to focus on its prime role of final assembly while allowing its partners to focus on their expertise in developing sub-assemblies and systems. The federation of 787 LCPTs have also formed a partner council that holds regular monthly or bimonthly meetings to share progress and expertise that may help overcome problems.

Flightdeck avionics

“For functionality, the over-arching goal was to improve situational awareness, and the result is seen with the flightdeck design today. It takes the form of the largest flight displays ever done, dual head-up-displays [HUDs] and dual electronic flight bag displays – all of which will be basic,” says Sinnett. “We just provide more display real estate for situational awareness and, behind that, provide capability for even more of that situational awareness all of the time.”

 
Rockwell Collins makes much of the 787 flightdeck, including LCD displays and pilot controls

Systems such as weather radar, enhanced ground proximity warning and traffic collision avoidance (TCAS), for example, are “dual basic” to all aircraft. “So the airline never has to make a choice, and there’s always a hot spare,” Sinnett adds. “Some pilots like them, some don’t.” However, Sinnett acknowledges that “in some discussions with airlines it was an issue. But everyone will have two HUDs, and it is just the way it will be. Some chief executives think they’re just pilot’s toys, but we believe in our hearts that the more awareness the pilot has, the better it is.”

The luxury of in-built redundancy on this level came at a price. “We had tough cost targets and we thought long and hard about offering less than we did. In the end we decided that as this approach basically doubles the size of the market, the unit cost drops and it becomes a more efficient way of managing options.”

Pilots visiting Boeing will get a chance to see for themselves how the new flightdeck design should improve situational awareness with the Mark I eyeball alone, if nothing else. Larger windows have replaced the traditional narrow Boeing front and side direct-vision flightdeck windows, and the “out the window” view through the enlarged transparencies has been evaluated in an engineering simulator and emergency egress has been demonstrated using a mock-up. Total flightdeck window space for the 787 is 3.1m2 (33.5ft2) compared with 2.5m2 for the 767/777.

Meanwhile, tests have begun on the initial “red label” Rockwell Collins 23 x 30.5cm (9 x 12in) primary flight displays, five of which will occupy the flightdeck. “We have lots of different pieces of hardware in different stages of test and development,” says Sinnett. One complete shipset of displays has been delivered to Boeing’s integration facility in Seattle, says Greg Irmen, senior director Boeing programmes for Rockwell Collins. The batch also includes seven core networks, a complete pilot controls system, the latter set being designed and built at the company’s Irvine, California site.

Rockwell Collins has also delivered more than 100 Ethernet switches to Smiths Aerospace, and has shipped the first production components (remote light sensors) to Japan. “The majority of our production deliveries, however, start shipping in November through February, and will go to Spirit AeroSystems in Wichita,” says Irmen, who adds that the company will also be sending “a few components to Italy [Alenia] that are part of the communications/surveillance package”. Rockwell Collins also supplied keypads and cockpit cursor control devices and says they are “a bit more advanced on the 787, in that they have been designed with ARINC 429 ASICs embedded to reduce the complexity of the interface with the aircraft”.

Goodrich, meanwhile, provides the flightdeck entry video surveillance system, which uses a set of concealed high-resolution infrared cameras and a security camera interface unit to send digital video images to the flightdeck’s electronic flight bags. The cameras “see in total darkness,” adds the company.

Common core

Control and the eventual updating of the aircraft’s systems is also being made easier by the adoption of an open-architecture and a common core system (CCS). Developed by Smiths Aerospace, the CCS concentrates the processing functions of many different systems in one spot, saving weight, cost and power. The CCS concept allows the avionics system to be upgraded almost as easily as a modern PC.

“Boeing has chosen to design the 787 a little bit differently by using the CCS,” says Smith’s 787 CCS programme director Mike Madden. “It is a scaleable and modular system, which means you can add elements of the system without having to redesign the entire thing, and its modularity means these elements are all common.”

This evolutionary leap follows the gradual migration from avionics designs made up of a collection of federated, specific functions to open and integrated modular architectures (IMAs), in which more and more functions are tied together. With the 787, however, Boeing has gone a step further and provided an open-standards computing “platform” where more than 80 functions are combined into one computer system. The CCS builds on the foundations laid by the C-130 aircraft modernisation programme (AMP) upgrade and the 777’s aircraft information management system (AIMS) concept. The 777 has around 80 separate computer systems with about 100 different devices, versus 30 computer systems on the 787.

Data collection

The CCS consists of three main elements, says Madden. These include a common computing resource (CCR) – a cabinet that houses general processing and application-specific modules; a Rockwell Collins-developed common data network, which employs the deterministic Ethernet 664/AFDX (Avionics Full Duplex) standard; and a series of remote data concentrators (RDCs). The network supports both copper and fibre-optic interfaces with connection speeds of 10Mbit/s and 100Mbit/s, or up to 1,000 times faster than the ARINC 429 used in current-generation avionics databus.

Each shipset consists of two CCR cabinets, eight general processing modules, network switches and fibre-optic translator modules (two in each cabinet). Application-specific modules, provided by third parties, can also be installed in the cabinets. “There are open slots in the cabinet that Boeing is allocating to other suppliers,” says Madden. “For example, there are two display processors provided by Rockwell Collins, but they are done under contract to Boeing rather than as part of the CCS on which we are partnered.” The CDN consists of network switches located inside the CCR cabinets and externally mounted throughout the aircraft. The network itself is made up of a fibre-optic Ethernet network that connects all the systems.

 
© Royal King  
Boeing is using a leased 777-200ER for risk reduction tests for the 787 flight control laws

The RDCs, supplied by Smiths’ site in Cheltenham, UK, replace traditional, dedicated signal wiring and concentrate analogue and digital signals from the remote sensors and effectors, feeding them into the network. Each 787 will have 21 of these remote sensors to take measurements and provide a signal input, and effectors send signals to make units such as actuators move. “They are all over the aircraft, literally, because their function is to collect data from everywhere,” adds Madden.

COTS benefits

The 787 will use commercial off-the-shelf (COTS) operating systems from Green Hills Software and Wind River Systems in the core avionics systems. “Wind River is for the CCS in particular, while Green Hills is more for the flight control system,” says Sinnett, who adds the benefits of adopting the COTS approach will be felt throughout the long lifetime of the 787. “Rather than having everyone develop their own interface and operating system, they can plug directly in using these,” he adds. “When something has to be changed and updated, you can change the operating system without having to recertificate the codes.”

Flying right

The 777 uses a flight control law called C*u to fly the aircraft in the pitch (nose up/down) axis. In C*u law, the aircraft’s speed is governed by speed stability rather than pitch – or pointing – stability, which means that if the aircraft’s trimmed speed changes, the pitch will change to return it to the set speed. In roll (wing down/up) and in yaw (nose left/right), control is via a direct electronic signal to the control surfaces. C*u, (pronounced cee star u), also incorporates feedback to the flight control computer to assist the pilot in flying.

Boeing 787 chief test pilot Mike Carriker says “in the 787, we will use C*u for the pitch axis, and in roll yaw, we will use a control law named P-Beta. P is the aerodynamic term for roll rate. Side slip angle, ß (normally spelled out Beta) is the angle between the direction the wind is coming from and the direction the nose is pointed. Generally, P is controlled by the rotating of the control wheel, and ß is created by stepping on a rudder pedal. When the pilot ‘rolls’ the aircraft, a command is sent to the flight control computers for a roll rate, and the computers figure out how much control surface is used to meet the command. When the pedal is pressed, it is a command to establish an angle of sideslip, ß. The hard part is that these two terms have an effect on each other. Get some ß, and you get some roll. Create some roll, create some ß. Sometimes you really want ß, like a crosswind landing, but most of the time you don’t want any. Getting this part correct is the hard part.” Flight test evaluations of the P-Beta laws have been undertaken in a leased 777-200ER. 

Smiths selected Wind River Systems’ VxWorks 653 real-time operating system (RTOS) for the CCS. “We needed a partitioned operating environment that allowed us to share processing resources amongst a number of applications. That maximises the utility of the processors and means you can certificate applications independently of both the platform and one another,” says Madden.

Smiths worked with Wind River’s RTOS on the C-130 AMP and the KC-767 tanker, and is using the relationship to help develop a software common operating environment (SCOE) “that we’d like to use across all these programmes”. The KC-767 application of SCOE is expected to receive certification imminently, and forms a key milestone for the application of the same operating system on the 787.

Smiths plans to supply cabinets to Spirit in Wichita for installation in fuselage Section 41 before delivery. The cabinets will be installed empty and populated in situ. “At this point we’re putting the first together in Grand Rapids, Michigan, but eventually we will be doing it in Wichita,” says Madden, who adds that a final location has yet to be determined. “We have to deliver the first set of hardware before the end of the year to support the ‘de-bugging’ of the first Section 41,” he says.

Honeywell chose the Green Hills RTOS for the fly-by-wire (FBW) flight control electronics. Green Hills’ Integrity-178B will run in the flight control system (FCS) modules, which will be distributed among the four FCS electronic cabinets in each aircraft. Outputs from these flight control modules drive Honeywell actuator control electronics units. The same operating system is also used by Airbus for the A400M military airlifter avionics computers, as well as those of the A380.

The Honeywell-developed FBW flight control system is a step beyond that of the 777, which was Boeing’s first airliner to be designed with an electrically signaled control system. “We’ve taken all the lessons learned from the 777 and applied them to the new aircraft, as well as taking advantage of the FBW technology that we didn’t fully do with the 777,” says Sinnett.

The 787 system is “full authority” acting in vertical as well as lateral axis, and is designed to help reduce the structural weight of the outboard wing (by shifting the lift distribution inboard using manoeuvre load alleviation control laws to move ailerons, spoilers and flaperons). “We lower the weight by bringing down the loads on the structure and we get a 4,000lb [1,800kg] reduction out of the box. Overall we’ve taken several thousand pounds out of the fuselage and tail by reducing the manoeuvre loads they’ll see in service,” he adds.

The actuation for the primary FCS is being provided by Moog, which is also supplying the control system for the spoilers and horizontal stabiliser. The shipset includes 30 actuators and control electronics, as well as rotary actuation components for the Smiths-supplied high-lift system. The system is designed to provide vertical as well as lateral gust-suppression, helping smooth the ride quality in turbulence. “The idea is the aircraft never responds inertially, but instead the systems sense the pressure differential and dampen it out. The bottom line is the aircraft will move 2ft [60cm] up and down instead of 6ft – and that will improve how you feel, because motion like that is at the same frequencies that cause airsickness,” Sinnett says.

Flight tests to prove the 787 flight control laws have been undertaken using a leased American Airlines 777-200ER dubbed the CV/RR (control verification/risk-reduction) testbed. The flight tests, which include simulation of the 787’s drooped ailerons, have also been used to test out a drag-reducing feature called the trailing edge variable camber (TEVC) function. The tests did not include mechanical modifications to the baseline 777, but are restricted solely to tests using the CV/RR’s specially adapted flight control system. “We can validate these concepts by varying the trailing edge surfaces,” says Sinnett. The tests also include evaluation of the modified software to simulate the increased wing twist angle of the 787, which is designed to shift lift distribution inboard, helping to reduce overall structural weight and improve efficiency.

Boeing says the TEVC could cut cruise drag and save the equivalent of 340-450kg in weight, and takes advantage of the all-new wing and flight control surface design. The fully automatic system, which will be the first practical commercial application of an in-flight variable camber concept, will operate by deflecting the trailing edge flaps in 0.5° increments while in cruise.

Although the 777 CV/RR tests are effectively mimicking the effect of the trailing-edge movement, the motion on the actual 787 surfaces was driven in the flight tests by an electric power drive unit integrated with the torque-tube-driven flap actuation mechanism. While the TEVC control unit will add an estimated 36kg, Sinnett says Boeing predicted that a “0.4-point count in drag reduction” will convert into roughly 450kg of saved weight. The system will be capable of moving the trailing edge through a 3° arc, with the trailing edge being set up and down by as much as 1.5° either side of a neutral setting position.

Tests to date using the 777 have already proven the value of the testbed by uncovering several issues with the initial versions of the 787 flight control software, says Sinnett. “We found problems we hadn’t expected, and some we did expect,” he adds. “It’s been a great tool for validating the concept, and we’ve got to the point where we’re going into the flight-test programme with the right set of control laws.”

Collision avoidance

Warning of turbulence and bad weather will be provided by a suite of sensors in the Rockwell Collins integrated surveillance system (ISS), the heart of which is the WXR-2100 MultiScan weather radar. The ISS, housed in two identical cabinets for redundancy, combines the functionality of not only the weather radar, but also the TCAS, Mode S transponders and the Honeywell-supplied terrain awareness warning system (TAWS). Green Hill’s Integrity-178B and Multitool suite is also being used on the “traffic module” element of the ISS.

 
The common core system is the heart of the 787's open-architecture system avionics

The ISS is “in integration testing here in Cedar Rapids”, says Rockwell Collins’ Irmen, adding “we have successfully performed simultaneous operation of functionality”. The ISS-2100 Power PC-based processor at the heart of the system is backed up by a support ASIC for the “traffic” functionality of the TCAS. With the TAWS, Irmen says, “Honeywell is performing the initial testing in Redmond, Washington and shipping units to Mel­bourne, Florida, for integration testing. Honeywell has participated in this testing in Florida.”

The Multiscan weather radar has been undergoing flight testing and “late this fall, we will begin airborne testing of the WXR-2100 with the ISS-2100”, says Irmen. “We will deliver the flight test hardware this fall/winter without full functionality. Software loads will be provided with a gradual functionality build-up,” he adds. The first flight test units will be delivered in November, with initial production units following the month after.

Rockwell Collins is also supplying the communications system based on the VHF-2100 radio, which is software upgradeable to VDL Mode 3. Providing room to upgrade to accommodate future CNS/ATM (communications, navigation, surveillance/air traffic management) applications, the radio system is designed to use 20% less power and weighs around 30% less than contemporary systems. The comms suite also includes the SAT-2100 satcom and integrated HIST-2100 high-speed terminal enabling dual-channel Swift 64 data communications at up to 432Kbits/s. The system will accommodate up to three voice and two data channels simultaneously.

The company is also providing the dual, standard head-up-displays for the 787 which are based on the head-up guidance system line developed by Rockwell Collins’ Portland, Oregon-based group (formerly known as Flight Dynamics). Dubbed the HPU-2200 and HCU-2200 (left and right units respectively), “they are a completely new development”, says Irmen. “The 787 HUD provides situation awareness out of the window. It will not provide landing guidance,” he says, adding that a new feature will be take-off guidance. The first unit has been delivered to Boeing’s integration test site, and initial production hardware will be delivered to Spirit in February.

The Honeywell supplied-navigation suite includes the flight management system, air data system, dual integrated navigation receivers (INR) and inertial reference system (IRS). Back-up systems include attitude heading reference systems for the IRS, as well as standby, mini-IRS units. The suite also includes DME receivers, optional ADF radios and dual radar altimeters, while the INR has a fully integrated package consisting of a Category IIIb-capable instrument landing system (ILS) or Cat I GLS (global landing system) This is made up of a GPS/GLS landing system, as well as more conventional VOR and ILS functions. ■

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