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More-Electric Aircraft Technologies Move From Paper to Platform; TRW
Well Down the Road In Proving Its More-Electric Systems Capability
SOLIHULL, England--(BUSINESS WIRE)--Jan. 17, 2001--Advances in
aviation technologies are frequently driven by factors like weight
reduction, increased reliability, enhanced performance or life cycle
cost savings. Combine two of those benefits in a single program and
you have a powerful argument for improvement. Put all four together in
one visionary concept and you have an unquestionable mandate for
change.

The ongoing evolution of aircraft electrical design is generating a
new technology roadmap in which major benefits in the areas of weight,
reliability, performance and cost are being combined with increased
onboard power demands to create today's "More-Electric Aircraft"
systems. In addition to their myriad operational benefits both today
and in the near future, these evolutionary programs are also serving
as the critical foundation for a revolutionary longer-term concept
known as the "All-Electric Aircraft."

"The goal of the visionary 'All-Electric' Aircraft concept of the
future is to eliminate as many hydraulic power sources and hydraulic
lines as possible," explains Mike Yates, Chief Engineer for Systems
Integration at TRW Aeronautical System (Lucas Aerospace)(NYSE:TRW).
"And the engine, which is currently required to produce thrust,
pneumatic power, hydraulic power and electrical power, can now be
redesigned and optimized to produce thrust and predominantly
electrical power."

Noting that it will take another 10 to 15 years to develop the
technologies behind the All-Electric Aircraft vision, Yates emphasizes
that there are intermediate steps that can come before that time and
those next steps are taking place right now. Termed More-Electric
Aircraft systems, the intermediate steps involve the evolutionary
application of electrical power systems, electronics and distributed
architectures to simplify much of the current bulk and complexity
inherent in hydraulic and pneumatic aircraft systems. Immediate
benefits derived from the wider application of electrical power and
electronics include performance and reliability improvements as well
as savings in weight, space and overall life-cycle costs.

Taking the More-Electric Aircraft from paper to platform, Airbus
Industrie has base-lined both power-by-wire flight controls and
variable frequency power generation for its new A380 super jumbo. The
A380 will be the next clear platform in which a major technological
change toward More-Electric systems is implemented.

Current advancements surrounding aircraft systems can be grouped into
the areas of flight controls, power generation and management, and
engine controls. In each of these fields, TRW Aeronautical Systems is
unique in its breadth of experience and its depth of knowledge for
current and future applications. Moreover, because of the interrelated
nature of these critical aviation subsystems, TRW's wide-ranging
capabilities provide rare synergistic benefits for present and future
systems integration efforts.

Flight Control Systems
Flight control systems provide several examples of the technologies
supporting the evolution from traditional hydraulic actuation controls
to fly-by-wire and then eventually to power-by-wire to achieve
benefits such as enhanced availability and aircraft maintainability,
and reduced weight and aircraft ground service time.

"We've been involved with flight control systems since the early
days," says Phil Hudson, TRW's Chief Engineer for Flight Controls.
"The control systems were originally hydraulic/mechanical and then
evolved into fly-by-wire designs through the application of digital
computer technology. We were involved in the introduction of
fly-by-wire on the Airbus A320, the first civil application of a
complete fly-by-wire system, and we've also been pursuing electric
actuation over the last 10 years so that we can move even further into
power-by-wire technologies such as Electro-Hydrostatic Actuation (EHA)
including our Integrated Actuation Package (IAP(TM)), and Electro-
Mechanical Actuation (EMA)." [ http://www.e-flight.com/a320.htm ]

Conventional flight control actuation, known as fly-by-wire, is
controlled electrically, but powered hydraulically. These systems rely
on a complicated circuit of high-pressure hydraulics running
throughout the aircraft to supply the hydraulic pressure needed to
move each control surface. The goal of power-by-wire is to
significantly reduce or eliminate altogether the hydraulic connection,
and its associated risks, by providing electrical power straight to
the actuators. These electrically powered flight control actuation
technologies involve a motor and an electronic unit that serves as the
motor controller. However, the electronic unit can also be designed to
serve more functions than simply motor control. It can serve as a
smart actuator controller in its own right and be part of a
distributed control system.

Distributed control is a main TRW technology theme and has potential
for application in flight controls and engine control systems. This
technology puts intelligence local to the actuation elements in a
control system and can substantially reduce harness weight and improve
fault detection and isolation when applied to today's aircraft and
engine systems. TRW's main technology themes of "More-Electric
Aircraft" systems and "distributed controls" can be combined to
achieve the optimum system design.

"You get the benefits of distributed control along with the benefits
of electric actuation and you get those benefits without adding any
major cost because you have to have the electronics there anyway for
local control," says Yates.

The benefits of moving to More-Electric flight controls are
substantial. To put it into context, a large civil aircraft, such as
the A380, would have three channels of hydraulic circuits to ensure
adequate system redundancy. The likely first step is to replace one
hydraulic circuit with a series of electro-hydrostatic actuation,
realizing more than an estimated 1,000 pounds of weight savings, and
increasing the pressure of the two remaining hydraulic channels to
5,000 psi, realizing an additional estimated 1,000 pounds of weight
savings.

Maintenance benefits are also substantial. Power-by-wire actuation
units are line-removable with only mechanical and electrical
connections to the aircraft, which eliminates the need to refill or
bleed systems of hydraulic fluids as is required with central
hydraulics. Since power-by-wire actuators are self contained and
remotely located at the surfaces, the area exposed to damage is
greatly reduced. Additionally, power-by-wire actuators can be designed
as position sensitive, which means that the actuators provide only the
flow and pressure necessary to move and hold the actuator in a desired
position. Conventional central-hydraulic systems are configured to
produce continuous pressure. Flow is metered at each actuator, which
can lead to a large consumption of power and generate unwanted heat.

TRW has been developing these flight control technologies for several
years and has substantial experience in proving these technologies as
they move through the development process. The Company's IAP(TM)
achieved 1,000 hours of in-service flight experience over two years as
part of the U.S. Air Force's Electric Starlifter program. The program
successfully demonstrated the effectiveness and benefits of the
IAP(TM) with systems running on both wings and both flight control
channels providing full roll control authority. No other Company has
gained that amount of proven flight experience on power-by-wire
technology.

TRW has also been developing EHAs for large aircraft as part of the
COVAN (Commandes de Vol Avions Nouveaux or Flight Controls for Future
Aircraft) program. The Company's EHAs have begun initial
flight-testing on an A340 aileron and A320 aileron after having
completed 1,000 hours of pre-flight testing for flight qualification.

The increase in usage of electrical power for primary and secondary
actuation and ultimately replacing pneumatic services on the aircraft
will place demands on the electrical system, both in terms of total
power draw and power quality.

Noting that the next generation A380 large surfaces will require
multiple electrical actuators, Yates acknowledges that, "The electric
power demand will be increased substantially. The generating system
has to be designed to cope with all power demands including multiple
surface transients. Additionally, the actuator motor control is by
short, high-current pulses. So power quality is obviously an issue."

Power Management
Clearly, any change from hydraulic to electric flight control
actuators places increased demands on the aircraft electrical power
generation system. One of the parallel "More-Electric" technology
themes where TRW Aeronautical Systems has addressed these requirements
for power generation and power quality involves variable frequency
generators. Variable frequency generation provides the key to a
higher-output power management system, which increases power without
significantly increasing weight.

Traditional aircraft designs utilize a constant frequency generator
system in which the speed variations of the engine are canceled out
within the generator itself through a complex integrated drive
generator subsystem. The variable frequency design eliminates this
complex subsystem and allows generator output to be variable over the
engine speed range, resulting in significant improvements in both
reliability and maintainability. The first civil jet-engine
all-variable frequency system is now flying on Bombardier's Global
Express(R) business jet.

"We have clearly demonstrated that this system concept enables
successful operations of all the aircraft's systems," says Peter
Crouchley, TRW Aeronautical Systems' Chief Engineer for Electrical
Systems. "In addition to successful operation on Global Express(R),
Airbus has evaluated this technology and has base lined the variable
frequency system for their next-generation A380 aircraft."

The Global Express(R) utilizes TRW's 40 kVA variable frequency
generators. To offer the same benefits to large aircraft, TRW
Aeronautical Systems engineers have targeted higher power capabilities
for variable frequency and are moving swiftly to prove the technology.
The Company's 90 and 120 kVA variable frequency generators have
undergone rigorous testing over the past two years producing excellent
power quality throughout. The 120 kVA unit has already successfully
achieved more than 1,000 hours of accelerated life testing and a 150
kVA generator is currently in development.

Another important issue surrounding power generation involves the
ability to generate aircraft power during emergency situations. TRW is
developing fan-driven generators that could be used to replace
conventional ram air turbine (RAT) designs. In addition to providing
adequate emergency power under windmill engine conditions, the new
design gives the generator the capability to supplement the main
generating system by operating as a main generator over the whole
engine speed range. This capability creates the opportunity to reduce
the size and weight of the other main generators.

"The All-Electric Engine of the future will require electrical power
to be able to operate," explains Yates. "It's vitally important that
we have an element of power which is independent from the rest of the
aircraft and that is available when you need to restart the engines.
This design not only provides emergency aircraft power under windmill
conditions, it also provides the electrical power required to power
the pump that pumps the fuel that gets the engine started. Otherwise
you would not have that engine restart capability, so it's quite
crucial in that respect."

Engine Controls
In addition to their activities surrounding flight control systems and
power generation and management, a significant portion of TRW
Aeronautical Systems' More-Electric Aircraft activities has involved
the evolutionary application of engine control systems.

Jet engine control systems raise the pressure of the fuel to enable
combustion and deliver the required fuel quantity for starting,
accelerating and steady state running the engine at all
engine-operating conditions. Originally the control systems were
fairly simple but became more and more complex as time went on to
incorporate features like altitude compensation and control limiters
for pressure, temperature and speed. This complication in
hydro-mechanical controls mandated the introduction of supervisory
electronics and led to today's digital electronic controls, including
Full Authority Digital Electronic Engine Control (FADEC) systems. TRW
Aeronautical Systems has been in the forefront of these engine control
developments since the early days of flight.

"We produced the Concorde FADEC demonstrator program back in the
1970s," says Brian Farman, Chief Engineer, Electronics. "We went from
hydro-mechanical engine control technology to digital FADEC
technology, which we've been working on for many years now. That was a
major change in engine control technology and we were there on the
first military aircraft that had it. Today, FADEC technology is now
the norm across the industry, and we are working to exploit the step
changes in commercial technologies to reduce size and cost of our
systems, including their application to distributed engine controls."

This step in More-Electric Aircraft design involves incorporating some
electronics in each of the engine actuators and connecting them via a
digital data bus to the network of nodes located around the engine.
TRW has demonstrated a three node distributed engine control system
incorporating a "smart" fuel valve. Embedded in that fuel valve is a
two-channel electronic controller taking fuel flow demand information
from the digital data bus and controlling valve position to the fuel
flow that's required. The application of distributed control
technology will have the added benefit of facilitating fault isolation
with 100 percent certainty, not only improving in-service reliability
but also providing an estimated 20 to 30 percent savings in the cost
of maintenance of that system over a typical engine system.
Additionally, a weight savings of approximately 110 pounds can be
achieved on a large civil engine with a distributed architecture
through simplification of the harnesses.

Slightly further down the "More-Electric" evolutionary path is the
"smart" electrically driven fuel pump. Based on technology that has
already been demonstrated on a 15,000-lb.-thrust engine by TRW
Aeronautical System engineers in collaboration with the Defence
Evaluation and Research Agency (DERA), the smart pump will directly
modulate fuel flow to the engine. The engine control will demand a
fuel flow and the smart fuel pump will adjust to the desired speed,
driving the pump to deliver the required fuel flow and eliminating the
valve in the fuel metering system.

The All-Electric Engine
The benefits provided by the smart electric fuel pump are realized
when used as an enabler for the All-Electric Engine. By reducing the
need for hydraulic, pneumatic, or mechanical power takeoff, the new
engine can be redesigned and simplified to focus on producing thrust
and predominantly electrical power. In addition to obvious reliability
enhancements stemming from the simplified design, theoretical design
projections feature a smaller overall outer shell for a given thrust
range with a corresponding improved drag coefficient.

Having clearly proven the utility of fly-by-wire technologies and
established the technology groundwork for follow-on power-by-wire
applications, as well as variable frequency power generation, TRW
Aeronautical System engineers are looking toward the next major
milestone -- development of the systems and equipment for the
All-Electric Engine.

Bringing it All Together
But even before the "All-Electric" Aircraft concept takes to the
skies, the numerous examples of More-Electric Aircraft technologies
provided by TRW Aeronautical Systems point to the complex interaction
between system requirements of flight controls, power management and
engine controls in More-Electric Aircraft designs. TRW's systems
expertise in all three of these areas enables the Company to be fully
aware of the impact that More-Electric transitions in one of these
areas has in the other and, more importantly, understand the system
integration issues as the industry moves further down the road toward
the All-Electric Aircraft. In the meantime, TRW anticipates seeing
many of its new technologies being proven in commercial service well
before the All-Electric Aircraft vision becomes a reality.

CONTACT: TRW U.S.  Renate Myles, 703/648-0831 or U.K.  Martin Butler,
+ 44-121-451-5975 KEYWORD: DISTRICT OF COLUMBIA UNITED KINGDOM
INTERNATIONAL EUROPE BW2040  JAN 17,2001 4:01 PACIFIC 7:01 EASTERN
[ http://www.trw.com/innovations/tech_firsts/firsts_main.asp ]
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