FOCUS N°3The eleCTriC AirCrAFT

DGAC-DMF5032 / July 2011

FUel TANk PrOTeCTiON AgAiNST igNiTiON…

…A MilitAry HeritAge

Dassault Aviation has produced about 6,000 military aircraft, including the world-famous Mirage family and Rafale.The Falcons are developed and manufa ctured by the very

same teams that develop and manufacture their military brothers.Therefore, the state-of-the-art, demanding design, technologies and processes needed to produce fighters are within the genes of all Falcons.

01

PrePAriNg The FUTUre, The everlASTiNg ChAlleNge!

T he air transport community has always been seeking technological progress that will optimize the economical andoperational performance of aircraft. Throughout history, from

the introduction of the jet engine up to today’s Digital Flight Control Systems and advanced flight decks, periodic breakthroughs have provided amazing progress in air transport performance and safety.Once again, the aeronautics’ community is asking for new breakthroughs to face the challenge of aviation’s sustainable growth, and the growing aspiration for flexible and efficient transportation with little or no impact to the environment.Already scientists and engineers are working on new and innovative technologies for the future generation of aircraft. Some very large initiatives like Clean Sky in Europe and Cleen in the U.S. are joining aeronautics’ research forces to prepare the next aircraft generation, and make the future a reality!The Electric Aircraft is one of technology’s potential routes towardstomorrow’s aircraft. This is the subject of this third Technology Newsletter.

The aircraft engines are the originating source of power for the aircraft, both for thrust and for onboard power to drive vehicle systems and utilities.

Substitution of the fuel as the energy source is very questionable: conventional jet fuel has unbeatable energetic performance per unit of mass & volume.Engine performance will greatly be improved thanks to innovative configurations and advanced integration, but will still use thermal combustion to transfer energy from fuel to thrust!

Therefore, the energy revolution of the Electric Aircraft (and this Tech Newsletter) exclusively focuses on a promising way to power vehicle systems and utilities.

Electric

Hydraulic

Pneumatic

ENERGY

+Today Tomorrow

+

Electric

owow

Hydrau

Pn

Electric Aircraft’s final objective is to power all air vehicle systems (except engines) by electricity, whereas conventional architecture is relying on three different power modes: electrical, hydraulic, pneumatic.

Even being the best in class for energy per mass, hydrogen has a very low density which makes it a bad candidate to fuel the aircraft’s engines. It would require very large tanks!

03

The CONCePT

Commercial and business aviation is likely to continue using turbine engine propulsion and conventional jet fuel.But propulsion is not the only energy need within aircraft.

A conventional architecture requires energy in three different forms to drive the aircraft systems and utilities: electric, hydraulic and pneumatic.The hydraulic and pneumatic power systems have been operational for decades and are today extremely efficient, reliable and safe. The related technologies have come to complete maturity and some say that further improvement would be minimal.

Significant gains may not be achievable via the continuous improvement of existing systems on conventional architectures. Any further improvement requires the introduction of radical architectural changes and the exploitation of new, different technologies.The quick progress of power electronics and electrical motors technologies looks promising, and should provide the bulk of innovative architectures in the future.

The Electric Aircraft concept proposes to use these new technologies in order to replace the conventional hydraulic and pneumatic systems by electrically-driven systems. The objective is to achieve new optimums for the energy transfer and use for vehicle systems by taking advantage of the efficiency, flexibility and maintainability that electrical energy offers.

Dassault Aviation is therefore actively involved in technology developments to see if, and how, such new architectures could deliver their promises of a more efficient aircraft. Of course, this is a long-term perspective.

In a conventional architecture, the overall power supply is the sum of contributions from 3 individual systems: pneumatic, hydraulic, electric.This involves the addition of power peaks which normally do not occur simultaneously. Using a single power source allows the designers to address these different requirements with a dramatically reduced power capability. All the more, using a single, flexible and efficient energy medium such as electricity should allow better energy usage.

energy MAnAgeMent

Total Power Capability Total

Power Capability

Average Power Supply

Average Power Supply

Electric

Hydraulic

Pneumatic

Simplification with a single form of energy, combined with electricity's flexibility allows optimization of energy usage

The energy usage is optimized and variation in power demand is less chaotic.

In the conventional architecture the average power supplyis about 7 times smaller than the total power capability.

In an all electric architecture the ratio between average power supply and power capability could drop to roughly 2.

05

OPTimize The eNergy CONSUmPTiON

Electric Aircraft technologies introduce radically new energy management and new energy usage strategies:

• Better energy transfer and better efficiency of electrical devices reduce the total energy consumption;

• Reduction of installed power capability, suppression of ducts, pipes and liquids lead to an overall system weight and size decrease;

• Rationalization and stabilization of system energy offtakes allows a more efficient use of the engines;

• The absence of hydraulic fluid suppresses the risk of harmful environmental leakage and simplifies maintenance.

Nevertheless, achieving such improvements requires significant technology progress before electrical components could positively compete in size and weight against their well-proven, highly-optimized similar counterparts in a conventional architecture.

The technology quest has started ...

(

Engine APU Engine

Air Conditioning

Air

Anti Icing

PneumaticStarter

ElectricGenerator

StarterGenerator

ElectricalDistribution

FCSActuators

UtilitiesActuators

ElectricalStarterGenerator

Avionics

FCS computer

VehicleManagementSystem (VMS)

VehicleManagementSystem (VMS)

HydraulicPump

FCSActuators

Oil Electric

UtilitiesActuators

ElectricalDistribution

Battery

Air Conditioning

Anti Icing

Fuel Cells

Avionics

FCS computer

HydraulicDistribution

FROM A TRADITIONAL ARCHITECTURE TO A SIMPLE INNOVATIVE ARCHITECTURE

07

SimPliFy The ArChiTeCTUre

Besides creating an innovative perspective to improve aircraft efficiency, Electric Aircraft will deliver additional and significant operational benefits to the user.

• The design is simplified. Some volumes are reduced, some circuits are totally removed. Flammable hydraulic fluids and high temperature ducts are eliminated, relaxing some design constraints, and simplifying segregation design rules. New design optimums may be reached, with positive impact such as improved manufacturing cycle, reduction of parts count, weight, fuel consumption, ...

• New designs will benefit from the intrinsic qualities of electricity for smarter failure management. Additional redundancies and new reconfiguration strategies will serve failure tolerant operational modes, increasing the dispatch level.

• The maintenance is eased and reduced: - Electrical components can be easily removed and replaced in a

“Plug & Play” fashion,- Simplification of the architecture and suppression of hydraulics

facilitates the maintenance, with a reduced diversity of tasks and ground support equipment,

- Electrical based technology facilitates pooling of resources,- The absence of hydraulic fluid eases safety regulations associated

to maintenance personnel and the related manipulation of hazardous materials,

- Built-in test and continuous health monitoring will be generalized, providing accurate real-time diagnosis and prediction of impeding failures, meaning less downtime.

09

A rAdiCAl TrANSFOrmATiON

Introducing Electric Aircraft is not a simple question of replacing some equipment by electrical devices. It requires the comprehensive revisit of the onboard energy management, distribution and usage. All vehicle systems are impacted due to the new intrinsic performances, new modes of operations and new interactions.

The Sub-System The Transformation The Technological Challenges

Engine • Thrust is still conventionally produced by thermal combustion• The only form of offtake is dedicated to electrical generation

• Engine redesign for bleedless architecture

Power Generation • Electricity becomes the unique onboard energy • Electrical start of engine• Large increase of electrical power generation capacity• Robustness against power demand fluctuations and rapid power surges• Electricity storage• New failure management philosophy

Distribution • High power is distributed all over the aircraft. The electrical network becomes multi-voltage and may accomodate power regeneration

• Multi-voltage connection & distribution• High versatility with brutal connection or disconnection of loads and multiple

transients (connectors & filters)• Increased electrical network pollution (harmonic distortion)

Actuation • All actuators (flight control, doors, landing gears, brakes …) are electrically driven

• They can generate electricity in reverse operating mode

• High torque, High power density• New dynami c behavior (displacement control, loads, over travel stop …)• Intallation into wing & airframe

Air Conditioning • An electrically driven compressor replaces the engine bleed of high pressure and hot air

• Energetic efficiency

De-/Anti-Icing • Electrical heating carpet or vibrating devices replace hot air circulation in the leading edges

• Energetic efficiency

Engine accessories • All accessories are electrically-driven • Energy balance

The Common technological Challenges • High voltage• Thermal management• Electro Magnetic susceptibility / Robustness to lightning strikes• Density & compactness• Reliability

The Eco-Design Thermal Test Bench at Fraunhofer Institute will allow testing of full-size Falcon airframe sections, equipped with innovative electrical systems, in specific environment typical of cruise altitude.

Prototypes of electrical systems developed by SGO will be tested on the Eco-Design platforms.

The Copper Bird Test Bench was completed in 2005 at Hispano- Suiza. Capable of comprehensively simulating a high voltage electrical network for a business jet, it will accomodate the integration and testing of a wide range of equipment.

Two Integrated Technology Demonstrators (ITD) within Clean Sky are related to the Electric Aircraft:• Systems for Green Operation (SGO) to address individual electrical systems technologies with higher power/weight ratios;• Eco-Design concentrating on cleaner onboard energy architectures & systems.Dassault Aviation is responsible for Eco-Design in partnership with Fraunhofer Institute, a German research organization.

tHe europeAn green initiAtive: CleAn Sky

Launched in Brussels in February 2008, Clean Sky is a European Joint Technology Initiative (JTI) dedicated to the future of green airplanes and air transport, for which Dassault Aviation is a key partner.This program plays an essential role in developing breakthrough technologies and concepts

from 2010 to 2015, for incorporation on Falcon business jets starting in 2017.Key figures: CO2 emissions reduced by 50% and perceived noise by 50% by 2020; €1.6 billion; 86 organizations in 16 countries.

tHe FrenCH green initiAtive: CorAC

In addition to its involvement in the European Clean Sky program, Dassault Aviation is an active partner to the Civil Aviation Research Council, or CORAC. The council was created in France in July 2008 to support an ambitious research & technology strategy intending to control the environmental footprint of air transport by 2020.

The council proposes technology developments for the Electric Aircraft with programs such as:

• GENOME: to address the electrical innovative technologies (High Density Generator, Power Electronics, Distribution Center, High Voltage Storage and Control, Diphasic Cooling, Fuel Cells, Electrical Actuators …)

• AFUE3: focus on electrical actuation for landing gear including new functions such as electrical taxiing.

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CleAn Sky & eleCtriC AirCrAFt

011

whAT iS dASSAUlTdOiNg?

A global perspective from the aircraft designer is mandatory to efficiently support the design choices for tomorrow’s aircraft.

It will be based on:• Comprehensive trade-off analyses with multiple scenarios of

technology insertion;• Deep understanding of integration issues and system

interdependences;• Strong safety analysis and anticipation of relevant certification

processes.

For that purpose, Dassault Aviation is pursuing R&D activities, throughout internal studies and cooperation programs, focusing on two main objectives:• I nvestigate innovative architectures and qualify evaluation &

design tools;• Give realistic & quantified performance and calendar objectives

for R&D actions.

These activities are mainly supported by the European Clean Sky and French CORAC Initiatives.

tHe eleCtriC AirCrAFt: All SySteMS involved in A globAl ApproACH

Anti-Icing

High PowerStarter Generator

New Secondary Power Systems

Multiple VoltageHigh Integrity, Regeneration Compatible Electrical Network

Distribution Centers, Connectors, Converters, Filters, Power Electronics

ElectricalActuation

Electrical Pack & Cooling

Electrical BrakeAdapted Engines

013

wOrkiNg TOwArdeleCTriC AirCrAFT

Aviation history has been marked by dramatic progresses. Yet, the run for progress is not a steady journey, and often comes via technological breakthroughs. It is where we stand today with vehicle systems. Traditional systems are totally mature, and therefore, there is little potential for major improvements

unless we encounter another technological breakthrough along this progress path. Today, vehicle systems are made of three separate - but locally optimized - power sources: pneumatic, hydraulic & electric. Within these three power sources, only electricity has the potential to replace the others, and will allow a global rationalization and optimization of the entire system.

This increased role for electricity sounds promising as it would open the way for better fuel efficiency among other benefits. One of these benefits would be a reduction in the overall demand of the available power supply needed, thanks to a better energetic efficiency and a better ratio between the full capability and the average use. Another benefit of the electric aircraft would be a lighter jet through a global systems weight and size decrease. It would also be more environmentally friendly due to the elimination of toxic fluids thus preventing harmful leaks and handling of hazardous materials.Finally, the maintenance would be eased and the reliability improved, thanks to the general simplification and standardization of the system architecture.

Although the concept is available, there is still significant work to do in reducing the weight and size of electric devices before they could compete with their conventional counterparts. Due to the critical role of the existing systems, steps are necessary before reaching the goal of fully merging the hydraulic, pneumatic and electric systems into a single electric system. Fortunately, some electric elements have already been designed, built and flown, such as the Falcon 7X slat actuators, and a secondary rudder actuator.

Once these electric technologies are developed and refined, the Electric Aircraft may become a reality. Yet, the global integration of the different elements into a single system requires the expertise of aircraft manufacturers. Dassault Aviation is in the front line, not only with the design of some parts, but also with a continuous R&D effort through international cooperation – as CORAC or Clean Sky - where it paves the way toward the Electric Aircraft. Therefore, future Falcons will always be at the leading edge of technology to keep offering their operators the smartest way to do business.

A1

APPeNdix: FOCUS ON SeleCTed TeChNOlOgieS

The Electro-Mechanical Actuator (EMA) uses electric motors to directly drive the screw through a mechanical gearbox. For activating primary flight control, the EMAs are likely to use high voltage (e.g. 270 VDC). Power electronics components and electrical drive architectures are key enabling technologies. Weight, size and cooling are major issues for the EMA integration into the thin wing of a business jet.

The Electro-Hydrostatic Actuator (EHA) uses a reversible, electrically driven pump motor to directly load self-contained hydraulic fluid to a piston. Hydraulic fluid drivesthe rod in the same fashion as a standard hydraulic actuator. The EHAs have then a similar dynamic behaviour, and can achieve high torques.Contrary to the EMA, the EHA has internal hydraulics. It still then keeps part of the drawbacks of hydraulic actuation, for example maintenance duties, environmental concerns, or leakage risks. Once mature, an EMA could be lighter, smaller, and less complex than an equivalent EHA because of the absence of a local hydraulic loop.

Drive power from actuator controler

Electro-Hydrostatic Actuator (EHA)

Electro-Mechanical Actuator (EMA)

Reversible pump-motor

Rod

Drive power from actuator controler

Gear box

Motor

Piston

Screw

A3

APPeNdix 1: eleCTriC ACTUATiON

Availability of a reliable, efficient electrical actuator is a must on the technology roadmap toward the electric aircraft. To suppress hydraulic circuits, flight control actuators will use

electrical power to induce motion to the control surfaces. Such actuators shall deliver high torque to activate a primary control surface loaded by a high speed aerodynamic wind, with a high dynamic response, moving the surface from up to down in less than a second.

Dassault Aviation is the only business jet OEM who designs, develops and manufactures the whole flight control system of its products: architecture definition, control laws design, software development and validation, hardware design, development and manufacturing. Dassault Aviation is also pursuing continuous R&D efforts to develop future generations of actuators. Current developments apply in particular to future high efficient EMA flight controls.

Boeing X-45 UCAV features an Electrical Architecture with EMA for control surface actuation as well as for weapon bay and landing gear doors actuation. Even for military aircraft, the use of EMA to actuate primary systems is limited to demonstrators, such as this unmanned vehicle.

A progreSSive introduCtion

With the A380, Airbus has introduced EBHA (Electrical Back-up Hydrostatic Actuators = EHA for Flight Control system redundancy), in case of total failure of the 2 independent main hydraulic circuits.

Electro-Hydrostatic Actuation is now a credible, safe alternative to a third hydraulic circuit. However, the benefit of one hydraulic circuit removal is offset by several penalties: review of power generation and electrical network, actuator weight increase, physical integration…

The advantage of EBHA is not systematic and is in fact very dependent on the overall architecture trade-offs and failure management philosophy.

The Falcon 7X is a compact aircraft compared to other Ultra Long Range aircraft. Its tri-engine configuration is adapted to the integration of a fully independent third hydraulic circuit.

…A MilitAry HeritAge

A5

Dassault Aviation developed and flight tested an EMA as a source for secondary rudder actuation. Although not used on the production of the Falcon 7X, this was achievable since the rudder’s response rate and deflection are limited compared to the wing’s main control surfaces.

EHAs actuate the spoilers on the Falcon 7X. To optimize the wing’s internal layout and mass distribution, the piston housing (left) and the electrically driven hydraulic generator (right) are separated. Implementing a segregated actuation chain for the spoiler offers an additional safety level. Electrical actuation of the spoilers allows to control the aircraft in case of a very hypothetical triple hydraulic failure.

Suppression of the hydraulics implies the use of electrical actuation for all mobile parts originally actuated by hydraulics, including landing gear doors and brakes. Dassault Aviation participated in a study sponsored by the French Defense Procurement Agency to prototype an electrical brake. Cross discipline knowledge is strong between the military and the civilian domains for the development of the Electric Aircraft.

Fuel Cell’s working principle relies on the direct conversion of a substance’s chemical energy into electrical energy. The related electrochemical reaction involves a set of two specific compounds forming an “electrochemical couple”, typically hydrogen and oxygen. It takes place within a cell which consists of two electrodes (the anode and the cathode), that are separated by an electrolyte. On the anode side, the hydrogen molecule H2 dissociates into H+ ions, which go through the electrolyte, and e- electrons, which supply power to an electric load. On the cathode side, the oxygen molecule O2, the H+ ions and the electrons recombine to form water.

This particular energy conversion principle yields two major benefits: a very high efficiency (up to 60% compared to a mere 35% for an internal combustion engine) and a very positive impact on the environment, as the only by-products of the reaction are electric energy, heat and water.

In reality, the cells are stacked up together to form a fuel cell stack, whose supply power capability depends on the number of cells and their unit surface area. By adjusting these two parameters for a specific need, the fuel cell technology can, by design, cover a large range of power, from a few Watts up to several MWatts.

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A7

APPeNdix 2: FUel CellS, A very Old iNNOvATiON

The first fuel cell ever constructed was tested as early as 1839. But the technology seems to have been forgotten until its use in the US space programs in the 1960’s. In fact, it was really

in the mid-1990’s that it started to become the subject of a renewed interest among a wide community of stakeholders (manufacturers and users, research centers, universities, governments, investors…).The interest for this technology has been growing stronger ever since.A huge variety of applications may then be foreseen, as illustrated by the thousands of prototypes which have been tested around the world in the last two decades (may they be for cars, buses, scooters or battery chargers…). The main application for aircraft is to replace the APU which generates electricity onboard when engines are off. Fuel cells will enable a true zero emission ground operation.Additionally, it could provide in flight secondary power, for example to complement the main power generation to cope with irregular, unusual and short peaks of power demand, or to ensure back-up.

However, as of today, there is still some significant progress that needs to be achieved in order to make this technology viable for everyday usage, and especially for aerospace applications: cost reduction, power density enhancement and life cycle improvement among others. And beyond the current limitations of these intrinsiccharacteristics, another issue remains to be tackled in a global manner: the issue of large scale production, storage of hydrogen and distribution into the aircraft at the airport …

Some Dassault Aviation prospective studies: lay-out analysis to accommodate fuel cells and hydrogentanks in a Falcon aft section.

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NOTeS

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