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Systems for Green Operations (SGO)


Systems and their associated technologies account for a small proportion of an aircraft's overall weight, yet their role in enabling optimised aircraft operations, increasing safety and efficiency, and reducing environmental impact - is disproportionately significant.

The Systems for Green Operations (SGO) is an Integrated Technology Demonstrator (ITD) focused around the development, refinement and integration of technologies that pave the way towards the greening of aircraft operations.

Reductions in CO2, NOx and noise emissions are achieved mainly through reduced fuel consumption and optimized flight trajectories.

The SGO ITD contributes to a reduction of the environmental impact of aircraft operations in two major areas:



  • Management of Trajectory and Mission (MTM) by implementing optimised and environmental friendly flight trajectories
  • A more efficient Management of Aircraft Energy (MAE), an integrated approach to the design of the aircraft systems with a view to reaching higher overall energy efficiency




The SGO ITD delivers technology solutions, systems and components that are integrated at aircraft level, demonstrated in realistic operational conditions, and proven against the stringent requirements set by end users and airframe manufacturers.


Major Demonstrators

Technologies developed for - and within - the ITDs are used to test and validate mature systems and system architectures using both flight testing and ground-based hardware test rigs. Examples of this include:

  • thermal and electrical benches for energy
  • operational labs for trajectory and missions


The major ITD demonstrations are:

  • Ice detection and ice protection: Flight tests on an Airbus test Aircraft in Q4 2015
  • Electrical Environmental Control System (E-ECS) flight tests on Airbus Aircraft in Q4 2015
  • Flight tests of Liquid Skin Heat exchanger in Q4 2013
  • Ground tests of Integrated Electrical technologies (starter generator, power distribution, electrical load management, etc) at the Airbus PROVEN test bench in Q1 2014
  • Ground tests of thermal load management systems in AVANT test facility in Q1 2015
  • Ground test in an Airlab simulator of mature Flight Management functions for various flight phases in Q2 2015
  • In flight validation of Time and Energy managed descent in Q3 2015

In addition, SGO delivers a number of technology prototypes for integration and demonstration in other ITDs:

  • Delivery to Eco-Design of starter-generators, Power Electronic modules, power rectifiers, etc.
  • Delivery of test equipment to Green Regional Aircraft (generators and associated conversion units, E-ECS for flight test, etc)
  • Delivery of Swash Plate actuation to Green Rotorcraft in Q1 2015




Research and work are divided into five work packages. Each has a specific research area. The 5 WPs are:

  • Aircraft solutions and definition of exploitation strategies (WP1)
  • Management of Aircraft Energy (WP2)
  • Management of Trajectory and Mission (WP3)
  • Large Scale Demonstration for Large Aircraft Application (WP4)
  • A/C level assessment & exploitation (WP5)


Breakdown structure:




  • Thales
  • Liebherr

Other members

  • Airbus
  • Alenia
  • Fraunhofer
  • Rolls-Royce
  • Saab
  • Safran



The Associates of Clean Sky are industrial companies, including several SMEs, research centres and universities. The Associates involved in SGO are the following:

  • Dielh Aerospace
  • DLR
  • Selex ES
  • GSAF (a cluster composed of : Cranfield University, NLR, Aeronamic, TU Delft, University of Malta)
  • University of Nottingham
  • Zodiac Intertechnique


SGO has identified R&T activities that require expertise or resources not currently available in the consortium. SGO Partners are therefore involved in the programme via Calls for Proposals, and they intervene to address specific topics, challenges and issues.

Key competencies sought cover a wide range of areas. Here are a few highlights:

  • Simulation, modelling and analysis of electrical networks
  • Cooling technologies
  • Materials with high mechanical resistance for rotating machines
  • Mathematical expertise in multi-parameter optimisation
  • Aviation operational expertise (pilots, airline experts, etc.)

Since 2010, numerous additional partners (currently more than 60) have joined the SGO team.


Potential applications

The SGO ITD is currently in its last year of execution, hence no further partners are sought. Future opportunities will arise in the frame of CS2 SYS-ITD, the follow-up to the SGO-ITD.


Expected benefits

The current environmental targets for large aircraft and for a typical reference mission are: 


All-Electrical Aircraft


SGO One of the most familiar sounds on an aircraft – one that disconcerts many a nervous flyer – is the whirr and clunk as the hydraulic system retracts the wheels after take-off or extends them as the plane comes in to land.





SGO But in years to come, that sound could be a thing of the past as hydraulic and pneumatic systems of the aircraft - that have traditionally been powered by diverting power from the engines - move to running on electricity.

 While there is little prospect of aircraft actually being propelled by electric motors any time soon, there is a move within the industry to run all other power systems on electricity.



Illustrations: pneumatic (in red), hydraulic (in blue) and electric (purple) power generation today (top left) and in the future (bottom right)


Current situation and challenge

In today's aircraft, a small proportion of the power generated by the engines is, on one hand, mechanically diverted (via the gearbox) to electrical generators, central hydraulic pumps and other subsystems. On the other hand, engine high pressure bleed air is used to pneumatically power the air-conditioning system, anti-ice and other systems.

As for the Auxiliary Power Unit (APU), it provides both pneumatic power for air-conditioning and electrical power to the aircraft's avionics systems, to cabin and aircraft lighting, to the galleys, and other uses such as the entertainment systems mainly when the aircraft is on the ground. The hydraulic pumps transfer hydraulic power to the actuation systems for primary and secondary flight control, to landing gear and to a number of ancillary systems.

How does Clean Sky address this challenge

In Clean Sky - the PPP (Public Private Partnership) between the European Union and Europe's aviation industry that is working on making future aircraft more environmentally friendly - "conventional equipment systems on civil aircraft are a product of decades of development by the systems suppliers. Each system has become more complex, resulting in an architecture that is far from being optimal. Designers have striven to overcome the myriad of interactions between equipment by increasing the efficiency of each system in an evolutionary way."

There comes a point when we reach the limit of refining and tweaking old systems, where there is simply no more efficiency to squeeze out – and we have to employ radically new technological approaches, especially as the latest generation of aircraft demand far more electrical power than their predecessors were designed for. The societal pressure to deliver this extra power without impacting the environment and the quest to reduce fuel consumption – are all drivers of significant technological step- change.

To illustrate the point…

The Airbus A380 (now over a decade in service and with a capacity of almost 600 passengers) uses 0.8MW of electricity while the Boeing 787 (introduced into service in 2011 and carrying between 242 and 330 passengers depending on model and configuration), consumes 1.5MW - a big increase compared to the fleet which has been in operation for many years now, including the A320 or A330.

Improving the architecture by, for example, correctly choosing the power offtake location, improving the gearbox integration and in some cases removing it, reducing engine bleed, introducing local hydraulic power sources and switching to electrically powered solutions, could substantially reduce the amount of power derived from the engines and therefore improve fuel efficiency.

Current hydraulic systems generate constant power. This means that excess power is sometimes generated but not used, resulting in a waste of fuel. The use of electric power for all non-propulsion requirements on an aircraft will enable power to be used only when it is needed, while getting rid of the hydraulics will not only reduce weight but also reduce pollution because there will no longer be any hydraulic fluid to dispose of.

 The use of only one power source (electric) instead of currently three (electric, hydraulic, pneumatic), leads to efficiency improvements due to less conversion losses; electrical systems tend to be more efficient, easier to control and require less maintenance than their hydraulic and pneumatic counterparts.

The future is here already

Boeing's new B787 Dreamliner is the most advanced current aircraft when it comes to electric systems, using bleed-air power only for the engine inlets' anti-ice system. The transition to electric architecture has drastically reduced the aircraft's mechanical complexity, the airframe manufacturer says. "Overall, the B787 will reduce mechanical systems complexity by more than 50% compared to a 767."

The B787 "reflects a completely new approach to onboard systems," the company says. "Virtually everything that has traditionally been powered by bleed-air from the engines has been transitioned to an electric architecture." The affected systems include engine start; APU start; wing ice protection; cabin pressurisation and hydraulic pumps.

The no-bleed architecture does not just improve the efficiency of the engines, it also improves reliability and cuts maintenance costs, Boeing claims. By eliminating the pneumatic systems from the airplane, the B787 will realise a notable reduction in the mechanical complexity of airplane systems.


Fuel cells and hydrogen

Apart from the engines, what other additional electrical power source is available? In the near term, the kerosene powered APU could be powered by less expensive fuels such as gas or diesel, but looking further into the future, fuel cells could play a major role in powering on-board systems.

Airbus last year linked up with Parker Aerospace to explore the possibilities of replacing APUs with fuel cell systems, which could cut fuel consumption by 10-15% on short-haul flights. The APU gets more use in short-haul flights because aircraft spend more time on the ground than on long-distance routes.

The fuel cell is a proven technology that has demonstrated its effectiveness in other applications, notably the Apollo space programme. However, complexity, cost and safety issues around the hydrogen and oxygen that fuel cells need to produce electrical power must be taken into account.

There is a lot of research going on into how hydrogen can be stored on board. The only waste products from fuel cells are water, heat and oxygen depleted air, which can all be reused on the aircraft (the oxygen-depleted air in flight safety systems) further reducing weight and fuel consumption.

While the first fuel cells used on aircraft would be single centralised units, over time, as the technology evolves, there are likely to be a number of smaller, decentralised units deployed to those areas that use the most power, such as the galleys and air conditioning.

Challenge for the future

One challenge for the all-electric aircraft is that at the same time as this transformation is going on, fuselages are being built with increasing amounts of composite materials. These do an excellent job of making aircraft lighter, but they do not have the conductivity of traditional metal fuselages so a lot more wiring will be needed in future aircraft.

Further into the future, Airbus envisages aircraft that are harvesting energy from a range of sources to reduce the amount of fuel they need – including solar power and the heat from passengers' bodies, from the galley and the air-conditioning system.