Technology Evaluator (TE)


A unique attribute of Clean Sky is the fact that it uses two complementary techniques for evaluating the aircraft and rotorcraft technologies that are developed in the programme.

The first, which is somewhat conventional, is to evaluate the new technology in comparison with older reference technology, using specific criteria such as weight saving, fuel saving, maintenance or production improvement, overall aircraft system improvement, and noise reduction.

These technology-specific evaluations are performed inside Clean Sky’s ITDs (Integrated Technology Demonstrators) and, depending on the Technology Readiness Level (TRL) achieved, these technologies can graduate from simulations to ground or flight tests.

The second evaluation method is a global evaluation of the environmental benefits (emissions and noise reduction) of the Clean Sky programme. To achieve this, key technologies are clustered into aircraft or rotorcraft simulation models to assess what the performance levels of these aircraft and rotorcraft would be when equipped with Clean Sky technologies. This second type of evaluation is carried out using a specific Clean Sky tool: the Clean Sky Technology Evaluator (TE).


Role and Function

The Clean Sky Technology Evaluator is both a sub-project and an integral part of the Clean Sky programme. In this ambitious European programme, environmentally friendly aeronautical next-generation aircraft and rotorcraft technologies are developed and validated using Integrated Technology Demonstrator (ITD) platforms.

Within the Clean Sky programme the function of the Technology Evaluator (TE) is to assess the environmental impact of these innovative technologies when integrated into concept aircraft and rotorcraft (as defined by ITDs), and to determine the extent of Clean Sky's contribution to ACARE's environmental objectives (for CO2, NOx, noise).


Figure 1: Clean Sky technologies integrated at concept aircraft level


Hence, the TE is a means to show the most efficient combination of technologies integrated at so-called concept aircraft and rotorcraft level and to assess their maximum environmental potential at the air transport system level (global fleet world-wide) and airport level when incorporating these aircraft and rotorcraft into fleets.

Approach & Indicators

In order to forecast the environmental improvement when Clean Sky aircraft and rotorcraft are flying, Clean Sky aircraft and rotorcraft models simulate flights in specific scenarios. It is then possible to benchmark noise and emissions of Clean Sky aircraft and rotorcraft against their reference counterparts (aircraft and rotorcraft which include technologies from the year 2000, ACARE’s baseline year). These scenarios have been segregated into four assessment levels:

  • Aircraft level - a single aircraft/rotorcraft flight
  • Airport level - all aircraft/rotorcraft movements at and nearby an airport
  • Global level - the fleet of aircraft and rotorcraft all around the world
  • Life-cycle level - where the entire life cycle of an aircraft/rotorcraft, from design, to manufacturing and to dismantling, is evaluated

These four assessment levels were defined in order to be able to assess the full extent of Clean Sky's contribution towards the ACARE environmental objectives.

The evaluation results of these levels are generated using dedicated simulation platforms and uploaded in the Technology Evaluator Information System, based on a web-service platform which is available for all Technology Evaluator members.

Aircraft level

Clean Sky technologies are selected and integrated at the aircraft/rotorcraft level into concept aircraft/rotorcraft models by the ITDs. Technologies are then developed in the ITD industry platforms and validated through demonstrators where available. The following technology domains are included:

  • Flight-system technology (e.g. optimised trajectories),
  • Laminar flow wing technologies, and
  • Engine technologies (e.g. open rotor engine)

Scenarios at this level compare Clean Sky and reference aircraft and rotorcraft independently on a single trajectory. Emissions reductions (CO2 and NOx) are calculated and expressed as a percentage for a complete flown aircraft/rotorcraft mission and per available passenger seat. A number of noise measurements are also defined in the process.

Airport level

A number of representative airports are selected and their noise impact and contribution to local air quality is analysed. Noise contours are studied and the human population within these noise contours is determined as well as the contour surface area for given noise levels. Then, realistic airport traffic scenarios are simulated based on existing ATC procedures and airport operations of the respective airports. The environmental impact of an airport traffic scenario with Clean Sky aircraft for a representative day is compared with that an identical traffic scenario using reference aircraft. Traffic scenarios are based on a 2020 fleet forecast, to align with ACARE targets.

Global level

Here the global air transport system is investigated. To evaluate the potential of Clean Sky technologies, a comparison of a 2020 fleet with and without Clean Sky aircraft is performed to quantify CO2 reduction. The environmental impact of a global fleet traffic scenario with Clean Sky aircraft for a representative month is compared with that of the same traffic scenario but with reference aircraft. Traffic scenarios are based on a 2020 fleet forecast, again, in line with the ACARE time-frame.

Life-cycle level

The aim of the assessments at this level is to compare, over the entire life cycle of an aircraft/rotorcraft, the environmental impact in terms of emissions and materials, measured using reference and Clean Sky aircraft/rotorcraft. Because of the complexity and novelty of the approach only three kinds of aircraft and rotorcraft are compared:

  • a short-medium range transport aircraft,
  • a business jet aircraft, and
  • a rotorcraft (helicopter)

The methodology is as follows:

  • First, data is collected for individual parts and processed into an eco-statement for a limited number of representative parts.
  • Then, an upscaling method, based on a breakdown of the aircraft/rotorcraft into modules (such as fuselage or systems) is used to derive from these limited parts the life-cycle analysis of the whole aircraft/rotorcraft.
  • This process is applied to both reference and Clean Sky aircraft/rotorcraft.
  • The difference between the computations provides an estimation of the environmental benefit over the whole life cycle.

Environmental assessments

The evaluation of Clean Sky’s progress towards ACARE's environmental objectives at all four assessment levels (life cycle, aircraft, airport and global) shows extremely encouraging results with regard to the environmental improvement potential in terms of CO2, NOx and noise reductions.

Over the course of the project the level of confidence in the output of the simulations has increased, with both the Technology Readiness Level of the technologies developed by the ITDs and the level of accuracy of the Clean Sky aircraft and rotorcraft models which have been developed by ITDs integrating these technologies. Pending some model updates, the final TE assessment will be carried out by the end of 2016.

Life-Cycle Analysis level

Besides the continuation of upscaling activities from parts to full aircraft, a first comparative life-cycle analysis of a reference part and a Clean Sky demonstrator part was undertaken in 2015. The environmental benefits of the demonstrator part are mainly in areas of weight reduction and reparability.

Aircraft level

The following tables present the summary of the latest Clean Sky TE assessment results (2015) at aircraft and rotorcraft level. These tables are devoted to, respectively, large airliners, regional aircraft and rotorcraft (helicopters).

The Short and Medium Range aircraft (SMR) model included the natural laminar wing and the counter rotating open rotor engine (developed in the SAGE ITD) incorporating the best knowledge Airbus and SNECMA have on the installation, geometry, weights and performance of this platform, and based on latest wind tunnel tests results.

SMR results yielded an average per-available-seat reduction in CO2 of 39-40% and a reduction of 44% for NOx (see Table 1), and an impressive 55% noise area reduction at take-off. Additionally, the SMR aircraft model also includes functionalities from the SGO ITD, such as optimised trajectories in the take-off and landing phases.

The Long Range (LR) aircraft model included an advanced 3-shaft turbofan engine (developed in the SAGE ITD) and the combustor lean burn system, also demonstrated in SAGE ITD. The LR results yielded substantial results, approaching ACARE goals (see Table 1).

The NOx emission computation method outputs are consistent with Airbus and Rolls-Royce expectations for a 2020 advanced turbofan aircraft equipped with the Clean Sky lean burn system. Additionally, the LR concept aircraft model also includes functionalities from the SGO ITD, for instance optimised trajectories in the take-off, cruise and landing phases.      


Table 1: Short/medium and Long Range aircraft TE results in 2015


Table 2 shows the Regional aircraft model results, based on the Concept aircraft of the GRA ITD, showing a very good attainment towards ACARE goals, with 27% CO2 reduction. In particular, the 90 seater concept aircraft is a result of a trade-off activity on the engine performance released from the two engine manufacturers inside the GRA ITD. The 130 seat geared turbofan concept aircraft is a rear mounted configuration as a result of the trade off with the under wing engine installation.


Table 2: Regional aircraft TE results in 2015

The latest rotorcraft assessment, undertaken in 2015, covered the TEM (Twin Engine Medium), the HCE (High Compression Engine) rotorcraft as well as the SEL (Single Engine Light) and TEH (Twin Engine Heavy) rotorcraft.

Table 3 shows the noise and emissions results for Year 2000 Reference technology versus Year 2020 Clean Sky rotorcraft, and the reference configurations are without Clean Sky benefits. Results show relative differences for fuel burn, CO2, NOx and noise ground footprints.  

For example, the deployment of the Year 2020 Concept TEH helicopter configuration may result in reduction in fuel burn and CO2 by 21% and a 55% reduction in NOx - relative to the Year 2000 Reference configuration for a typical mission.

For the TEM assessment, two types of mission were flown: the SAR and fire suppression. For the SEL the passenger transport mission was flown. Some Clean Sky rotorcraft model updates are still expected for the final assessment in 2016.


Table 3: rotorcraft TE results in 2015

Airport level

In the latest assessment (2015) for regional and mainliner aircraft traffic at airport level, five airports were considered to determine potential Clean Sky benefits by comparing a year 2020 fleet scenario with reference 2000 aircraft and a year 2020 fleet scenario with concept (or Clean Sky) aircraft. These airports were two primary hub airports with complex geometry, one primary hub airport with a simple geometry, one secondary hub airport, and one regional airport.

The concept aircraft considered in the appropriate airport traffic scenarios were GRA’s turboprop aircraft and geared turbofan aircraft, and SFWA/Airbus’ short-medium range aircraft and long-range aircraft.

Although not all technologies under development in the Clean Sky ITDs are yet available (i.e. integrated into the concept aircraft models from ITDs) and these ITD aircraft models are not yet all fully matured, provisional results of the calculations for the 2015 assessment at airport level indicate that Clean Sky technologies could bring environmentally beneficial reductions in fuel burn and emissions of:

  • between 40-45% for fuel burn and CO2
  • between 40%-50% for NOx.

Provisional results for noise point to reductions in surface area of noise contours for higher noise levels (i.e. higher than 60 dB(A) Lden) of around 20%. The effect of those noise contour reductions on the population exposed varies per airport, but for most of the airports addressed, the population exposed to the associated noise levels is reduced. Noise reductions at airports range from 15% to 70% - a substantial but expected variance, given the wide-ranging spectrum of parameters and different geometries and topographies between different airports.

Global level

In the latest assessment (2015) at global level, a 2020 global fleet traffic scenario populated with Clean Sky aircraft is compared to the same 2020 scenario populated with 2000-era technology aircraft.

This allows us to determine the Clean Sky benefit at global fleet level in terms of CO2 and NOx reduction. Some assumptions are made for the insertion of Clean Sky aircraft in the fleet. In order to show the full potential of the Clean Sky technologies a theoretical 100% insertion rate is assumed. The concept aircraft considered in the global fleet traffic scenarios were GRA’s turboprop aircraft and geared turbofan aircraft as well as SFWA/Airbus’ Short-Medium Range aircraft and Long-Range aircraft.

Figure 2 shows the example of a 2020 fleet scenario with Clean Sky short and medium range aircraft equipped with open rotor engines, natural laminar wing technologies, and the associated CO2 reduction effect. The latest assessment result (2015) shows that the overall effect of Clean Sky aircraft for mainliners and regional aircraft fleet – including short, medium, long range and regional aircraft – leads to about 20% of CO2 savings per month.

Clean Sky short and medium range aircraft account for 55% of this overall CO2 reduction (see Figure 3). This is linked to the high weighting of this segment in the global fleet, and also to the fact that the Clean Sky programme places less emphasis on long-range, wide-body aircraft.


Figure 2: A Clean Sky short/medium range aircraft fleet scenario and its associated CO2 difference – TE results 2015


The TE consortium is organised as follows:

  • Five Members from Research
    • CIRA (Italy)
    • Cranfield University (United Kingdom)
    • DLR (Germany)
    • NLR (the Netherlands)
    • ONERA (France)
  • All 12 Clean Sky ITD leaders (Airbus, Airbus Group, Airbus Helicopters, Fraunhofer, Alenia Aermacchi, AgustaWestland, Safran, Saab, Thales, Dassault Aviation, Liebherr and Rolls-Royce.)

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