Optimisation of aircraft ground operations to reduce airport emissions can reduce resultant local air quality impacts. Single engine taxiing (SET), where only half of the installed number of engines are used for the majority of the taxi duration, offers the opportunity to reduce fuel consumption, and emissions of NOX, CO and HC. Using 3510 flight data records, this paper develops a model for SET operations and presents a case study of London Heathrow, where we show that SET is regularly implemented during taxi-in. The model predicts fuel consumption and pollutant emissions with greater accuracy than previous studies that used simplistic assumptions. Without SET during taxi-in, fuel consumption and pollutant emissions would increase by up to 50%. Reducing the time before SET is initiated to the 25th percentile of recorded values would reduce fuel consumption and pollutant emissions by 7–14%, respectively, relative to current operations. Future research should investigate the practicalities of reducing the time before SET initialisation so that additional benefits of reduced fuel loadings, which would decrease fuel consumption across the whole flight, can be achieved.

The Clean Sky Joint Undertaking is currently managing two large-scale research and innovation programmes under FP7 and Horizon 2020 to contribute to the strengthening of the European aeronautical sector ensuring global leadership and competitiveness. This paper describes the research and demonstration programmes in Clean Sky (2008–2017) and Clean Sky 2 (2014–2024) related to propulsion technologies for the next-generation aircraft. The bulk of this work is addressed in Clean Sky 1 under the “Sustainable And Green Engines” (SAGE) programme and under the “ENGINES” programme in Clean Sky 2. The High-Level Objectives are described for each engine architecture as well as the targets in terms of CO2 and noise reduction versus a year 2000 reference unless stated otherwise. An overview of the new engine concepts that would satisfy the ACARE objectives is presented, including the main technologies which are to be developed to ensure the successful demonstration of each of those new engine concepts.

Vertical profile inefficiency caused by low-level flight segments during arrival and departure operations has a great impact on the financial cost of operators as well as negative environmental effects. In this regard, continuous descent and climb operations for arrival and departure phases are mostly preferred as one of the methods that reduce or eliminate vertical profile inefficiencies. In this study, focus is put on the arrival phase and the purpose is: (i) to analyse the vertical profiles of arrival traffic at Mugla Milas-Bodrum Airport (BJV), Antalya Airport (AYT) and Ankara Esenboga Airport (ESB) and to characterise the level-offs that occur in the arrival phase and (ii) to quantify the potential time, fuel and emission savings in the event of a shift of inefficient low-level flight segments to the cruise segment of equal distance. For the purpose of this paper, real-time flight data is used for the analysis of the vertical profiles of flights. Flight parameters, such as latitude, longitude, altitude, speed and so on are used to determine, visualise and characterise level-off segments. The Boeing Fuel Flow Method 2 is used to calculate emissions at any altitude. Analyses of the results show that 80%, 74% and 69% of arrival traffic at BJV, AYT and ESB, respectively. were exposed to at least one level-off lasting longer than 20 seconds and significant potential for time, fuel and emissions savings exist for three airports.

Supersonic civil aircraft present a unique noise certification challenge. High specific thrust required for supersonic cruise results in high engine exhaust velocity and high levels of jet noise during take-off. Aerodynamics of thin, low-aspect-ratio wings equipped with relatively simple flap systems deepen the challenge. Advanced noise reduction procedures have been proposed for supersonic aircraft. These procedures promise to reduce certification noise levels, but they may require departures from normal reference procedures defined in noise regulations. The subject of this article is a take-off performance and noise assessment of a notional supersonic business jet. Analytical models of an airframe and a supersonic engine derived from a contemporary subsonic turbofan core are developed. These models are used to predict take-off trajectories and certification noise levels. Results indicate advanced take-off procedures are helpful in reducing noise along lateral sidelines.

The historical trends of reduction in fuel consumption and emissions from aero engines have been mainly due to the improvement in the thermal efficiency, propulsive efficiency and combustion technology. The engine Overall Pressure Ratio (OPR) and Turbine Inlet Temperature (TIT) are being increased in the pursuit of increasing the engine thermal efficiency. However, this has an adverse effect on engine NOx emission. The current paper investigates a possible solution to overcome this problem for future generation Very High Bypass Ratio (VHBR)/Ultra High Bypass Ratio (UHBR) aero-engines in the form of an Inter-stage Turbine Burner (ITB). The ITB concept is investigated on a next generation baseline VHBR aero engine to evaluate its effect on the engine performance and emission characteristics for different ITB energy fractions. It is found that the ITB can reduce the bleed air required for cooling the HPT substantially (around 80%) and also reduce the NOx emission significantly (>30%) without penalising the engine specific fuel consumption.

The Lean Direct Injection (LDI) combustor is one of the low-emissions combustors with great potential in aero-engine applications, especially those with high overall pressure ratio. A preliminary design tool providing basic combustor sizing information and qualitative assessment of performance and emission characteristics of the LDI combustor within a short period of time will be of great value to designers. In this research, the methodology of preliminary aerodynamic design for a second-generation LDI (LDI-2) combustor was explored. A computer code was developed based on this method covering the design of air distribution, combustor sizing, diffuser, dilution holes and swirlers. The NASA correlations for NOx emissions are also embedded in the program in order to estimate the NOx production of the designed LDI combustor. A case study was carried out through the design of an LDI-2 combustor named as CULDI2015 and the comparison with an existing rich-burn, quick-quench, lean-burn combustor operating at identical conditions. It is discovered that the LDI combustor could potentially achieve a reduction in liner length and NOx emissions by 18% and 67%, respectively. A sensitivity study on parameters such as equivalence ratio, dome and passage velocity and fuel staging is performed to investigate the effect of design uncertainties on both preliminary design results and NOx production. A summary on the variation of design parameters and their impact is presented. The developed tool is proved to be valuable to preliminarily evaluate the LDI combustor performance and NOx emission at the early design stage.

A Lean Premixed Prevaporised (LPP) low-emission combustor with a staged lean combustion technology was developed. In order to study cold-flow dynamics in the LPP combustor, both experimental tests using the particle image velocimetry (PIV) to quantify the flow dynamics and numerical simulation using the commercial software (FLUENT) were conducted, respectively. Numerical results were in good agreement with the experimental data. It is shown from the observation of the results that: there is a Primary Recirculation Zone (PRZ), a Corner Recirculation Zone (CRZ) and a Lip Recirculation Zone (LRZ) in the LPP combustor, and the exchanges of mass, momentum and energy between pilot swirling flow and primary swirling flow are contributed by the velocity gradients, and the shear flow is transformed into a mixing layer exhibiting the higher Reynolds stresses, which suggests the mixing process is strictly affected by the Reynolds stresses.

The semi-analytical prediction of pollutants emissions from gas turbines in the conceptual design phase is addressed in this paper. The necessity of this work arose from an urgent need for a comprehensive model that can quickly provide data in the conceptual design phase. Based on the available inputs data in the initial phases of the design process, a chemical reactor network (CRN) is defined to model the combustion with a detailed chemistry. In this way, three different chemical mechanisms are studied for Jet-A aviation fuel. Furthermore, the droplet evaporation for liquid fuel and the non-uniformity in fuel-air mixture are modelled. The results of a developed augmented modelling tool are compared with the pollutants data of two annular engine's combustors. The CRN results have good agreement with the actual engine test rig emissions output. In conclusion, the augmented CRN has shown to be efficient in predicting engine emissions with a very short executing time (few seconds) using a small CPU requirement such as a personal computer.

The present experimental work highlights the acoustic far field and flow field characteristics of confined co-axial swirling pipe jets. Co-axial confinements with six vanes at angles of 0°, 20° and 40° are considered here. Two pipe lengths of L/D=0.5 and 2 are studied. The Mach numbers studied range from 0.85 to 1.83. An increase in the pipe length causes suppression of the transonic tones in non-swirl pipe jets. Swirl reduces the low frequency noise components and increases the high-frequency components compared to non-swirl jet. The broadband shock associated noise is mitigated by the swirl pipe jets. However, the screech tone is completely eliminated by the swirl pipe jets. Further, swirl pipe jets radiate low levels of noise at all the emission angles compared to non-swirl pipe jets, for both the pipe length cases at supersonic Mach numbers. Increase in the pipe length enhances the shock associated noise and OASPL for the non-swirl pipe jet. Centreline pitot survey and schlieren visualisation show a reduction in core length, reduction in the number of shock cells, weakening/destruction of the shock cells by the swirl pipe jets compared to the non-swirl pipe jets.

Aviation brings great commercial and social benefits and, as the global economy develops, the demand for air transport is expected to grow. However, aviation also contributes to climate change and there is increasing international pressure to limit mean global temperature rise. Therefore, the future success of aviation is likely to depend upon the industry's ability to hold its environmental impact within politically acceptable limits. This paper describes aviation's interaction with climate and sets out, in broad terms, the challenge facing the industry. The prospects for mitigating the adverse effects by advanced technology working through aircraft design and manufacture are assessed and some potential restrictions imposed by airport infrastructure are identified. Some consideration is also given to the practicalities imposed by airline economics and the likely impact of the recent ICAO regulations, plus the proposed global-based market measures scheme for aviation carbon offset. It is argued that the environmental problem is not just about carbon dioxide emissions and that aircraft technology improvement alone is unlikely to provide a complete solution. The observation that, in current operations, the total fuel used is almost twice the minimum required suggests a need to recognise a broader ownership of the problem and broader responsibility for the solution. However, improvements in the overall system efficiency will probably need to be driven by additional regulation and the imposition of other financial measures.

The overall conclusion is that the actions currently being taken and currently being proposed are probably not sufficient in themselves to meet the challenge of climate change. However, it appears that there is more that can be done and, provided that action is taken soon, there are some grounds for optimism that aviation will still be able to meet the needs of society in the 21st century.

Fuel consumption in flight is dependent on three main factors—the aerodynamic efficiency of the aeroplane, the thermal efficiency of the engine, and the efficiency of navigation, which entails a study of the most advantageous height, speed and direction of flight under any conditions of wind. Fuel consumption is therefore the ultimate measure of the overall efficiency of the complete aeroplane, the pilot, and the organisation ; its complete study would require far more time than can be given to it in a single lecture. I propose, therefore, to confine myself to fairly general considerations, with particular reference to the commercial aeroplane. There have been distinct advances in the direction of fuel economy in flight since the war period, but even now the weight of fuel carried in a commercial machine operating over the comparatively short London-Paris route of 230 miles and capable of a cruising speed of 100 miles per hour is approximately half the full paying load carried, so that a reduction of the fuel load by 40 per cent., which is by no means outside the range of possibilities, would increase the paying load by 20 per cent., other things being equal.

The 855th Lecture to be given before the Royal Aeronautical Society, “ Fuel Systems for Turbine-Engined Aircraft ” by Mr. J. E. Walker, A.F.R.Ae.S., was read under the auspices of the Luton Branch of the Society on the 24th April 1952 at Luton.

Steven Ford was omitted from the list of authors in the article by Murrieta-Mendoza(1). The correct authorship is:

A. Murrieta-Mendoza, R. Mihaela Botez and S. Ford

The article has now been updated with the correct authorship; this change has been made to the online version only.

To ensure meaningful evaluation and prediction of configuration and flight effects on aircraft noise generation and propagation, reliable representation and measurement of relevant aerodynamic flow conditions as well as of acoustic characteristics must be possible. Acoustic wind tunnels, with models mounted in a quiet test section airstream surrounded by an anechoic working chamber, have now been established as primary tools for noise-model research work and should next be exploited also for the direct support of specific quiet aircraft projects. The special advantages of such tunnels in ensuring a more sheltered and controlled environment than outdoor mobile-model facilities and flight testing include capability of continuous operation, repeatable test conditions, high productivity, good measurement accuracy, testing flexibility, and the precise alleviation of reflections from neighbouring surfaces. Of course the recent experience on noise testing under forward speed conditions and on associated techniques is still very limited at both model scale and full scale, as compared with extensive and continuous aerodynamic testing over half a century. However, many of the problem areas associated with subsonic tunnel design and application for noise-model testing, as identified over five years ago, have now been clarified. Also, the special treatments or limitations involved have become quantifiable in many respects, as discussed later under the convenient main headings of tunnel test section requirements (section 2), tunnel circuit design (section 3), special measurement and analysis techniques (section 4) and model scale simulation (section 5).

Aeroplanes are often noisy, and sometimes smelly. Some of them also produce smoke. The purpose of this paper is to attempt an assessment of these and other forms of environmental pollution, also to consider the engineering and administrative measures which are being taken to control them. But before embarking on the subject one must try to put the matter in perspective. As I see it, the threat to the environment does not just come from aeroplanes, transport systems, factories or advancing technology. It comes from man.

For the past 50 years civil air transport has been dominated by the combination of the gas turbine and the B-47 airframe configuration. Both these machines owed their creation to WW2 and both represented revolutionary concepts at the time. Oyer the years, the engine and the airframe have undergone considerable detailed refinement. The changes have resulted in very impressive improvements in performance. However, it is now very clear that both are close to some well defined asymptotic limits that bound their performance. The result is that further potential improvements are smaller in percentage terms, become harder to achieve technically and, consequently, come at increasingly higher cost.

A hugely successful global industry has developed around this standard configuration. Increasingly, more and more companies use aircraft and, as their businesses grow, the demand for aircraft and air transport increases. However, the ability of the environment to absorb this growth is beginning to be questioned and new ideas are required if aviation is to be regarded as an unbounded and a truly sustainable activity.

I am defining the airport facilities as the strength of its pavements and the sophistication of its passenger and baggage loading and aircraft handling provisions.

To illustrate the effect of pavement strength on design, I have taken two representative sizes of aircraft, 50 000 lb (23 Mg) and 300 000 lb (136 Mg) AUW, and shown in Fig. 1 the effect on undercarriage volume of meeting various values of load classification number (LCN) with appropriate variations of tyre pressure and wheel spacing. The smaller machine has twin wheels while the larger has a four-wheel, twin-tandem bogie. The advantage to the designer of being able to work to a high LCN lies not only in the reduced undercarriage stowage volume, but undercarriage weight itself is saved if the wheels can be closely grouped together.

Increasing mechanisation and population densities in our society, coupled with higher standards of living and education, have in recent years resulted in a growing concern about pollution and its effects on the environment. The era of sporadic individual complaints to government is being rapidly superseded by one where strategic concerted action by irate citizens’ interest groups is becoming commonplace. As a result, governments are becoming increasingly involved with the problem of environmental pollution; in Canada, for example, the Environmental Protection Service of the Department of Fisheries and the Environment for fiscal year 1976–77 had a staff of approximately 800 and a total budget of $22 million.

The problem of aircraft noise has been touched on by a number of today's speakers, but I wonder how much it is appreciated that probably the biggest single interface problem before the aviation industry today is that of environmental pollution.

The dilemma which every Minister responsible for civil aviation has to face is how to strike a right balance between, on the one hand, economic and operational considerations and, on the other, the protection of the public from excessive noise. Successive Ministers have indicated very clearly to the Department that they favoured paying a substantial price, if required, for the preservation of amenity.