For a Greener Aviation

The next-generation aero engines (PurePower and LEAP-X) are illustrative of the environmental pressures that are here to stay and indicate that existing aero engines can be expected to be replaced by entirely new designs for most segments of power plants for aircraft

Notwithstanding the cyclic economic downturns, aviation is an industry which is assured of growth trends globally. Paradoxically, the more it grows, the more it attracts the opprobrium of environmental groups, governments and in recent time, nation groups such as the European Union (EU) manifest in its Emission Trading Scheme (ETS) that has raised concerns all across the non-EU civil aviation world. Demand for more affordable aircraft and environmental issues such as tightening emission, noise and climatic change regulations, legislation and pressures, will oversee and temper the growth of aviation in the years to come. Both economics and environment impinge on aircraft design in respect of airframe and aero engines, the latter having greater potential for producing gratifying results to meet the environmental criteria.

Regulatory Oversight

Aircraft are required to meet the environmental certification standards adopted by the International Civil Aviation Organisation (ICAO). These are contained in Annexure 16 (Environmental Protection) to the Convention on International Civil Aviation which comprises two volumes: Volume I - Aircraft Noise and Volume II - Aircraft Engine Emissions. These certification standards have been designed and are kept up to date in order to respond to concerns related to the environmental impact of aviation in the vicinity of or away from airports. The ICAO’s Committee on Aviation Environmental Protection (CAEP) has been assigned the task of setting certification standards for aircraft noise and engine emissions. The CAEP has undertaken an effort to establish medium- and long-term environmental goals relating to the three problem areas such as noise, NOx and fuel burn, as far as aero engines are concerned. In addition, assessments of environmental improvements expected from operational initiatives in the medium- and long-term are also under way. This process is being led by panels of independent experts to ensure transparency and involvement of all stakeholders with the ultimate aim of providing reasonable targets for the aircraft industry.

The ICAO has been reasonably effective in dealing with matters related to operations, safety and security but on the environmental front, it has not been very successful in affecting changes in the policies of member states. The reason is that national politics tends to override environmental issues, especially as perceptions of nations in different stages of development differ considerably.

A good portent is the agreement reached in July 2012 over a metric system that will be used to define global CO2 standards for new commercial aircraft. There are ICAO environmental regulations in place for aircraft noise and NOx emissions but developing a standard for CO2 emissions was proving to be a challenge for CAEP since being tasked to do so in 2010. The agreement by states and observer organisations comprising the CAEP includes factors which account for fuselage geometry, maximum take-off weight and fuel burn performance at three different cruise conditions and paves the way for adoption at the ICAO Council in late 2013.

Parallel to the ICAO endeavours to quantify environmental measurables, aero engine manufacturers have been working on designs more likely to meet the increasingly stringent environment criteria. The most significant segment is the narrow-body aircraft, single-aisle, 100 to 180 passengers, as the civil aviation industry expects that 70 per cent of all new commercial aircraft in the next 30 years will come from that category. Also, since singleaisle aircraft land and take off with greater frequency than twinaisle aircraft, they generate more revenue from maintenance and retrofitting services which represent the industry’s mainstay.

New Technologies

During the recent Air Show at Farnborough, Pratt & Whitney (P&W) announced a contract between P&W and India’s largest low-cost carrier (LCC) IndiGo Airlines to provide PW1100G-JM PurePower, also referred to as the geared turbofan (GTF) engines for IndiGo’s A320neo. IndiGo has 150 A320neo aircraft on order and is one of the earliest customers for the aircraft which is expected to enter service in 2015. According to P&W, the PurePower engine is a leapfrog technology that promises 16 per cent better fuel burn, lower carbon emissions and a 50 per cent reduction in noise. Unlike typical turbofans, a GTF turbofan has a gear box that allows the engine intake fan to turn independently of the low-pressure compressor and turbine, producing the same thrust with fewer aerofoils.