Keep It Clean!

When reams of statistics fail to convince, a single number sometimes helps drive home a point. In May, the Mauna Loa Observatory in Hawaii detected for the first time that the concentration of carbon dioxide (CO₂) in the atmosphere had passed 400 parts per million (ppm). This is the figure the Intergovernmental Panel on Climate Change (IPCC) believes could result in a global temperature rise by up to 2.4 degrees Celsius by the end of the century, enough to cause severe environmental and climatic changes.

Apart from a few die-hard sceptics, most experts believe that human-induced climate change is a reality and that the situation could easily spiral out of control unless determined measures are taken to control greenhouse gas (GHG) emissions. Before the industrial revolution and its addiction to fossil fuels unleashed a frenzy of carbon injection into the atmosphere, CO₂ levels were just about 280 ppm. In 2008, James Hansen, one of the world’s foremost climate change scientists, wrote, “If humanity wishes to preserve a planet similar to that on which civilisation developed and to which life on Earth is adapted, paleo-climate evidence and ongoing climate change suggest that CO₂ will need to be reduced from its current 385 ppm to at most 350 ppm.” Yet CO₂ seems set to rise well above 400 ppm.

Where does aviation come in? Aircraft engines emit toxic gases and particulate matter that contribute to climate change and global dimming. They also produce noise. Apart from the direct effects of emissions, flying at altitudes near or in the stratosphere may increase the total climate change impact significantly, perhaps even double it. Overall, it is estimated that aviation is currently responsible for about 3.5 per cent of the warming effect of GHG emissions.

Primarily, there are three ways to limit aviation-related emissions namely using fuel-efficient aircraft, reducing weight and improving operating techniques to burn less fuel. Each year, the aviation industry manages to improve fuel efficiency by about 1.5-2 per cent. But aviation itself grows by up to five per cent thus overpowering these gains. By 2050, aviation’s share of the total emissions could increase to between 5 per cent and 15 per cent.

Ramifications for Regional Aviation

Regional aviation is an important, convenient and often the only way of linking isolated communities with the rest of the world. It generally involves small aircraft ferrying passengers from outlying airports to the nearest major hub where they board airliners that transport them over large distances, perhaps even across continents, to the desired destinations.

By its very nature, regional aviation is more polluting than intercontinental aviation. Small regional jets don’t emit a great deal of greenhouse gas but since they carry fewer passengers, emissions per-seat-kilometre are high. Regional flights are generally over short distances and involve many more take-offs and landings besides more time on the ground with engines running. These add significantly to emissions. In a typical operating day, a regional jet with 50 seats might perform ten cycles of take-off and landing yet cover a total distance of just 2,500 km. During the same period, a jumbo jet with more than 400 passengers onboard may traverse over 12,000 km with just one take-off and landing. The big plane has far lower emissions per-seat-kilometre. However, its effect is somewhat increased because the impact of carbon emissions at high altitude is greater than at ground level.

Regional jets are inherently 40-60 per cent less fuel-efficient than narrow-body planes such as the Boeing 737 and Airbus 320. This is more due to differences in operational patterns like the large number of take-offs and landings and lower cruising levels, rather than any technological inadequacy. As long as the price of oil was low, the inefficiency of regional jets was masked. But around the turn of the century, environmental issues came to the fore and the high emissions of regional jets became problematic.

Around the same time, the price of oil exceeded $35 a barrel. Manufacturers and operators began to realise that the only way to keep costs and emissions under control was to put in more seats, first 70, then 90 and then 100. While Embraer began producing the E-Jet E-170 to E-195 variants with seating capacity ranging from 80 to 122, Bombardier came out with the 70-seat CRJ700, 86-seat CRJ900 and 100-seat CRJ1000. In fact, the 90-seat regional jet has emerged as the smallest economically viable unit of production. That is why the Russian Sukhoi SuperJet SSJ 100-95, which entered service in April 2011, has a seating capacity of 98. Bombardier’s forthcoming CSeries CS300 will feature up to 145 seats, with a high-density variant of 160 seats. Rival Embraer’s proposed E195-E2 will carry up to 132 passengers normally, with a maximum high-density capacity of 144 seats.

Significant reductions in fuel burn and GHG emissions have already been achieved on long-haul wide-body airliners such as the Boeing 787 and the Airbus 380. Equally impressive gains are promised on forthcoming narrow-body planes like the Airbus 320neo and Boeing 737MAX. However, such improvements are more difficult on smaller aircraft like regional jets. Weight savings are also harder to achieve since regional aircraft must be sufficiently sturdy to withstand the rugged conditions of outlying airfields, higher risk of bird strikes and increased chances of impact with servicing vehicles on the ground.

One thing regional carriers can do is switch to turboprops. Jets are faster than turboprops and greatly reduce travel time. But for short flights, say less than 500 nautical miles, the difference in journey time is small while the fuel-efficient virtues of the sluggish turboprop come to the fore. The ATR 72 and Bombardier Q400 NextGen, for instance, burn about two-thirds the fuel of a typical regional jet. They cruise at a much lower altitude, so they spend less time on the thirstiest stage of the journey, the climb to cruise. Their manufacturers claim that these aircraft produce about 50 per cent less CO₂ emissions than equivalent modern regional jets and a fraction of that produced by older jets. Turboprops also operate at lower levels and so they do not create concerns over ozone layer or contrail production. As these aircraft need shorter runways than jets, it allows them to operate from small rural airports. And the noise and discomfort associated with turboprops in the popular imagination have been largely overcome. Advanced turboprop engines like the Pratt & Whitney PW127 and PW150 also seldom need major maintenance. Their health is assured with little more than oil and filter change plus scheduled inspections.

Refining operating techniques is a constant process and can greatly reduce emissions. Regional airlines have an advantage since they fly over less-frequented routes and away from congested airports. They can follow best practices like continuous climb departures, optimal altitudes for reduced fuel burn, and continuous descent approaches at destination.

A Tireless Quest for Efficiency

Increased fuel efficiency, biofuels and route optimisation; all help to reduce the impact of aviation on the environment. But fuel efficiency cannot be improved beyond a point. Aviation technologists are already grappling with complex interdependencies between CO₂, nitrogen oxide (NOx) emissions and noise. They are often forced to make trade-offs among them before taking critical design decisions. The same goes for operational decisions.

In June this year, the International Air Transport Association (IATA) reaffirmed its target of carbon-neutral growth from 2020 and a 50 per cent reduction in net emissions by 2050 from a 2005 baseline. The carbon footprint of any flight depends on the aircraft model, the distance flown, number of empty seats, and the weight of the baggage. Airlines realise that they cannot operate fuel-inefficient planes and remain viable. However, switching to low-emission aircraft is a costly and a time-consuming process. Fortunately, reducing fuel burn and emissions increases profit which incentivises the industry to pursue fuel-efficient options.

Since regional airlines in India are yet to get off the ground, they are ideally placed to learn from the mistakes of others. In most parts of the world, regional carriers started out with small jets at a time when the cost of aviation fuel was low. But they were forced to switch to larger planes or turboprops to keep operating costs under control. India’s prospective regional carriers can select the most fuel-efficient aircraft, use airspace more efficiently and follow an ecologically sound strategy practically from launch.

The Indian Government is keenly interested in improving regional connectivity. About 90 destinations have been identified to be added to the aviation map of the country. Regional carriers may be subsidised to make such operations viable. The government has also decided to set up 51 new low-cost airports in 11 states. New regional airlines will thus be able to take aviation services to areas comparatively free of pollution. Regional airports, however, strain the environment. Often large tracts of forests or fields have to be cleared to make way for runways, taxi tracks and associated facilities. A diligent cost-benefit analysis and environmental impact assessment should be a prerequisite for all new airports. Once the decision is taken to go ahead, measures to preserve the environment or compensate for its destruction, need to be built into the contract.