Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
8.3.5. Summary of Other Operational Factors
Aviation passenger mobility efficiency is very dependent on the type of aircraft, the configuration, the load factor, and the distance flown. Old aircraft use much more
fuel per passenger-km than new aircraft of similar size. The fuel efficiency of different aircraft is examined in Chapter 7. The required energy per passenger-km is in the
range of 1.0 to 3.0 MJ per passenger-km, or about 30 to 110 g C per passenger-km. Airlines have generally optimized energy use per passenger-km, largely because
of economic pressures and the requirement within the industry to minimize operational costs. Thus, with or without environmental considerations, market and cost
considerations are drivers for airlines to optimize the utilization of an aircraft as much as possible.
CO2 intensity for rail transport also depends on factors such as energy source, type of locomotive, and load factor, and emissions of CO2 range between < 5 and 50 g
C per passenger-km. However, a passenger's choice of mode of transport is based on fares, total trip time, and frequency-not just environmental considerations.
ECAC (1996) estimates that less than 10% of the European air passenger travel could be replaced by high-speed train. Yet the scope for substitution is greater in
Europe than in many other parts of the world.
Other operational factors to reduce aircraft fuel burn include optimization of cruise speed, reduction of tankering, reduction of additional weight, and energy savings at
the airport such as limitations on the use of APUs and reduced taxi times. The total potential reduction in fuel burn by further optimization of these factors is in the
range of 2-6%. The relative contribution of each factor is indicated in Table 8-6.
Finally, aircraft noise mitigation measures such as operational changes and retrofitting of engine equipment on older aircraft to conform with current aircraft noise
standards could have an adverse effect on fuel use. Application of hushkits could lead to an increase in fuel consumption of up to 5%. However, lightweight hushkits
may have a negligible effect on fuel use.
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