Wednesday, April 25, 2007

The 787

One of the major sources of emissions into the atmosphere is from air travel. The expansion of air travel has been wildly quick over the last two generations. I went to Europe with my parents in 1975 for the first time and the scope and scale of the travel at time was much smaller than today. The flight was not direct as there was not enough demand. The Airport in Vancouver was 1/4 the size of today. The Calgary airport was almost nothing. Frankfurt Rhein/Main was much smaller.

The planes of the 1970s were much less efficient in fuel usage. In the early 1970s the expectation was still that we would shortly be going to supersonic airplanes such as the Concorde. The thought made sense when one looked at the previous 30 years. In 1945 only relatively small prop transports could cross the Atlantic with maybe 80 passengers in 16 hours - something like the DC 4. By the late 1950s there were jets crossing the Atlantic with 180 passengers and covering 6000 km in just over six hours. By 1970 the 747 was in service with a seating capacity of 370.

Instead of going to the supersonic planes, as everyone thought would be next, the focus over the last 30 years has been on reducing the cost per passenger mile. This has been done by carrying more passengers on planes, owning only one type of plane (such as WestJet and their all 737 fleet), and improving fuel usage. As an example, the 1970 747 used 18.7L/km for 366 passengers and the latest uses 14.6L/km for 466 passengers. That is 300 litres per passenger for a 6000 km trip in 1970 to 188 per passenger for the same trip in the latest model.

The newest Boeing, the 787 will be able to carry 232 passengers on the long range version. It uses about 9.2 L/km - or in terms of the above calculations or 240 litres per passenger for 6000 km. It has a range of over 15000 km.

The other direction is the Airbus A380. It can carry up to 853 people 15 000. A fully loaded A380 would use under 140 litres per passenger for a 6000 km trip. A 737 can not go as far, but its fuel consumption per passenger km is about the same.

Can airplane efficiency be increased faster than the demand for air travel rises? The goal is another 25% more efficient by 2020. As it stands, the most efficient planes are now more fuel efficient than cars when fully loaded. If one assumes the airplane is 70% full, the newest airplanes are still under 4.5L/100 km - roughly the same as a Prius.

Airplanes will remain a major source of emissions, but they are clearly not as bad as cars and seemingly as an industry it would be easier to replace the old with new in a more effective manner than cars.


7.2.4. Summary of Aircraft Fuel Efficiency Improvements

Significant improvements in aircraft fuel efficiency have been achieved since the dawn of the jet age in commercial aviation. Historically, these improvements have averaged 1-2% per year for new production aircraft (Koff, 1991; Albritton et al., 1996; Condit, 1996). These advances have been achieved through incorporation of new engine and airframe technology. Changes have included incremental and large-scale improvements. Examined over several decades, however, they represent a relatively steady and continuous rate of improvement. A similar trend is assumed when fuel efficiency improvements are projected forward to 2050.

Table 7-1:Percentage production fuel-efficiency improvements (ASK kg-1 fuel).
Time Period Airframe Propulsion Total Aircraft
1950-1997 30 40 70a
1997-2015b 10 10 20
1997-2050 25 20 45 (40-50)c

a) To date, approximately 3/7 of the total fuel efficiency improvement of 70% is attributable to advances in airframe technology.

b) Based on improvement records to date and the discussion in Section 7.3.7, it is reasonable to expect an airframe production average fuel-efficiency improvement of ~10% by 2015. This percentage improvement is further substantiated in other reference material (Greene, 1995). Similarly, a 10% propulsion production average fuel-efficiency improvement is considered feasible in this time frame.

c) In the longer term (2050) compared to 1997, a total aircraft production average fuel-efficiency improvement of 40-50% is considered feasible (ICCAIA, 1997g). These levels of efficiency improvement are assumed in the 2050 technology scenarios described in Chapter 9. The ratio of airframe to propulsion production average fuel-efficiency improvement over the period 1997 to 2050 is projected to be 55/45 in favor of airframe technology developments. This is equivalent to a 25% airframe fuel-efficiency improvement.

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