Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
push" approach (described in Section 7.5). Aircraft range has increased from the B707 era
(~5,000 nm) to today's long-range (~8,000+ nm) aircraft such as the A340 and the B777.Longer
range flights will need to take account of additional passenger amenities such as sleeping
facilities. There is little doubt that operational pressures will ensure that existing baseline designs
will continue to be developed to achieve further increases in range and payload. Average aircraft
size has increased steadily over the transpacific region over the past 20 years, with an
associated rise in the numbers of passengers. This route and North Atlantic routes are expected
to increase in the future (see Figure 7-3) (Boeing, 1996). For domestic travel, however, shorter
range designs with a larger payload can provide benefits in fuel efficiency.
7.2.3. Time Scales from Technology Development to End of Service Life
The rates at which new aircraft designs and derivatives of current products enter the commercial
fleet vary across the range of aircraft size and missions. Progress in airframe and engine
technology has an important effect on the time scales over which aircraft mature; so do
economic and customer requirements. The implementation of improved technology is limited,
however, by the number of opportunities arising for new aircraft projects or major derivatives of
existing designs. In some cases, improvements are introduced singularly. In others,
combinations of improvements are introduced. Thus, in one case a new airframe might utilize an
existing engine (DC-10/CF6-50), whereas in another a new engine might be applied to an
existing airframe (A310/JT9D and PW4000). In some cases, changes are at the component
level, the B757-300 using the RB211-535E4 LEC (low emissions combustor) engine and the
A320 using the CFM 56-5B(DAC) (double annular combustor). The B777/GE90, on the other
hand, represents an example of an all new airframe/engine/combustor technology combination.
There is a considerable period of time between the start of a preliminary design of a new or
derivative aircraft and the delivery of that aircraft to a "launch" airline. This period includes
extensive testing and certification of new equipment. Production rates and aircraft life cycle then
determine the time that the aircraft series will remain in the fleet.
A typical time-history for a medium-range commercial aircraft from technology development to
the end of airline service life would be as follows:
i. Technology development preliminary/final design through aircraft certification testing = 5-
10 years
ii. Successful production run = 15-20 years
iii. Aircraft lifetime = 25-35 years
iv. Total time span (i) through (iii) to retirement of aircraft series = 45-65 years
v. Time span (ii) through (iii) to retirement of aircraft series = 40-55 years
7.2.4. Summary of Aircraft Fuel Efficiency Improvements
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Figure 7-2: Transport aircraft cruise altitude progress
Figure 7-3: Average airplane size.