Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
OEW might be saved. This weight reduction represents approximately a 1% fuel efficiency improvement.
7.3.7.4. Aircraft Systems
"Aircraft systems" is a generic term applied to the large number of subsystems used in a modern aircraft to manage the aircraft in flight. All of these systems offer room
for improvements that could reduce fuel burn. It is estimated, for example, that extending the capability of fly-by-wire control systems to include active pitch stability
augmentation and wing load alleviation offers the potential for a 1-3% improvement in overall fuel efficiency. Development of an "all electric" airplane, which also
deletes the current use of air bleeds from the engines for pneumatic and anti-icing secondary power, has the potential to save fuel during cruise. The use of advanced
technology fuel cells to replace the auxiliary power unit (APU) could provide savings in overall local/ground-level fuel burn and emissions, with the added benefit of
reduced noise near terminals. In some instances, however, the cost and complexity required to overcome failure modes of these systems is high, which may inhibit or
delay their use in commercial service. The use of active center-of-gravity control is another potential means to improve fuel efficiencies at cruise conditions. Flight
safety improvements could increase OEW.
7.3.7.5. Advanced Airframe Concepts
Figure 7-6: MD-11, blended-wing body, and conventional planview size comparison.
Aerodynamic efficiency improvements such as higher lift/drag ratio (e.g., slotted cruise airfoil and
natural laminar flow), new structural materials, and control system advances (such as fly-bywire)
could collectively improve fuel efficiency by about 10%, compared to current production
aircraft. An aircraft representing some of these nearer term (2016) advanced airframe
technologies is shown in Figure 7-5 on the previous page (Condit, 1996).
At the upper end of the airframe size scale (> 600 passengers), a more futuristic concept
approach such as a blended-wing body (BWB) could be developed. A plan view size comparison
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