Future Transportation Systems - Decreasing Fuel Consumption and Exhaust Gas Emissions in Transportation - page 276

Table 17.4 Wing aspect ratio depending on flight velocity

Airplanes Velocity

km h -1

Wing aspect ratio
[-] (mi h -1 )

Military fighter 1,800-2,700 (1,119-1,678) 4-6

Reconnaissance 900-1,200 (559-746) 4-6

Airliner 800-1,100 (497-684) 5-10

Transporter 600-700 (373-435) 7-10

STOL a 300-500 (186-311) 7-11

Sport airplane 100-300 (62.2-186) 4-9

Glider airplane 100-300 (62.2-186) 18-30

a

Short takeoff and landing of airplane

strutting, to safely connect with the fuselage. If possible, the wings must be
retractable to enhance the safety of taxiing; see Fig. 17.9 .
Important aerodynamic improvements require further developments for
attaching the fuselage to the wing. The tail unit and the horizontal stabilizers could
be constructed with high vertical size. The optimally insulated engines with low
noise emissions can be placed near the fuselage which can also stabilize the
operation of the airplane [ 39 ].
The aspect ratio of the wing depends on the price of fuel. If the fuel is cheap, the
price of the airplane is decisive and a very small wing aspect ratio is optimal. If the
fuel is more expensive, small fuel savings are also profitable. In this case, man-
ufacturers will build a larger wing aspect ratio which will be bigger than the
optimal size.

17.2.2.4 Blended Wing Body Airplanes

Blended wing body airplanes could be introduced after 2050. Figure 17.10 shows a
model of a blended wing airplane.
The cost of fuel will bring about a radical change in transportation. It is
absolutely not certain whether a blended wing airplane will be developed, even in
the distant future. An earlier introduction could be possible as an air freighter.
However, from an operator's point of view, it is cheaper and simpler to convert a
passenger airplane to being a freight carrier, after 10-15 years of service [ 40 ].

17.2.2.5 Electric Airplane Propulsion

Smaller experimental aircraft already use an electric powered propeller. The wing
span is 13-14 m (42.6-45.9 ft), the empty weight with the battery is 250-300 kg
(551-661 lb), and the motor produces 40 kW (54 HP) [ 41 ].
The battery supplies the engine with 66.6 V for a power of 30 Ah. The lithium-
ion-polymer battery provides 54 cells. The weight is 12 kg (26.4 lb) per cell, which