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In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the lift generated by an aerodynamic body such as an aerofoil or aircraft, divided by the aerodynamic drag caused by moving through air. It describes the aerodynamic efficiency under given flight conditions. The L/D ratio for any given body will vary according to these flight conditions.
It is a better measure of the aerodynamic efficiency of an aircraft than the wing aspect ratio. It is defined as: = where is span and is the wetted surface. Illustrative examples are provided by the Boeing B-47 and Avro Vulcan. Both aircraft have very similar performance although they are radically different.
A fixed-wing aircraft increases or decreases the lift generated by the wings when it pitches nose up or down by increasing or decreasing the angle of attack (AOA). The roll angle is also known as bank angle on a fixed-wing aircraft, which usually "banks" to change the horizontal direction of flight.
For conventional fixed-wing aircraft with moderate aspect ratio and sweep, Oswald efficiency number with wing flaps retracted is typically between 0.7 and 0.85. At supersonic speeds, Oswald efficiency number decreases substantially. For example, at Mach 1.2 Oswald efficiency number is likely to be between 0.3 and 0.5. [1]
An elliptical planform is the most efficient aerodynamic shape for an untwisted wing, leading to the lowest amount of induced drag. The semi-elliptical planform was skewed so that the centre of pressure, which occurs near the quarter-chord position at all but the highest speeds, was close to the main spar, preventing the wings from twisting ...
Nonplanar wings: results for the optimal aerodynamic efficiency ratio ε. The parameter ε is the optimal aerodynamic efficiency ratio [25] and represents the ratio between the aerodynamic efficiency of a given non-planar wing and the corresponding efficiency of a reference classical cantilevered wing with the same wing span and total lift ...
A fixed-wing aircraft is a heavier-than-air aircraft, such as an airplane, which is capable of flight using aerodynamic lift. Fixed-wing aircraft are distinct from rotary-wing aircraft (in which a rotor mounted on a spinning shaft generates lift), and ornithopters (in which the wings oscillate to generate lift).
Some early aircraft had fins mounted on the tips. More recent aircraft have wingtip-mounted winglets to reduce the induced drag. [14] Winglets also provide some benefit by increasing the vertical height of the wing system. [6]: 4.10 Wingtip mounted fuel tanks and wing washout may also provide some benefit. [citation needed]