Wing loading

The lift coefficient is a dimensionless number that depends on the wing cross-sectional profile and the angle of attack.

[12] At steady flight, neither climbing nor diving, the lift force and the weight are equal.

With L/A = Mg/A = WSg, where M is the aircraft mass, WS = M/A the wing loading (in mass/area units, i.e. lb/ft2 or kg/m2, not force/area) and g the acceleration due to gravity, this equation gives the speed v through[13]

So if an aircraft's wing area is increased by 10% and nothing else is changed, the takeoff speed will fall by about 5%.

Likewise, if an aircraft designed to take off at 150 mph grows in weight during development by 40%, its takeoff speed increases to

Some flyers rely on their muscle power to gain speed for takeoff over land or water.

Ground nesting and water birds have to be able to run or paddle at their takeoff speed before they can take off.

For all these, a low WS is critical, whereas passerines and cliff-dwelling birds can get airborne with higher wing loadings.

Turning flight lowers the wing's lift component against gravity and hence causes a descent.

[15] Aircraft with low wing loadings tend to have superior sustained turn performance because they can generate more lift for a given quantity of engine thrust.

The immediate bank angle an aircraft can achieve before drag seriously bleeds off airspeed is known as its instantaneous turn performance.

At the opposite end of the spectrum was the large Convair B-36: its large wings resulted in a low 269 kg/m2 (55 lb/sq ft) wing loading that could make it sustain tighter turns at high altitude than contemporary jet fighters, while the slightly later Hawker Hunter had a similar wing loading of 344 kg/m2 (70 lb/sq ft).

The Boeing 367-80 airliner prototype could be rolled at low altitudes with a wing loading of 387 kg/m2 (79 lb/sq ft) at maximum weight.

Like any body in circular motion, an aircraft that is fast and strong enough to maintain level flight at speed v in a circle of radius R accelerates towards the center at

Gliders designed to exploit thermals need a small turning circle in order to stay within the rising air column, and the same is true for soaring birds.

Other birds, for example, those that catch insects on the wing, also need high maneuverability.

A small wing has less area on which a gust can act, both of which serve to smooth the ride.

For high-speed, low-level flight (such as a fast low-level bombing run in an attack aircraft), a small, thin, highly loaded wing is preferable: aircraft with a low wing loading are often subject to a rough, punishing ride in this flight regime.

Although engines can be replaced or upgraded for additional thrust, the effects on turning and takeoff performance resulting from higher wing loading are not so easily reconciled.

A blended wing-fuselage design such as that found on the General Dynamics F-16 Fighting Falcon or Mikoyan MiG-29 Fulcrum helps to reduce wing loading; in such a design the fuselage generates aerodynamic lift, thus improving wing loading while maintaining high performance.

Aircraft like the Grumman F-14 Tomcat and the Panavia Tornado employ variable-sweep wings.

When the wing is in the forward position takeoff and landing performance is greatly improved.

[17] High lift devices such as certain flaps allow the option of smaller wings to be used in a design in order to achieve similar landing speeds compared to an alternate design using a larger wing without a high lift device.

This may result in beneficial features, such as higher cruise speeds or a reduction in bumpiness at high speed low altitude flight (the latter feature is very important for close air support aircraft roles).

For instance, Lockheed's Starfighter uses internal Blown flaps to achieve a high wing loading design (723 kg/m²) which allows it a much smoother low altitude flight at full throttle speeds compared to low wing loading delta designs such as the Mirage 2000 or Mirage III (387 kg/m²).