Editing Wing loading (section)

===Effect on turning performance===
To turn, an aircraft must [[Flight dynamics (aircraft)|roll]] in the direction of the turn, increasing the aircraft's [[Banked turn#Aviation|bank angle]]. Turning flight lowers the wing's lift component against gravity and hence causes a descent. To compensate, the lift force must be increased by increasing the angle of attack by use of up [[Elevator (aircraft)|elevator]] deflection, which increases drag. Turning can be described as "climbing around a circle" (wing lift is diverted to turning the aircraft), so the increase in wing [[angle of attack]] creates even more drag. The tighter the turn [[radius]] attempted, the more drag induced; this requires that power (thrust) be added to overcome the drag. The maximum rate of turn possible for a given aircraft design is limited by its wing size and available engine power: the maximum turn the aircraft can achieve and hold is its ''sustained turn performance''. As the bank angle increases, so does the [[g-force]] applied to the aircraft, this having the effect of increasing the wing loading and also the [[stalling speed]]. This effect is also experienced during level [[Pitch (flight)|pitching]] maneuvers.<ref>Spick, 1986, p. 24.</ref>

[[File:P334a(1).jpg|thumb|Load factor varying with altitude at 50 or 100&nbsp;lb/ft<sup>2</sup>]]
As stalling is due to wing loading and maximum lift coefficient at a given altitude and speed, this limits the [[turning radius]] due to maximum [[Load factor (aeronautics)|load factor]].<!--<ref name=NASA-Maneuverability/>-->
At Mach 0.85 and 0.7 lift coefficient, a wing loading of {{cvt|50|lb/sqft|kg/m2}} can reach a structural limit of 7.33''g'' up to {{convert|15000|ft|m}} and then decreases to 2.3''g'' at {{convert|40000|ft|m}}. With a wing loading of {{cvt|100|lb/sqft|kg/m2}} the load factor is twice smaller and barely reaches 1''g'' at {{cvt|40000|ft|m}}.<ref name=NASA-Maneuverability>{{cite book |url= https://history.nasa.gov/SP-468/ch11-6.htm |title= Quest for Performance – The Evolution of Modern Aircraft |author= Laurence K. Loftin Jr. |publisher= NASA Scientific and Technical Information Branch |date= 1985 |section= Chapter 11. Aircraft Maneuverability}}</ref>

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''. An aircraft with a small, highly loaded wing may have superior instantaneous turn performance, but poor sustained turn performance: it reacts quickly to control input, but its ability to sustain a tight turn is limited. A classic example is the [[F-104 Starfighter]], which has a very small wing and high {{cvt|{{#expr:13166/18.22round0}}|kg/m2|lb/sqft}} wing loading.

At the opposite end of the spectrum was the large [[Convair B-36]]: its large wings resulted in a low {{cvt|{{#expr:119318/443.5round0}}|kg/m2|lb/sqft}} 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 {{cvt|{{#expr:11158/32.42round0}}|kg/m2|lb/sqft}}. The [[Boeing 367-80]] airliner prototype could be rolled at low altitudes with a wing loading of {{cvt|{{#expr:86360/223round0}}|kg/m2|lb/sqft}} 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 <math>v^2/R</math>. This acceleration is caused by the inward horizontal component of the lift, <math>L sin\theta</math>, where <math>\theta</math> is the banking angle. Then from [[Newton's second law]],
<math display="block">
 \frac{Mv^2}{R} = L \sin\theta = \frac{1}{2} v^2\rho C_L A \sin\theta.
</math>
Solving for ''R'' gives
<math display="block">
 R = \frac{2Ws}{\rho C_L \sin\theta}.
</math>
The lower the wing loading, the tighter the turn.

Gliders designed to exploit [[thermal]]s 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. All need low wing loadings.