CHAPTER IV — MAXIMUM LIFT & STALLING

The wing area required for a given application is in­fluenced largely by the maximum lift and stalling char­acteristics of the airfoil sections used. Because of the possibility of mishaps in the event of stalling, the factors effecting the maximum lift and stall of wings arc of great importance. The stalling characteristics of airfoils also affects the design of helicopter rotors as well as other types of propulsive devices.

The maximum lift of a wing is defined as that value obtained when a further increase in the section angle of attack gives zero or a negative increase of lift. An airfoil can have two or more values of maximum lift but general­ly only the first is of importance. A wing is said to stall when as a result of a further increase of the angle of attack there is a loss of lift.

The maximum lift of a wing depends on parameters such

as:

• Airfoil section shape

• Operating conditions such as Mach number ;md Rey­nolds number

• Wing planform, and twist

• Auxiliary devices such as flaps, slots, etc.

• Influence of the fuselage and propulsion system

• The type of application; that is, fixed wings, helicopter rotors, etc.

The absolute magnitude of maximum lift in the case of – res is generally not as important as the type of stall •intered. A wing with very high maximum lift can. W – vhptly, losing a major portion of its lift fee: a small ;e in angle of attack above stall with dangerous ‘іГ mences. Such a wing would not be as useful for “Tr‘ w – a wing, having a lower C^* with a more gentle 1 b – s maximum lift and stalling are of primary im – Pwe in the application of wings and airfoils. In this chupwr only the characteristics of straight wings and swuie cement airfoils will be covered in detail; items such as nau. slats, sweep and low aspect ratio wings and their mimenw w maximum lift will be discussed in chapters V,

VI ana XVI.