Turns - P-8680030

CHAPTER THREE

T-6A CONTACT

Remember, when an aircraft is flying straight and level, the total lift is acting perpendicular to the

wings and the earth. As the aircraft is banked into a turn, the lift becomes the resultant of two

components. One, the vertical component, continues to act perpendicular to the earth and

opposes gravity. The other, the horizontal component, acts parallel to the earth's surface and

opposes centrifugal force cause by the turn. These two lift components act at right angles to each

other, causing the resultant lifting force to act perpendicular to the banked wings of the aircraft.

This lifting force actually turns the aircraft.

When applying aileron to bank the aircraft, the depressed or lowered aileron (on the rising wing)

produces a greater drag than the raised aileron (on the lowering wing). This increased aileron

drag tends to yaw the aircraft toward the rising wing, or opposite to the desired direction of turn,

while the banking action is taking effect. This is called adverse yaw. To counteract this yawing

tendency, rudder pressure must be applied simultaneously in the desired direction of turn. This

produces a coordinated turn. After the bank has been established in a theoretically perfect turn in

smooth air, all pressure on the aileron control may be relaxed. The aircraft will remain at the

bank selected with no further tendency to yaw since there is no longer a deflection of the

ailerons. As a result, pressure may also be relaxed on the rudder pedals, and the rudder allowed

to streamline itself with the direction of the air passing it.

In all turns in which a constant altitude is to be maintained, it is necessary to increase the AOA

by applying back elevator pressure. This is required because the lift produced to equal the weight

of the aircraft and the centrifugal force caused by the turn must be obtained from the wings to

maintain altitude. The production of lift (and thus back stick pressure) must be increased as

AOB increases and then subsequently decreased as the aircraft is rolled back to level flight.

While rolling out of a turn, adverse yaw (now acting in the same direction as the turn) must be

overcome by the coordinated application of rudder. The yaw effect will often be more apparent

when rolling out of a turn than rolling into a turn.

To understand the relationship between airspeed, bank, and radius of turn, remember the rate of

turn at any given airspeed depends on the amount of sideward force causing the turn; that is, the

horizontal component. The horizontal lift component varies in proportion to the amount of bank.

Thus, the rate of turn at a given airspeed increases as the AOB is increased. On the other hand,

when a turn is made at a higher airspeed for a given bank angle, the centrifugal force of the turn

causes the radius of the turn to be larger.

The inherent positive stability of the T-6A wing has an effect on the manner in which it turns.

Turns in the T-6A may be divided into three types: shallow, moderate, and steep. Briefly, if a

shallow AOB turn is established and the controls released, the aircraft tends to return to level

flight, although this may not always occur due to friction in the control surface rigging. In a

moderately banked turn, if the aileron and rudder pressures are released, the aircraft will tend to

stay at the established AOB. In a steep turn, the aircraft will tend to increase bank. The actual

amount of bank for each type is undefined and varies with changes in airspeed and configuration.

3-6

FUNDAMENTAL CONCEPTS