Scan Pattern -Cont. - P-330

T-34C CONTACT

CHAPTER FOUR

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

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

the weight of the airplane and the centrifugal force caused by the turn must be obtained from the

wing to maintain altitude. The force of lift must be further increased as the turn steepens and the

centrifugal force builds up, but must be slowly decreased as the airplane is being rolled back to

level flight when completing the turn.

To stop the turn, the wings must be returned to laterally level flight by the use of the ailerons,

and the resulting 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, due to the higher angle of attack and wing loading

which exists when the rollout is started.

To understand the relationship between airspeed, bank, and radius of turn, it must be recalled that

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 angle of bank is

increased. On the other hand, when a turn is made at a higher airspeed for a given bank angle,

the centrifugal force created by the turn becomes greater, causing the turning rate to become

slower with an increase in radius of turn. It can be seen, then, that at a given angle of bank, a

higher airspeed will make the radius of the turn larger because the airplane will be turning at a

slower rate.

The inherent positive stability of the T-34C wing has an effect on the manner in which it turns.

Turns in the T-34C may be divided into three types: shallow, moderate, and steep.

Briefly, if a shallow angle of bank turn is established and the controls released, the aircraft tends

to return to level flight. This may not always occur, because friction in the control surface

rigging may cause a very slight control deflection. In a moderately banked turn, if the aileron

and rudder pressures are released, the aircraft will tend to stay at the established angle of bank.

In a steep angle of bank turn, the aircraft will tend to steepen its bank. The actual amount of

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

Figure 4-6 illustrates the explanation of the airplane's overbanking tendency during a steep turn;

as the radius of the turn becomes smaller, a significant difference develops between the speed of

the inside wing and the speed of the outside wing. The wing on the outside of the turn travels a

longer circuit than the inside wing, yet both complete their respective circuits in the same length

of time. Therefore, the outside wing must travel faster than the inside wing and as a result it

develops more lift. This creates a slight differential between the lift of the inside and outside

wings and tends to further increase the bank.

FUNDAMENTAL FLIGHT CONCEPTS

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