Turns

Turn

The  turn is the basic manoeuvre used to change heading of an aircraft.

Objectives of the lesson

To learn:
  • How to Turn to selected headings
  • How to make gentle, medium, climbing and descending turn. 

Why ?

  • It`s necessary maneuvers at every flight; navigate, turn in circuit etc….
Link:
  • Attitudes and movements, climbing and descending lessons.

Review questions

  • What is angle of attack ?
  • What happens to load factor as the angle of bank is increased ?
  • Can you control your rate of descent with pitch attitude ?
  • What is the primary reason for making trim adjustements ?
  • Which type of climb speed results in the greatest gain in altitude in the shortest distance ?
Why the airplane turn?

The horizontal component of lift causes airplanes to turn.

This horizontal component is attained thru the coordinated use of :

  • Ailerons
  • Rudder
  • Elevator

Important:

*The rudder causes yaw but does not cause the airplane to turn.

Load factor

Load factors refers to the additional weight carried by the wings due to the airplane’s weight + the centrifugal force.

The amount of excess load that can be imposed on an airplane’s wings varies directly with the airplane’s speed and the excess lift available.

  • At low speeds, very little excess lift is available, so very little excess load can be imposed.
  • At high speeds, the wing’s lifting capacity is so great that the load factor can quickly exceed safety limits.

An increased load factor will result in airplane stalling at a higher airspeed.

As bank angle increased, the load factor increases. The wings have to carry not only the airplane’s weight but the centrifugal force as well.

Don’t forget: centrifugal force is acting in the opposite direction of the turn.

Proper use of rudder in coordinated turn

Coordinated flight is flight without skid or slip, the ball stay centered.

Push rudder on the side of the ball.

  • First picture push the left rudder.
  • Third picture push the right rudder.

Turns: Radius and rate

At constant airspeed, the greater the angle of bank the:
  • Greater the rate of turn
  • Smaller the radius of turn
  • Higher the stalling speed
  • Greater the load factor

The higher the airspeed at a constant angle of bank the:

  • Lower the rate of turn
  • Larger the radius of turn

To achieve a turn at the smallest radius and greatest rate for a given angle of bank, fly at the lowest possible airspeed for that angle of bank.

But don’t forget !!!  The stalling speed increases as angle of bank increases.

Types of turns

Level turn
  • Gentle turns: Involving angles of bank up to 15 degrees.
  • Medium turns: Involving angles of bank from 15 degrees to 30 degrees.
  • Steep turns: Involving angles over 30 degrees.
Climbing turns:
  • Which are normally gentle
 Descending turns:
  • Which may be gentle, medium or steep.

Turn entry

  • Be sure that the aircraft is in straight-and-level flight.
  • Look around for other aircraft.
  • Roll the aircraft gently to the desired bank attitude with aileron control.
  • Maintain this attitude.
  • At the same time, use appropriate rudder pressure to control any tendency for the aircraft to yaw adversely.
  • Use elevator to maintain the aircraft in the correct pitch attitude in relation to the horizon.
  • Maintain look out.

  • Position of the dashboard in relation to the horizon during the turn.
  • The angle between the dashboard and the horizon line is greater as the angle of bank is steeper.

As angle of bank is increased beyond a gentle turn, the pitch attitude must be changed (by backward pressure on the control column) to increase lift, this is to compensate for the added load factor imposed by centrifugal forces as the turn steepens.

  • When entering a turn, aileron and rudder are applied simultaneously and in the same direction. This is what it means when we refer to « flying coordinated« .
  • Aileron establishes the degree of bank, and rudder keeps the nose pointed in the direction of turn. If the ball is centered during this process, we say that the controls are properly coordinated.

During the turn

  • The nose will move steadily around the horizon, neither rising nor falling.
  • The airspeed will be constant.
  • The turn indicator will show a constant rate of turn.
  • The ball will be centered in its glass tube.
  • The altimeter will be steady on the selected altitude.

Turn: posture

  • Sit comfortably upright.
  • Continually changing sitting position affects visual references and may cause handling of the controls to become tense and erratic.

Turn recovery

  • Look around.
  • Start to roll the wings level prior to the specified landmark with aileron control.
  • At the same time, use appropriate rudder pressure to control adverse yaw.
  • Keep wing level.
  • Maintain correct pitch attitude with elevator control.
  • Keep straight.
  • Trim

Rule of Thumb:

Start roll out from a turn when heading to go = bank angle/2

Climbing Turn

  • Climbing turns are executed like level turns except that, instead of maintaining a constant altitude, a constant climb is maintained.
  • Additional power is required to achieve the desired increase in altitude.
  • Your rate of climb will be less for climbing turn than normal climbs.
  • Generally, the climbing turn is performed using shallow bank angles, because steep bank angles divert more of the vertical component of lift, which cause a reduction in rate of climb.

Descending turn

  • Descending turns are executed like level turns except that, instead of maintaining a constant altitude, a constant descent is maintained.
  • The rate of descent will be higher in a descending turn than in a normal descent with a comparable power setting because the vertical lift component is less when the airplane is in a banked attitude. You can compensate for this with a slight addition of power over what is used in a straight descent.

Use power to control the rate of descent:

  • Make the intial power setting for the desired rate of descent and allow pitch attitude and the rate of descent to stabilize.
  • If you desire a higher rate of descent, reduce power.
  • If you desire a lower rate of descent add power.

Review: questions

  • How are turns classified ?
  • Describe the different types of turns?
  • As we roll into, or recover from a turn, rudder control is used. What is the reason for this ?
  • You are in a climbing turn to the right, using 20° angle of bank and have been directed to rollout on a heading of 075°. On what heading should you begin to rollout ?