Aircraft Motion and Control

1
Aircraft Motion and Control

• Know aircraft motion and how it is controlled.
• 1. Identify the axes of rotation.
• 2. Identify the effects of flaps on flight.
• 3. Identify the effect of slats on flight.
• 4. Identify the effects of spoilers on flight.
• 5. Identify the effects of drag on flight.
• 6. Describe the elements of controlled flight.

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Overview

• 1. The Axes of Rotation
• 2. Flaps
• 3. Slats
• 4. Spoilers
• 5. Drag Devices
• 6. Controlled Flight

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The Axes of Rotation

• The fuselage of the conventional airplane is the
  basic structure to which all the other parts are
  attached. The wings, which are the primary
  source of lift, have ailerons attached to them.
  The tail, or empennage, consists of the
  horizontal stabilizer, with attached elevators
  and the vertical stabilizer, with attached rudder.

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The Axes of Rotation

• Longitudinal Axis
• Running from the tip of the nose to the tip of
  the tail. This axis can be thought of as a
  skewer which turns either right or left and
  causes everything attached to it to turn.

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The Axes of Rotation

• Longitudinal Axis
• The cause of movement or roll about this axis (or
  roll axis) is the action of the ailerons.
  Ailerons are attached to the wing and to the
  control column in a manner that ensures one
  aileron will deflect downward when the other is
  deflected upward.

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The Axes of Rotation

• Longitudinal Axis
• When an aileron is not perfectly aligned with the
  total wing, it changes the wings lift
  characteristics.
• To make a wing move upward, the aileron on that
  wing must move downward.
• The pilot can cause a wing to lift very slightly,
  or by very positive movement on the controls, the
  wing can be made to rise very quickly.

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The Axes of Rotation

• Longitudinal Axis
• While the one wing is moving upward the other
  wing is moving downward due to the deflection of
  its aileron. The reason again is a change in the
  amount of the wing airfoils lift.
• The up ailerons deflection is greater than
  that of the down aileron. The up aileron
  must be deflected to a greater degree in order
  for it to affect the airflow and change the lift
  characteristic of the wing.

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The Axes of Rotation
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The Axes of Rotation

• Lateral Axis
• An imaginary rod, running from one wing tip
  through the fuselage and exiting the other wing
  tip, forms an airplanes lateral axis.
• Another name for the lateral axis is the pitch
  axis.
• The elevator can be deflected up or down as the
  pilot moves the control column backward or
  forward.

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The Axes of Rotation
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The Axes of Rotation

• Vertical Axis
• An imaginary rod or axis which passes through the
  meeting point of the longitudinal and lateral
  axes. It is also referred to as the yaw axis.
• The airplane turns about this axis in a
  side-to-side direction.
• The airplanes rudder is responsible for the
  movement about this axis.

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The Axes of Rotation
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Flaps

• The flaps are attached to the trailing edge of
  the wing. In cruising flight, the flaps simply
  continue the streamline shape of the wings
  airfoil.
• When flaps are lowered either partially or fully,
  lift and drag are increased.

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Flaps

• Flaps increase the camber of the wing airfoil for
  the portion of the wing that it is attached.
• This causes the air to speed up over the wing
  section where the most lift is created.
• On the underside of the wing, dynamic lift is
  increased.
• When landing, flaps permit the steep descent that
  may be necessary to land on a short runway.
• Using flaps when taking off helps the airplane
  get off the ground in a shorter distance.

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Flaps

• In addition to the simple hinge flap there are
  much more complicated ones.
• When an extended flap leaves a space between the
  wing and flap, it is known as a slotted flap.
• This happens because the high-speed relative wind
  going through the slot adds energy to the upper
  wing airflow.

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Flaps and Slats
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Slats

• Slats are protrusions from the leading edge of a
  wing.
• The secret of the slat is the slot it produces.
• In normal flight the relative wind struck the
  leading edge of the slat, passed over the slot,
  and continued around the airfoil.
• Modern airplanes have retractable slats.

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Spoilers

• Spoilers work to destroy lift.
• Spoilers are found on various aircraft from the
  jet airliner to the sailplane.
• On the jet airliners, spoilers are hinged so that
  their aft portion is tilted upward into the
  smooth airflow.

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Spoilers

• A favorable feature about spoilers is that they
  can be deployed or retracted quickly.
• The use of flaps lowers the stalling speed.

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Spoilers
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Drag Devices

• These devices may be located at the trailing
  edges of the wings, or they may protrude from the
  aircrafts fuselage upon activation by the pilot.
• These devices may be called dive brakes, air
  brakes, dive flaps, or drag parachutes. Their
  purpose is to produce a significant amount of
  drag without affecting the airfoils lift.

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Controlled Flight

• Takeoff and Climb
• After taxiing to the runway, a pre-takeoff
  checklist is accomplished.
• As take off airspeed is approached, gentle back
  pressure on the control wheel raises the elevator
  which causes the nose to pitch upward.
• Once the nosewheel is off the runway, right
  rudder is applied to counteract the left-turning
  tendency, which is present under low airspeed,
  high-power flight conditions.

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Controlled Flight

• Takeoff and Climb
• As airspeed increases to the best rate-of-climb
  airspeed, back pressure on the control wheel is
  adjusted to maintain that airspeed until the
  first desired altitude is reached.
• Upon reaching cruising altitude, the airplanes
  pitch attitude is reduced and the airplane
  accelerates to cruising speed.

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Controlled Flight

• Basic Flight Maneuvers
• Basic flight maneuvers are started from straight
  and level flight.
• Power setting is maintained at 55 to 75 percent
  of available power.
• A series of slight adjustments or corrections in
  pitch, yaw, and roll are made to keep the wings
  level and heading and altitude constant.
• Basic flight maneuvers include climbs, descents,
  turns, and a combination of these.

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Controlled Flight

• Climbs are a combination of power and up
  elevator.
• Best angle-of-climb.
• The climb angle is steep and all available power
  is used.
• Used when the pilot must rise quickly after
  take-off to avoid objects at or near the end of a
  runway.
• Other than best-rate and best-angle climbs, most
  climbs are very gentle at low angles of attack.

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Controlled Flight

• Descent
• A combination of reducing power and adjusting to
  maintain the desired airspeed. Airspeed is
  maintained by varying pressure on the control
  wheel. This varies the angle of attack and
  airspeed.
• The rate of descent, measured in feet per minute,
  is controlled by applying or reducing power as
  needed.

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Controlled Flight

• Turns
• Turns are either gentle, medium, or steep, and
  they may be made when climbing, descending, or
  while not gaining or losing altitude.
• Causing the airplane to turn requires smooth
  coordination of aileron, rudder and elevator
  controls, pressure on the control wheel and
  rudder pedal should be applied simultaneously.

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Controlled Flight

• Turns
• The moment a wing begins to rise in a banked
  turn, it experiences more drag because of the
  lowered aileron and its higher angle of attack.
• Once the coordinated turn is established,
  ailerons and rudder usually are neutralized.

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Controlled Flight

• Turns
• In-flight turns are measured as the number of
  degrees of bank involved.
• At 60o of bank the airplane experiences twice the
  normal force of gravity (2Gs).
• At 80o of bank a force of almost six times that
  of normal gravity is felt.
• The average light airplane has a design limit of
  approximately 3.8Gs.
• In steep turns, those of 35o or more of bank,
  considerable back pressure on the control wheel
  is required to produce the needed amount of lift.
  

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Controlled Flight

• Landing
• A good landing begins with a good approach.
• Flaps are used to permit a lower approach speed
  and a steeper angle of descent.
• The airspeed and rate of descent are stabilized
  and the airplane is aligned with the runway
  centerline as the final approach is begun.

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Controlled Flight

• Landing
• When the airplane descends across the approach
  end (the threshold) of the runway, power is
  reduced.
• Continuing back pressure on the control wheel, as
  the airplane enters ground effects and gets
  closer and closer to the runway, further slows
  its forward speed and rate of descent.

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Controlled Flight

• Landing
• The pilots objective is to keep the airplane
  flying safely just a few inches above the runway
  until it loses flying speed.
• With the wheels of the main landing gear firmly
  on the runway, the pilot applies more back
  pressure on the control wheel.

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Controlled Flight

• Stalls
• At the critical angle of attack, air going over a
  wing will separate from the wing or burble,
  causing the wing to lose its lift (stall).
• This speed will vary with changes in wing
  configuration (flap position).
• Most airplanes give adequate warning as the
  stalling speed is approached.

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Controlled Flight

• Stalls
• Newer aircraft have stall warning horns and/or
  lights that activate 5 to 10 knots above the
  stalling speed.
• When the wing stalls, the nose of the airplane
  starts dropping, even though the control wheel
  may be in the full back position.

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Summary

• 1. The Axes of Rotation
• 2. Flaps
• 3. Slats
• 4. Spoilers
• 5. Drag Devices
• 6. Controlled Flight