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.

Overview

1. The Axes of Rotation

2. Flaps

3. Slats

4. Spoilers

5. Drag Devices

6. Controlled Flight

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.

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.

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.

The Axes of Rotation

• Longitudinal Axis• When an aileron is not perfectly aligned with

the total wing, it changes the wing’s 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.

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 airfoil’s lift.

• The “up” aileron’s 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.

The Axes of Rotation

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 airplane’s 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.

The Axes of Rotation

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 airplane’s rudder is responsible for the movement about this axis.

The Axes of Rotation

Flaps

• The flaps are attached to the trailing edge of the wing. In cruising flight, the flaps simply continue the streamline shape of the wing’s airfoil.

• When flaps are lowered either partially or fully, lift and drag are increased.

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.

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.

Flaps and Slats

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.

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.

Spoilers

• A favorable feature about spoilers is that they can be deployed or retracted quickly.

• The use of flaps lowers the stalling speed.

Spoilers

Drag Devices

• These devices may be located at the trailing edges of the wings, or they may protrude from the aircraft’s 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 airfoil’s lift.

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.

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 airplane’s pitch attitude is reduced and the airplane accelerates to cruising speed.

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.

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.

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.

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.

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.

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.

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.

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.

Controlled Flight

• Landing• The pilot’s 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.

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.

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.

Summary

1. The Axes of Rotation

2. Flaps

3. Slats

4. Spoilers

5. Drag Devices

6. Controlled Flight