405: Theory of Flight

What is defined as any machine capable of deriving support in the atmosphere from reactions of air?

Aircraft

What is a power-driven, heavier-than-air aircraft that derives lift from aerodynamic reactions?

Airplane

What does the term airframe refer to?

The complete structure of an airplane, excluding instruments and engine.

Define camber as it pertains to aircraft wings.

The curvature of the upper and lower surfaces of a wing.

What is the imaginary straight line joining the leading and trailing edges of a wing called?

Chord

What does 'span' refer to in the context of wings?

The maximum distance from tip to tip of an airfoil, wing, or stabilizer.

What is the Mean Aerodynamic Chord (MAC)?

The average chord of the wing.

How is wing area calculated?

Wing area = length (span) x width (chord).

What does the aspect ratio refer to in wing design?

The relationship between the length and width of the wing.

What are the two definitions of 'angle of incidence'?

The angle the wing is inclined to the longitudinal axis of the plane.

What is the angle of attack?

The angle where the airfoil meets the relative airflow.

How does the angle of attack affect lift?

Increasing the angle of attack increases the pressure differential between the upper and lower surfaces of the wing, creating more lift until the stall stage is reached.

What are the three axes around which aircraft movement occurs?

Longitudinal axis, lateral axis, and vertical/normal axis.

What are the movements of an aircraft around its three axes called?

Roll (longitudinal), pitch (lateral), and yaw (vertical).

What type of control surface controls movement around the longitudinal axis?

Ailerons.

Where are elevators located, and what do they control?

Located on the horizontal stabilizer, they control movement around the lateral axis.

What does the rudder control in an airplane?

Movement around the vertical axis (yaw).

State Newton’s First Law of motion.

A body persists in its state of rest or uniform motion unless acted upon by an external unbalanced force.

What is the equation for Newton’s Second Law?

Force = mass x acceleration.

Explain Newton's Third Law of motion.

For every action, there is an equal and opposite reaction.

What defines lift in aviation?

The upward force that sustains the aircraft in flight.

What is weight in the context of aircraft?

The downward force on an aircraft due to gravity.

Define drag in the context of an airplane's motion.

The resistance of the aircraft moving forward, opposing thrust.

Describe thrust in aviation.

The force exerted by the engine to push air backwards, causing a forward reaction.

What is static equilibrium in aviation?

When all forces acting on an aircraft are balanced, resulting in steady motion.

What is Bernoulli’s Principle?

As the speed of a fluid increases, its pressure decreases.

How does airflow behave over the upper and lower surfaces of a wing?

Air travels faster over the upper surface, creating lower pressure, and slower beneath, creating higher pressure.

What is meant by the center of pressure?

The point where all distributed pressures on a wing act equivalent to a single force.

What happens to the center of pressure as angle of attack increases?

It moves forwards up to the stall point and then back beyond it.

What are the two types of drag experienced by an aircraft?

Parasite drag and induced drag.

Define parasite drag.

Drag caused by all parts of an aircraft that do not contribute to lift.

What causes induced drag?

Created by parts of the aircraft that produce lift.

Explain what form drag is.

Drag created by the shape of the body as it resists motion through air.

What is skin friction in aerodynamics?

The resistance of air flowing over a surface due to its tendency to adhere to that surface.

Define streamlining in aviation design.

Designing the aircraft body to minimize drag as it moves through air.

What is the best glide speed?

The airspeed that allows the aircraft to glide the furthest distance with the least altitude lost.

What is the significance of 'best rate of climb'?

The rate of climb that gains the most altitude in the least amount of time.

What does the term 'minimum sink speed' mean?

The airspeed used to remain aloft the longest time.

What is the transition point in laminar flow?

The point where the boundary layer becomes turbulent as air flows over the wing.

Define stability in aviation.

The tendency of an aircraft in flight to maintain its altitude and heading without pilot intervention.

What is the difference between static stability and dynamic stability?

Static stability refers to the initial tendency to return to the original position, while dynamic stability refers to the overall tendency to return after oscillations.

What is inherently stable in aviation design?

An aircraft designed to be stable within the proper center of gravity limits.

What is a stall in aviation?

When a wing cannot produce enough lift to counteract the weight, causing the aircraft to fall due to gravity.

What symptoms indicate an impending stall?

Nose high attitude, low airspeed, lack of wind noise, and buffeting.

How does the center of gravity affect stall speed?

Forward CoG increases stall speed; backward CoG can cause instability.

What is a spin in aviation terms?

A stalled condition from which the aircraft starts to auto-rotate.

How can a spin be recovered?

By applying full opposite rudder and then neutralizing the controls.

What distinguishes a spiral dive from a spin?

A spiral dive involves a steep descending turn without stalling, whereas a spin is a stalled condition with auto-rotation.

What is an incipient spin?

The portion of the spin between stalling and the start of rotation.

What do spoilers do on an aircraft?

Disrupt laminar airflow over the wing to decrease lift.

What is the function of trim tabs?

To help maintain the aircraft's attitude by alleviating control pressure.

Why are flaps used on an aircraft?

To allow the aircraft to fly at slower speeds and lower stall speeds.

How does adverse yaw affect aircraft during a turn?

The aircraft's nose yaws opposite the direction of the turn due to induced drag.

What is a side slip maneuver used for?

To maintain heading in crosswinds or lose height while turning.

How does the angle of bank in a turn affect lift?

It increases the lift required to sustain flight as the angle of bank increases.

Define altitude loss in a forward slip.

A condition where the longitudinal axis is not aligned with the flight path to lose excess height.

What occurs in a spinning turn?

A deliberate uncoordinated turn that can be used to descend while turning.

What is the effect of lowering flaps on an aircraft?

It increases the camber of the wing and decreases stall speed.

How can controlled slips be utilized in aviation?

To lose altitude or correct lateral drift during the final approach.

What is the recovery procedure for a spin?

Apply full opposite rudder, stabilize the control column, and pull out of the dive.

What adverse condition can result from improper weight distribution?

It can cause rolling motion in the aircraft.

How do heavy rain and icing conditions affect an aircraft?

They disrupt airflow and increase stall speed.

What is the significance of having a keel effect in aircraft design?

It helps stabilize the aircraft in yaw by acting like a pendulum.

How are adverse yaw and coordinated flight connected?

Adverse yaw must be countered by coordinated rudder use to maintain effective turns.

What is a flat spin, and why is it dangerous?

A spin where the aircraft has a level pitch and roll attitude, leading to difficult recovery.

How does the climb angle relate to the aircraft's performance?

The best angle of climb gains maximum altitude over a given distance.

What is the purpose of a laminar flow airfoil?

It promotes smooth airflow and extends laminar flow, which enhances lift and reduces drag.

What can cause a decrease in lift at low speeds?

Accumulation of snow, ice, or other debris that disrupts airflow.

In what situation might a stall happen during maneuvering?

When the angle of bank increases without sufficient lift being maintained.

Describe the recovery technique from a spiral dive.

Coordinated roll to level the aircraft followed by pulling out of the dive.

What challenges might pilots face during recovery from a stall?

Increased control sensitivity and reduced effectiveness of control surfaces at low speed.

What is indicated when the airspeed drops during a turn?

An increased risk of stalling due to increased load factor.

What must pilots do to manage adverse yaw?

Use rudder in coordination with ailerons during turns.

How can designing aircraft with high aspect ratio wings help?

They generate more lift and less drag.

What is effect of turbulence on stall recovery?

Turbulence can increase the angle of attack leading to a potential stall.

What does the angle of attack increase result in?

An increase in both lift and drag until the stall point.

Explain how weight affects stall speed.

As weight increases, a higher angle of attack is needed to produce lift, raising stall speed.

What is the role of winglets in modern aircraft?

To reduce induced drag by minimizing wingtip vortices.

During a forward slip, what happens to the glider's longitudinal axis?

It becomes misaligned with the flight path.

How can pilots use flaps for landing?

To reduce stall speed and allow for a slower landing approach.

Explain the relationship between lift, weight, thrust, and drag in steady flight.

In steady flight, lift equals weight, and thrust equals drag.

What happens during an incipient spin?

The aircraft is stalled and begins to rotate, but full rotation has not yet begun.

What should a pilot do in response to signs of a pending stall?

Reduce the angle of attack and gain airspeed.

What is the function of dive brakes during flight?

To increase drag and reduce airspeed while descending.

How does airspeed affect lift generation?

Higher airspeed generally increases lift until stalling occurs.

What feature of aircraft design helps to counteract adverse yaw?

Coordinated use of rudder during turns.

What is a critical angle of attack?

The maximum angle of attack at which an airfoil can produce lift before stalling.

How does maintaining proper control surface deflection help with wing performance?

It maximizes lift and minimizes drag during different flight conditions.

What can pilots do to minimize chances of entering a spin?

Avoid abrupt changes in control inputs and ensure proper coordination.

Why is it important to monitor the center of gravity in an aircraft?

Improper balance can lead to unstable flight characteristics.

What happens if the center of pressure moves too far backward on a wing?

It can lead to instability and difficulty managing the stall.

What might cause a decrease in the aircraft's lift coefficient?

Damaged or dirty wing surfaces affecting airflow.

What should be done with elevators when increasing airspeed in flight?

Trim the elevator to hold a desired climb or descent attitude.

Why is the understanding of lift and drag critical for pilots?

To manage aircraft performance, safety, and efficiency during flight.

What primary factor should be evaluated in preventing stalls?

Maintaining control of angle of attack.

How do changes in atmospheric pressure affect aircraft performance?

Lower pressure can decrease lift generation.

In what situations would flaps be beneficial during takeoff?

To achieve a better angle of climb at reduced speed.

What does a high angle of attack increase during flight?

The potential for stalling.

What role does the boundary layer play in lift generation?

It is critical for maintaining smooth airflow over the wing to maximize lift.

What is the importance of retractable landing gear related to drag?

It reduces parasite drag during flight.