Aerodynamics Quiz on Flight Forces

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Questions and Answers

What are the four fundamental forces acting on an aircraft during flight?

Lift, Weight, Torque, Friction

Thrust, Gravity, Drag, Lateral Forces

Lift, Weight, Drag, Thrust (correct)

Lift, Load, Thrust, Drag

How does the center of gravity impact flight performance and stability?

An aft center of gravity improves lift.

A forward center of gravity decreases stability.

It has no effect on performance or stability.

A forward center of gravity enhances stability. (correct)

What is the term for the angle at which an aircraft maintains a glide?

Climb Angle

Approach Angle

Descent Angle

Glide Angle (correct)

What is the effect of drag on the glide ratio of an aircraft?

Drag decreases the glide ratio as airspeed increases. Signup and view all the answers

Which of the following factors contributes to an imbalanced center of gravity?

Unequal fuel distribution Signup and view all the answers

What is the glide ratio?

The ratio of horizontal distance traveled to vertical distance lost during a glide Signup and view all the answers

What effect does stall speed have on the center of gravity?

Stall speed increases with a rear center of gravity. Signup and view all the answers

Which factors specifically impact the still air sink rate of a glider?

Air density, weight, and wing design Signup and view all the answers

What determines the minimum sink speed for a glider?

The point on the glide polar with the lowest sink rate Signup and view all the answers

How can the best glide speed be identified from a glide polar graph?

By drawing a line from the origin that touches the curve at one point Signup and view all the answers

What effect does adding water ballast to a glider have?

It increases the minimum sink rate but maintains the best glide ratio Signup and view all the answers

What does a higher lift-to-drag (L/D) ratio indicate about the glide angle?

The glide angle becomes shallower Signup and view all the answers

In still air, at what speed should a glider be flown to minimize height loss during a flight?

At the best glide speed Signup and view all the answers

What effect does increasing the weight of a glider have on its performance in thermals?

Makes it harder to climb effectively in thermals Signup and view all the answers

What is another term for the best glide speed?

Best lift/drag (L/D) speed Signup and view all the answers

Which statement is true regarding the glide ratio of a CP-1 glider?

The maximum glide ratio is 13.6 Signup and view all the answers

What is the significance of the ratio (L/D)max in a power-off glide?

It helps calculate the minimum glide angle and maximum range. Signup and view all the answers

In a balanced turn, what is true about the lift vector?

It is inclined at an angle to the vertical. Signup and view all the answers

What happens to the altitude during a level coordinated turn?

Altitude remains constant. Signup and view all the answers

Which statement regarding the load factor is correct?

It is commonly expressed in terms of 'g's'. Signup and view all the answers

Which factor affects the turning radius of an aircraft?

The speed of the aircraft. Signup and view all the answers

What occurs when the lift in a level turn does not equal the weight of the aircraft?

The aircraft will descend. Signup and view all the answers

In the context of turning flight, what does radial acceleration refer to?

The acceleration directed towards the center of the turn. Signup and view all the answers

What defines a coordinated turn?

Proper balance between ailerons and rudder. Signup and view all the answers

What does the term 'Load Factor' refer to in the context of flight?

The ratio of lift to weight during different maneuvers Signup and view all the answers

Which factor primarily influences the stall speed of an aircraft?

Wing loading Signup and view all the answers

In a V-n diagram, the maneuver point is characterized by which two conditions?

Minimum turn radius and maximum turn rate Signup and view all the answers

What is the main limiting factor for high-speed flight as shown in the V-n diagram?

Structural design of the airplane Signup and view all the answers

What is indicated by the term 'Corner Velocity' in flight dynamics?

The speed at which the maneuver point is reached Signup and view all the answers

What does the 'g' limit refer to in aviation?

The maximum load factor the aircraft can withstand Signup and view all the answers

During a turn, as the angle of bank increases, what happens to the load factor?

It increases significantly Signup and view all the answers

How can an aircraft survive high G forces during maneuvers?

By using specialized equipment Signup and view all the answers

Study Notes

Theory of Flight

The four forces acting on an airplane are thrust, lift, weight, and drag.
Thrust is the forward force propelling the aircraft.
Lift is the upward force opposing weight, created by airflow over and under the wings.
Weight is the downward force due to gravity.
Drag is the backward force opposing thrust, reducing speed.

Introduction

Students will be able to describe the relationship between lift, weight, thrust, and drag; glide ratio; steady state flight and performance; theory of the turn; load factor and its influence on stalling; flight envelope and structural limitations; and methods of lift augmentation.

Four Forces of Flight

Lift is the upward force created by airflow over and under the wings.
Weight is the force pulling the aircraft downwards due to gravity.
Thrust is the forward force propelling the aircraft through the air.
Drag is the backward force that opposes thrust.

Vectors

Arrows showing forces acting on an airplane are called vectors.
The length of the arrow indicates the magnitude of the force.
The direction of the arrow indicates the direction of the force.
Multiple forces acting simultaneously combine to create a resultant force.

Lift

Lift is the key aerodynamic force that opposes weight.
Air flowing over and under the wings creates a pressure differential.
This difference in pressure generates lift.

Weight

Weight is a force caused by gravity acting on the mass of the aircraft.
Center of Gravity (CG) is the point where the entire weight of the aircraft is considered concentrated.
CG has a definite relationship with lift.

Centre of Gravity

CG is the point within an aircraft where the weight acts.
It is determined by the general design of the aircraft.
The designer determines how far the center of pressure will travel.
CG is placed in front of the center of pressure for correct flight speed.
- This provides restoring moment for flight equilibrium.

Adverse Forward Center of Gravity

When too much weight is towards the front of the aircraft, the CG is shifted forward.
Possible flight conditions include: increased tendency to dive, increased difficulty in raising the nose during landing, increased oscillation tendency, increased danger during flap operation, development of dangerous spin characteristics.

Adverse Rear Center of Gravity

When too much weight is toward the tail of the aircraft, the CG is shifted aft.
Possible flight conditions include: decreased flying speed, decreased range, increased danger of stall, dangerous spin characteristics, poor stability, and extreme shifts in CG, leading to an accident.

Effect of Stall Speed on Centre of Gravity

Airspeed and sink rate must both be in the same units.
Minimum sink speed is the airspeed at which the glider loses altitude at the lowest rate.

Aircraft Glide Ratio

Glide ratio is the number of horizontal feet a glider travels in still air for every vertical foot it loses.
This ratio varies with airspeed, as drag varies with airspeed.
A glide polar is a graph for this relationship, showing a minimum sink rate at a particular airspeed.

Glider Fly

Gliding flight occurs when thrust is removed from the four forces.
Lift, drag, and weight must be in equilibrium for a steady glide.
The angle of attack (AofA) is crucial for maximum lift/drag ratio and a steady glide.

Equations of Motion for Power-Off Glide

These equations describe the relationship between drag, lift, and weight during a glide, using variables (W-Weight, D-Drag, L - Lift, θ - glide angle).

Aircraft Turn

Inertia must be overcome for a turn.
Banking the aircraft tilts the lift direction, generating a horizontal turning component.
This horizontal component (centripetal force) and lift components are crucial for a turn.
Maintaining constant altitude requires balanced lift and weight during a level turn.

Sideslip

Sideslip occurs when the side wind is not coming from ahead of the aircraft.
If the bank is too great, a sideways force due to gravity will cause a skid.

Skidding

Skidding is caused by an insufficient bank angle or when a pilot does not correct for centrifugal force.
The wind will feel like it is coming from the outside of the turning plane.

Sideway Landing

Sideway landing is typical for crosswind conditions.

Cross Wind Landing

This is typical for when the wind is landing at an angle.

Balanced Turn

The pilot does not feel any sideways forces during a balanced turn.

Turning Flight and The V-n Diagram

A table shows that with no turn, no change in altitude happens, but with a turn there is either an increase or a decrease in altitude.

Level Turn (Coordinated Turn)

The lift is inclined at a bank angle ($ \phi $) to the vertical.
The vertical component of the lift exactly balances the weight. (L Cos $ \phi $) = W
Resultant force (F,)= √ L2 – W2 or F, = L sin $ \phi $

Load Factor

The load factor is the ratio between lift and weight(L/W).
Aircraft have load factor limits (5g, for example) for which structural damage may occur.

Load Factor During a Turn

Lift increases significantly during turns.
Lift bracing (struts, spars) is required to handle increased loads during turns.

Load Factor Angle of Bank

The stalling speed is calculated mathematically using the formula W/L = cos e, and L=W/cos e.
The factors are lift (L), weight (W), and angle of bank (e).
Stall and maneuvering speed are calculated using these.
Different values of the bank angle (e.g., 60, 70.5, 75.5, 80.25 degrees) for a given stalling speed can provide values of turning lift.

Wing Loading

Wing loading is the aircraft's weight divided by the wing area.
Weight compared to wing area governs the minimum speed.
Lower Wing loading = lower minimum speed
Higher Wing loading = higher minimum speed

Wing Loading Stalling Speed

Lower wing loading = lower stalling speed
Higher wing loading = higher stalling speed
Adding weight to the aircraft increases wing loading, minimum speed, and stalling speed.

"g" Limit

"g" limit is an aircraft's ability to withstand structural stress during turns
High g-forces lead to structural damage

How to survive high G force?

High G suits might be needed.

"g" Limit from V-n diagram

The V-n diagram displays the relationship between airspeed and load factor for various flight conditions.

V-n diagram (Low Speed)

This diagram shows how stall limits and structural limits affect the maximum load factor, along with speed.

V-n diagram (High Speed)

The maximum load factor is limited by the aircraft's structural designs.

Maneuver point

The maneuver point is a point on the curve where the load factor and speed are highest and where the maximum aerodynamic lift and load factor are realized, before stall or structural failure.

Corner velocity (v*)

The corner velocity is the speed at which the aircraft achieves its maximum turn rate.

V-n diagram (Low speed) and V-n diagram (High speed)

Stall limits and structural limits affect maximum load factors and speeds.

Additional notes:

Figures and diagrams will greatly aid understanding.

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Description

Test your knowledge on the fundamental forces acting on an aircraft during flight, including the impact of center of gravity and drag on performance and stability. This quiz covers various factors affecting flight characteristics such as glide ratio and stall speed.