Time for Flight 1.4 – Principles of Flight

An aircraft in flight is not magic, so you must understand the core of the underlying principles to be an aircraft pilot.

First posted on

Last updated on

Contributed By

Image by Todd MacDonald from Pixabay

Time for Flight -Home Series Part 1 Step 4

What keeps an Aircraft in Air?

The movements of air provided by the aircraft design create the forces to keep an aircraft in air. The design of lifting surfaces (mainly wings), propellers and or jet engine turbines, and compressors are the main components that keep an aircraft in air. Air in the atmosphere represents the theatre of operations for an aircraft in flight.

It is essential, therefore, to understand the atmosphere and the air it contains for learning to be an aircraft pilot.

Air in the atmosphere is affected by temperature, pressure and humidity. The state of the air at each instant of an aircraft in air affects its behaviour and performance. The effects of the weather on an aircraft in air makes safe flight a challenge. It is a primary concern for all aircraft pilots.

Flying in your free flying simulator does not create the sensations caused by the conditions above. It is therefore easy to dismiss and ignore the importance of this element during in flight training when using the free flying simulator. Thorough appreciation and understanding of the instruments in the aircraft simulator is therefore mandatory to interpret aircraft behaviour during flight training .

The Pilot Training System Principles of Flight Video

This 10-minute video packs the essential information required to give you a sound understanding of what keeps an aircraft in air. Watch the above once to get an idea of what it contains. Viewing the above 10-minute video will give you a better understanding while studying chapter 4 of the FAA Pilot’s Hand Book of Aeronautical Knowledge (PHAK).

What Are The Basic Properties of Air?

Air as matter possesses mass, exerts pressure, occupies space and has weight. The combination of temperature, density and pressure provides the conditions to manoeuvre and keep an aircraft in air safely and within the limits of the aircraft design.

Chapter 4 of the PHAK clearly explains the properties we must know to understand the Principles of Flight. The following video helps illustrate these properties and makes the subject easier to understand.

Air in the atmosphere exerts pressure. It is compressible in a closed container but considered incompressible when moving in a steady flow in the atmosphere at below the speed of sound. There are different types of pressure for air in the atmosphere, demonstrated in this video.

Air density affects aircraft performance directly. The video below is a simple explanation of the effects of temperature, pressure and humidity.

The amount of water vapour in the air is known as humidity.

Water vapour is water in a gaseous state and directly affects the density of the surrounding air. So is dry air heavier or lighter than moist air?

The ICAO standard Atmosphere (many also refer to it as the International Standard Atmosphere) is a concept for referencing a standard ideal atmospheric condition at sea level. Fixed values for air pressure, density and temperature at sea level are assigned and accepted by the aviation community.

Its use and function at this stage may be difficult to appreciate, but will become easier to understand when the principles of aircraft instruments and performance are studied. Making complete sense of these subjects will require a thorough understanding of the ICAO Standard Atmosphere (ISA).

Here is a video to help you understand the ISA.

These laws have been accepted, but may have been oversimplified. Appreciating the underlying principles of these laws is the key to understanding the Principles of Flight. The learning process will be more meaningful in the progression of learning to be a pilot. A good grasp of these principles will make aerodynamics, control of flight and other related subjects easier to understand.

The video below explains the concept and evolution of the three laws of motion and is enlightening.

The Magnus Effect occurs when rotating a cylinder in an air stream. It contends that the air which tends to cling to one side of the rotating surface causes a downwash. It creates opposite Magnus force on the cylinder.

With an airfoil (the cross-section of a typical aircraft wing), the air which sticks to the top curved surface (called the Coandă effect) produces a downwash similar to the Magnus effect. In the interest of keeping continuity of this part 4 lesson, go straight to 1 min 49 seconds of the video below and watch until it reaches 2 min 49 seconds. It directly answers the question of how wings primarily create lift!

It is the most popular concept accepted and used to explain lift creation from an aircraft’s wing. Its relevance on how it causes lift appears to have been debated and argued more recently. But all agree that the theory is relevant for creating lift forces.

Watch and appreciate the explanation of Bernoulli’s principle.

An airfoil is the shape of the cross-section of the lifting surface of an aircraft or helicopter, propeller, rotors, wings and any other components of an aircraft designed to create lift or thrust from the air it moves in.

The variations of an airfoil shape are selected for different flight roles when designing an aircraft. They provide different results for aircraft performance to suit the intended purpose of the aircraft design. All airfoil designs have the same component names used to describe their shape.

The variations of an airfoil shape are selected for different flight roles when designing an aircraft. They provide different results for aircraft performance to suit the intended purpose of the aircraft design. All airfoil designs have the same component names used to describe their shape. View the video again, but this time only from 6 min 14 sec to 7 min 13 sec, to understand the components of an aerofoil shape.

Airfoil shapes and designs are continually evolving due to many research activities. As mentioned, each shows different characteristics when moved through the air. The video below shows some popular airfoil designs from the above video again to see some examples of airfoil designs (from 7:11 to 7:58).

The material in the video seems to be an excellent summary of the Theory of Flight derived from chapter 4 of the PHAK.

Watch all the first video at the top of this article again after reviewing all the other additional videos above. It should reinforce your understanding of the Principles of Flight. You must strive to improve and expand your knowledge base from these and other resources on the internet, many of which are free.

Again, as described in Part 1.1 of this series, do the quiz related to the topic to see how far you have understood the subject. The better you score. Strengthening your knowledge will make teaching yourself to fly for free more meaningful.

Self studying at your own pace while repeating these lessons as often as necessary is the big plus of the free home flight training system. It truly allows anyone to start ground training, albeit with the caveats mentioned earlier.

More free ground training resources with greater detail on specific subjects can also be found. You will quickly learn where to find them as you progress with the free Pilot Training System.

Image by David Mark from Pixabay


We welcome your insightful comments, views, and arguments. Please send your email to info@esbaviation.com.

Mohd Raffick Bin Mohd Nor

An extremely passionate veteran aviator and Aircraft Engineer. He has been involved with youth development in aviation for more than 50 years. Currently the principal contributor and founder of the The Budding Aviator’s Hub

Latest Posts

1 2

Check out our other posts