"Fundamentals of Flying" deals with the basic aerodynamic processes that cause an aircraft to fly. Firstly, air as an element and the atmosphere are dealt with, as well as air resistance and how this changes. Aspects relating to flow, lift and drag are explained and how they behave in the various phases of flight. It also deals with the control of the aircraft around the three axes, as well as special flight conditions such as "stalls" or spins.
Air and resistance
This is about the basic principles of aerodynamics and their application in aircraft construction. It is important to realise that air is much more than "nothing" and that its properties are essential for flying. The composition of the atmosphere, consisting mainly of nitrogen, oxygen and other gases, influences the design of wings and engines. With increasing altitude, air pressure and density decrease exponentially. Aircraft mainly travel in the troposphere, where the temperature decreases with altitude.
The air resistance that occurs when a body moves through air is explained. Important factors influencing air resistance are the shape of the body, its size, air density and the speed of the body. Air resistance is described mathematically by a formula that includes the speed, the frontal area, the air density and the drag coefficient.
The drag coefficient is determined experimentally or in simulations and depends on the shape and flow direction of the body. An efficient flow minimises the air resistance.
The boundary layer, an area near the surface of a flowing body, has two forms: laminar and turbulent. Laminar flow occurs at lower speeds and has less resistance, while turbulent flow occurs at higher speeds and, despite higher resistance, offers advantages when flowing around curved surfaces.
The Bernoulli equation, a fundamental concept in aerodynamics, explains the relationship between velocity and pressure in a flow. An increase in speed leads to a decrease in static pressure. This principle is used in the design of wings to generate lift.
Buoyancy and flow
This theory area describes how different shapes and features of aerofoils influence the aerodynamics of aeroplanes. It is explained that almost any body can generate lift if it is subjected to a suitable flow, but aerofoil profiles are particularly efficient at generating lift. The importance of the angle of attack for the relationship between lift and drag and the effects of three-dimensional wing geometry on the flow and drag generated by lift are emphasised.
Various types of drag that occur in the flow around an aerofoil are explained, including profile drag (form drag and frictional drag), induced drag and interference drag. It is emphasised that the total drag of an aircraft results from the sum of these drag types.
Design features of aerofoils, such as airfoil shapes, wing shapes, wing tip pitch and aerodynamic aids (boundary layer fences, winglets, trailing edges and vortex generators) are discussed. These features are crucial for minimising drag and ensuring good flight characteristics when lift is high.
Overall, this section covers in detail how the shape and characteristics of airfoils affect aircraft performance and efficiency, and discusses various methods to minimise drag and optimise flight performance.
Furthermore, the forces acting on an aircraft during flight are explained in detail. In unaccelerated level flight, four main forces are in balance: lift force, weight force, thrust force and drag force. However, this balance can easily be disturbed by external influences or control movements, resulting in climbing, descending or turning flights.
To control the aircraft, the pilot must actively influence the force ratios, which is mainly achieved by changing the engine power, lift and cornering attitude. The aircraft's response to such changes depends on its design. It also describes how lift and weight, thrust and drag interact and what role the ground effect plays at low altitudes.
Special flight conditions such as climbing, descending and cornering are also discussed. In climbing flight, for example, the lift force must exceed the weight force, which can be achieved by increasing the speed or the angle of attack. In descent, on the other hand, the lift force is reduced. When cornering, centrifugal force also occurs, which must be balanced by a horizontal component of the lift force.
It also explains gliding flight, which is particularly relevant for gliders, and describes the glide polars, which show the rate of descent as a function of airspeed. This information is important in order to determine the optimum speed for the best glide, which is particularly important in the event of an engine failure.
The ground effect that occurs at low altitudes leads to increased lift and reduced induced drag, which must be taken into account when landing. Finally, various aircraft categories are presented based on the safe load multiple.
Control around the three axes
This theory chapter is about aircraft design and ensuring stability in normal operating conditions. The arrangement of the control surfaces such as wings, horizontal and vertical stabilisers plays an important role in stability, which is supported by features such as the dihedral of the wings. A distinction is made between static and dynamic stability. Static stability ensures that the aircraft returns to its original state of motion after a disturbance, while dynamic stability ensures that no unwanted further movements take place once the initial position has been reached.
The aircraft can perform movements in three spatial directions, which take place around the longitudinal, lateral and vertical axes. These movements are controlled by various control surfaces: the elevator for climb and descent (pitch), the aileron for roll and the rudder for yaw. The centre of gravity of the aircraft is decisive for the axes of rotation, and the pressure point at which the air forces act changes with the angle of attack.
The challenge is that the centre of pressure does not always coincide with the centre of gravity, which can cause unwanted rotations around the lateral axis. The tailplane therefore often generates downforce to create a balance and enable a stable flight condition. Furthermore, the effects of negative turning moment and push-roll moment when operating the ailerons and rudder are discussed and the need for coordinated control surface movement is emphasised.
This section also deals with the stability and control of aeroplanes, focuses on the importance of stability around the three main axes (longitudinal, lateral and vertical axis) and explains the principles of stability. Longitudinal stability (stability around the lateral axis) is particularly important as the centre of gravity can vary depending on the load. The tailplane plays a central role here. Lateral stability (stability around the longitudinal axis) is influenced by factors such as the V-shape of the wings. This shape helps to automatically return the aircraft to a horizontal wing position if a wing is lifted by a gust, for example. Directional stability (stability around the vertical axis) is largely achieved by the shape of the fuselage and the vertical stabiliser.
The section also deals with rudder control and its areas of application. The trim, the zero position of the control surfaces for stabilised flight, is discussed. In addition, aerodynamic rudder compensation and the limitations of the rudders at high and low speeds are discussed. Finally, various landing aids such as landing flaps, slats and spoilers are presented and their functions are explained in connection with the improvement of low-speed flight characteristics and the braking effect during landing.
Dangerous flight conditions
This section deals with marginal flight conditions and their effects in flight operations. It emphasises the importance of understanding these conditions during training and being able to react to them correctly. Stalls and spins are particularly emphasised.
Stall / Stall:
A stall occurs when the airflow can no longer follow the profile as the angle of attack increases, leading to a collapse of lift. Pilots must be able to recognise the signs of a stall and recover. The warning signals include buffeting, a stall warning and special markings on the airspeed indicator. When recovering, the elevator is lowered and the engine power is increased to increase speed and restore lift.
Spin:
A spin is a complex flight condition in which the aircraft rotates around a vertical axis, often caused by a one-sided stall. The entry and exit of the spin varies depending on the aircraft type. It is important to follow the specific instructions in the Flight Operations Manual. When initiating a spin, the ailerons and rudder are deflected in opposite directions. To recover, the rudder is applied against the direction of rotation to stop the spin, followed by a correction of the elevator. Spinning harbours the risk of an enormous loss of altitude, especially in a flat spin, which is more difficult to recover from and should therefore be avoided at all costs.
To summarise, understanding and reacting correctly to marginal flight conditions is an important part of pilot training to ensure safety in flight.