The "Navigation" theory chapter is about how pilots can navigate safely from A to B. Firstly, the earth, the coordinate system and the basics relevant to aviation are explained. Then the various aeronautical charts and their use are described. Building on this, we will discuss how to navigate as a pilot, initially focussing on terrestrial navigation, before moving on to the topic of radio navigation.
The earth and the coordinate system
This theory chapter covers basic concepts of aeronautical navigation and the importance of precise knowledge of the earth's properties and dimensions. It begins with an illustration of the earth's shape and the importance of coordinate systems to clearly define points on the earth's surface.
The rotation of the Earth and its influence on the Earth's shape, in particular the flattening at the poles and the bulge at the equator, are described in detail. This also includes mathematical models and dimensions such as the diameter, circumference and radii of the Earth at various points. The importance of accurate Earth models for technologies such as GPS is also discussed, in particular the geoid and reference ellipsoids.
The section also covers the Earth's coordinate system, including the description of latitude and longitude circles and their importance for navigation. It explains how the latitude and longitude of a location are determined and how distances and differences between different points are calculated.
Various navigationally important lines such as orthodromes, rhumb lines and small circles are described, including their properties and their importance for aeronautical navigation. The section also looks at the differences between true north and magnetic north and explains concepts such as variation and declination.
Finally, various units of measurement in navigation are discussed, including distances, speeds, weights and temperature measurements. The section on time calculation describes the concepts of day length, seasons, different time systems and the use of Coordinated Universal Time (UTC) in aviation.
Aeronautical charts
The AIP VFR (Aeronautical Information Publication for Visual Flight Rules) is an essential resource for pilots applying visual flight rules (VFR). It contains detailed visual flight charts and aerodrome charts for German aerodromes, which are essential for navigation and manoeuvring both on the aerodrome and during the critical phases of approach and departure.
The ICAO 1:500,000 charts are ideal for planning daytime route flights, as they provide a detailed representation of the geography and flight-relevant structures such as aerodromes, navigation aids and airspaces. For night flights, on the other hand, the DFS enroute chart (flight navigation chart) is indispensable. This chart provides an overview of airways, night low-level flight routes and IFR minimum flight altitudes and is specially designed for planning instrument flight rules (IFR) and night flights under visual flight rules.
The aerodrome map contains specific information about an individual aerodrome, including the runways, their surface characteristics, load-bearing capacity and the available take-off and landing distances. It is particularly useful for understanding the local conditions of an aerodrome, including the orientation of the runways.
The height of an aerodrome above sea level (MSL), indicated as "ELEV", can be found on the aerodrome chart. In addition, it can be seen at the top centre of the visual flight chart between the frequencies whether an aerodrome offers the possibility of QDM transmission (magnetic bearing to the aerodrome). The bearings for approach assistance in visual flight charts refer to the magnetic direction, which is important for navigation during the approach.
These charts and information are critical to flight safety and planning and should be thoroughly understood and utilised by pilots flying under VFR.
Terrestrial navigation
In summary, this theoretical section on practical navigation in aviation covers various methods and techniques to help pilots determine their position and make course corrections. Key topics include:
Navigation with the magnetic compass: The magnetic compass is an essential instrument for determining direction. Different types of compass and how they work are explained, including the liquid compass and the backsight compass. Magnetic errors such as deviation and inclination are explained, as well as compass rotation error and acceleration error.
The navigation calculator: This tool facilitates the calculation of navigation tasks. The mechanical navigation calculator is used for various calculations such as speeds, distance/time tasks, fuel calculations and wind triangle tasks.
The wind triangle: A central method for determining the influence of the wind on the flight path. Three basic task types are discussed, in which either the heading, the actual course over ground or the wind are given and the other factors must be determined.
Dead reckoning: This technique enables the location to be determined using data such as speed, course, time and wind. A distinction is made between coupling and uncoupling, whereby the wind influence is taken into account directly when coupling and only at the end when uncoupling.
The 1:60 rule: A useful rule of thumb for calculating the lateral offset caused by the wind. It is based on the assumption that 1 NM lateral offset on 60 NM flight distance corresponds to an angle of 1°.
Determining the turning course: This topic deals with how a reversing course is determined taking the wind into account. The wind correction angle (WCA) is applied twice and in the opposite direction to the counter course of the current heading.
To summarise, this theory chapter places particular emphasis on the practical application of these methods and techniques in real-life flying to ensure safe and efficient navigation.
Radio navigation
This section deals with the central role of radio navigation in professional aviation. Radio navigation, which is based on the use of radio signals to determine positions, set routes and carry out approaches, is indispensable, especially in bad weather. It offers additional safety and accuracy compared to terrestrial navigation. The VFR pilot must familiarise himself with the technical aspects and operation of the on-board equipment. The chapter first covers the technical basics of classic radio navigation, followed by a detailed presentation of various systems and navigation methods. The increasingly important role of satellite navigation is also addressed.
The technical principles cover the working principles based on electromagnetic waves emitted by ground transmitters and received in the aircraft. Different frequency ranges and wavelengths have significant effects on accuracy and interpretation possibilities. Important aspects are electromagnetic wave propagation, modulation and operating modes as well as wave propagation and its interfering factors. Direct waves (quasi-optical waves) differ in their propagation from ground and space waves and are less susceptible to atmospheric interference, but their range is affected by line of sight and obstructions.
Finally, various navigation methods are described, including the use of VHF direction finders (VDF), which are used to determine direction and position in conjunction with radiotelephones. They make it possible to determine directions and positions without special equipment on board, whereby the accuracy and possible sources of error must be taken into account.
The NDB (Non Directional Beacon) is a transmitter that sends out non-directional signals on a fixed frequency. These signals are received by an ADF (Automatic Direction Finder) in the aircraft, which processes the signals via displays in the cockpit. These displays enable navigation by direction finding. NDBs are used in VFR navigation for route navigation and position determination and in IFR for holding and approach procedures. Their widespread use is due to their comparatively low cost.
The ground components of an NDB include a transmitter, a non-directional transmitting antenna and a monitoring system. The on-board components of the ADF include a loop antenna, a sense antenna, a receiver, a control unit and a display unit. NDBs operate in the long and medium wave range, in Germany between 200 kHz and 526.5 kHz.
There are various indicators for interpreting the NDB signals, including the Relative Bearing Indicator (RBI), the Moving Dial Indicator (MDI) and the Radio Magnetic Indicator (RMI). These instruments differ in the way they indicate the direction to the NDB, which is important for correct navigation.
Various navigation procedures with NDBs include the homing procedure, taking a stationary bearing, heading flights and heading cutting. For each of these procedures, the pilot must interpret the NDB signals correctly and navigate accordingly. When flying over an NDB, the display may become unstable, so a constant heading should be maintained until the needle display stabilises.
The VOR (Very High Frequency Omnidirectional Radio Range) is a highly accurate and convenient navigation aid that is favoured by many pilots over the NDB (Non Directional Beacon). The VOR transmits directional radio waves that can be interpreted by the on-board receiver to enable precise navigation. This system is used in both VFR (Visual Flight Rules) and IFR (Instrument Flight Rules) for route navigation, position determination, approach and holding procedures.
The VOR works like a tower that emits two different signals: A sharply focussed beam of light that rotates 360 degrees once per second, and a second signal that is visible in all directions. The position of the observer in relation to the tower can be determined by counting the time between the flash of the signal visible everywhere and the passage of the directional orbital signal. The time measured in seconds corresponds to the direction of the misdirection as seen from the tower.
The VOR transmits two electromagnetic waves at the same frequency: the reference signal and the orbital signal. The reference signal is non-directional and constant, while the orbital signal changes its phase by 1° per 1° on the course rose. This allows the pilot to directly read the QDR (Magnetic Bearing from the station) or QDM (Magnetic Bearing to the station).
Ground components of a VOR include the transmitter, antenna system and monitoring system. The on-board components consist of a receiving antenna, receiver, control unit and display unit. There are two main types of VORs: the conventional VOR (CVOR) and the Doppler VOR (DVOR), with the latter offering greater accuracy.
The range of a VOR depends on the transmission power and the quasi-optical wave propagation. The accuracy of a VOR must not exceed +/-5° in total, whereby the accuracy of the ground station is normally around +/-2° and that of the display unit around +/-1°.
There are various procedures for navigating with a VOR, such as approaching a VOR, flying over a VOR and cutting a course. The VOR displays must be interpreted correctly in order to ensure precise navigation.
Distance Measuring Equipment (DME) is an important component of aeronautical navigation and is used to measure the distance between the aircraft and the ground station. It works in combination with other navigation equipment, such as VOR, and enables a clear position to be determined without the need for a second radio navigation system. The DME system consists of ground and airborne components, which are characterised by transmitting and receiving antennas, transmitters and receivers as well as control and display units.
The function of the DME is based on the time-of-flight measurement of pulses. The on-board device sends interrogation pulses which are received by the ground station, delayed and sent back with a modified frequency. These response pulses are received by the on-board device and used to determine the distance. The measured distance corresponds to the slant range between the aircraft and the ground station. The display is most accurate at a greater distance from the ground station and becomes less accurate as the aircraft approaches the station. During overflight, the DME displays the vertical distance to the station.
DME systems operate in the UHF frequency range and are usually combined with VORs. They can also be connected to NDBs, ILS systems or military TACAN systems. Sources of error in DME include shadowing in cross-axis positions and potential interference with signals from other ground stations.
It also explains the radar system and its role in aviation, including primary and secondary radar (SSR). Radar systems use electromagnetic waves to determine the position and range of flying objects, with primary radar based on reflection and secondary radar based on an onboard response system. SSR provides more detailed information such as flight altitude and aircraft identification code. The technology has developed considerably since its inception and is an essential tool for air traffic control. Sources of error in radar operation include shadowing and the limitation of radar detection by the radar horizon and the cone of silence.
Finally, the transponder functions and modes required for communication with the secondary radar are described. Different transponder codes are used for specific situations, such as emergencies or hijacking, and there are provisions for using the transponder in different flight areas and situations. Mode S transponders offer additional functions such as data link communication to reduce radio traffic.
Furthermore, the functionality and components of satellite navigation systems, in particular the Global Positioning System (GPS), are described. A distinction is made between three main segments of the GPS system:
1st ground segment: Consists of the main control station and various monitoring stations worldwide. These stations monitor the overall system, calculate satellite orbits and transmit correction data to the satellites.
2nd space segment: Comprises several satellites in different orbits that transmit signals to determine position, time and speed. At least 24 satellites must be active for complete coverage.
3rd on-board segment: Contains the receiving antenna, the receiver and the display and control unit in the aircraft.
The chapter also deals with the accuracy of the GPS system and possible interference, such as atmospheric influences and shadowing by terrain or aircraft parts. The accuracy of GPS data without interference factors is around 70-100 metres. Furthermore, the possibility of the US government to reduce the accuracy of the system (Selective Availability) is explained.
For navigation with GPS, at least four satellites must be received in order to determine a three-dimensional position (including altitude). In addition, the need for an up-to-date database in the GPS device and the importance of correctly setting the coordinate system are emphasised.
Finally, the "Emergency Locator Transmitter" (ELT), an emergency and accident locator transmitter in aviation that is triggered manually or automatically in the event of an impact and transmits on specific frequencies, is discussed. ELT emergency signals are transmitted via the COSPAS-SARSAT system to ground control centres, which are integrated into the GEOSAR and LEOSAR satellite systems.