The subject of radio navigation provides the knowledge required to use radio navigation aids effectively and to navigate safely through controlled and uncontrolled airspace. Radio navigation covers a wide range of technologies and concepts, from classic ground radio stations to modern satellite navigation systems. This article provides an overview of the content of this subject. It is important to emphasise that this is only part of the content covered in the theory training.
Basics of radio technology
1. electromagnetic waves
- Definition:
- Radio waves are electromagnetic waves that are used to transmit information.
- Properties:
- Frequency (Hz): Determines the wavelength. The higher the frequency, the shorter the wavelength. Frequencies in the VHF range (Very High Frequency) are particularly relevant for aviation.
- Amplitude: Affects the signal strength and range.
- Phase modulation: Used by certain navigation systems such as VOR to transmit directional information.
2. signal propagation
- Direct waves:
- Utilise the line of sight between transmitter and receiver. They are crucial for systems such as VOR and ILS.
- Bumps in the road:
- Track the curvature of the earth and are used at low frequencies like NDBs. Their range depends on the ground conductivity.
- Ionospheric waves:
- Reflect off the ionosphere and can be used over long distances. However, they play a lesser role in modern navigation.
3. interference and disturbances
- Natural influences:
- Weather conditions such as thunderstorms can scatter or attenuate radio waves.
- Technical faults:
- Interference from other radio transmitters, especially in urban areas.
Ground radio stations
1 NDB and ADF
- NDB (Non-Directional Beacon):
- Simple ground stations that emit a non-directional signal.
- Works in the long wave range (LF) and lower medium wave range (MF).
- ADF (Automatic Direction Finder):
- On-board instrument that indicates the direction to the NDB. It is particularly relevant in regions without modern radio navigation aids.
- Restrictions:
- Susceptible to atmospheric disturbances and night-time interference, which can affect accuracy.
2. VOR (VHF Omnidirectional Range)
- Species:
- CVOR (Conventional VOR): Sends a signal with a constant frequency.
- DVOR (Doppler VOR): Improves accuracy through the Doppler effect by rotating transmitters around the centre of the station.
- Function:
- Enables pilots to determine their position relative to the station using radials (courses).
- Range:
- Depending on the flight altitude and line of sight.
3 DME (Distance Measuring Equipment)
- Function:
- Measures the distance between the aircraft and the ground station.
- Working method:
- Transmits a signal from the aircraft to the station, which is reflected. The transit time is used to calculate the distance.
- Combination with VOR:
- Often integrated to provide simultaneous direction and distance information.
4. instrument landing system (ILS)
- Components:
- Localiser: Leads horizontally to the centre of the runway.
- Glide Slope: Leads vertically along an ideal approach angle (usually 3°).
- Categories:
- CAT I, II and III differ in the minimum visibility conditions for the approach.
5 MLS (Microwave Landing System)
- Advantages:
- More flexible approach angles and routes, especially in complex airport environments.
- Disadvantages:
- High costs and low distribution compared to ILS.
Radar
1. basics
- Function:
- Uses reflected electromagnetic waves for localisation and distance measurement.
- Species:
- Primary radar: Recognises objects based on reflected waves.
- Secondary radar (SSR): Uses transponders on board for identification and altitude transmission.
2. ground radar
- Areas of application:
- Traffic monitoring at the airport and control of arrivals and departures.
3. weather radar
- Function:
- Recognises precipitation, turbulence and other weather phenomena.
Area Navigation Systems (RNAV)
1. definition and mode of operation
- RNAV:
- Enables navigation along flexible routes, independent of ground stations.
- Components:
- GPS, INS (Inertial Navigation System), VOR/DME.
2. basics of the FMS (Flight Management System)
- Functions:
- Automation of route planning, power calculation and navigation customisation.
Performance-Based Navigation (PBN)
1. basics
- RNAV:
- Enables flexible flight route planning.
- RNP (Required Navigation Performance):
- Strict accuracy requirements, especially in complex airspaces.
2. specifications
- RNAV 10: For long-haul flights over oceans.
- RNP 1 and 2: For high-precision navigation in terminal areas.
GNSS (Global Navigation Satellite Systems)
1. GPS (Global Positioning System)
- Functionality:
- Triangulation with signals from at least four satellites.
2. other systems
- Galileo: European system with high accuracy.
- GLONASS: Russian alternative to GPS.
- BeiDou: Chinese system with global reach.
Conclusion
The subject of radio navigation provides essential knowledge for using modern navigation systems safely and effectively. It combines traditional procedures with new technologies and ensures that pilots can navigate flexibly and precisely. Comprehensive training in these areas is essential for safe flight operations in instrument flight.
Source references:
EASA FCL