What is BFO on Airbus A320? (Beat Frequency Oscillator)

The Beat Frequency Oscillator, commonly known as the BFO, is an essential component of the Airbus A320 aircraft that plays a crucial role in ensuring accurate navigation and communication. The BFO is a type of radio receiver that helps pilots locate and communicate with ground-based navigation aids, such as VHF omnidirectional range (VOR) stations and instrument landing systems (ILS).

The BFO on the Airbus A320 is responsible for providing the necessary signal for the aircraft’s communication and navigation systems to function properly. It works in conjunction with other avionic systems to provide reliable and accurate information to the flight crew.

How Does the Beat Frequency Oscillator Work?

The Beat Frequency Oscillator operates by generating a local oscillator signal that combines with the received signal from a navigation aid. The resulting beat frequency is then processed to extract the navigation information. This information is displayed to the flight crew or used by other systems for navigation purposes.

The BFO relies on the principle of heterodyning, which involves mixing two frequencies to create a third frequency. In this case, the received frequency from the navigation aid and the local oscillator frequency are mixed to create the beat frequency. The beat frequency is the difference between the two input frequencies and carries the navigational information.

For example, when the BFO is receiving a signal from a VOR station at a frequency of 112.00 MHz, the local oscillator frequency might be set at 111.80 MHz. The resulting beat frequency would then be 200 kHz, which can be used to determine the aircraft’s position relative to the VOR station.

The Importance of the Beat Frequency Oscillator

The Beat Frequency Oscillator plays a critical role in the navigation and communication systems of the Airbus A320 aircraft. It ensures that the flight crew has accurate and reliable information about their position and allows them to safely navigate through various phases of flight.

One of the primary applications of the BFO is in the Automatic Direction Finder (ADF) system. The ADF system uses the BFO to receive signals from non-directional beacons (NDBs), which are ground-based radio transmitters that emit signals on a specific frequency. By comparing the received signal with the local oscillator signal, the BFO allows pilots to determine the direction of the NDB and navigate accordingly.

The BFO also plays a crucial role in the Instrument Landing System (ILS), a precision approach system widely used in modern aviation. The ILS helps guide the aircraft to the runway during low visibility conditions. The BFO receives the signal from the ILS localizer and glideslope antennas, allowing the flight crew to maintain the correct course and descent path for a safe landing.

Furthermore, the BFO ensures reliable communication with air traffic control (ATC) through the VHF communication system. By generating the necessary frequencies and processing the signals, the BFO allows pilots to maintain clear and effective communication with ATC, receiving important instructions and providing updates about the aircraft’s position and intentions.


The Beat Frequency Oscillator, or BFO, is a crucial component of the Airbus A320 aircraft’s navigation and communication systems. It works by mixing the received signal from navigation aids with a local oscillator signal to generate a beat frequency that carries navigational information. The BFO allows pilots to accurately determine the aircraft’s position, navigate using non-directional beacons, and perform precision approaches during landing.

Without the BFO, the Airbus A320’s navigation and communication systems would be compromised, hindering the ability of the flight crew to safely operate the aircraft. It is a testament to the importance of this component in modern aviation and its role in ensuring efficient and reliable air travel.

For More: What is MFA on Airbus A320? (Memorized Fault Annunciator)