# Radio Frequency Interference, Its Mitigation and Its Implications for the Civil Aviation Industry
## 2 Theoretical Background
### Implications for Aviation Systems  
The impacts of RFI on aviation systems are broad and significant:Communication Systems: Interference can result in noise, signal loss, or communication delays between pilots and air traffic controllers.
* Navigation Systems: Disruptions to GPS or radar altimeters can compromise flight path accuracy, particularly during critical operations such as landing or approach.
* Surveillance Systems: Interference with radar systems or transponders can obscure Aircraft positioning, increasing collision risks.
* Recent incidents of radio RFI have significantly impacted aviation operations, highlighting the critical need for robust navigation systems and international cooperation. Two notable examples are given below.  
1. GPS Interference Affecting Finnish Airports (November 2024) [4]: In November 2024, three airports in Eastern Finland--Joensuu, Savonlinna, and Lappeenranta--experienced disruptions in GPS signals, suspected to be caused by Russian interference. This interference compromised the accuracy of navigation systems, prompting Finavia, the Finnish airport operator, to reinstate traditional radio navigation equipment to assist with Aircraft landings. This situation underscores the vulnerability of satellite-based navigation systems to external disruptions and the necessity for alternative navigation aids to ensure aviation safety.  
2. Unauthorized Radio Transmissions in Melbourne, Australia (September 2024): Between July and September 2024, a 45-year-old man in Melbourne allegedly made unauthorized radio transmissions, including fake mayday calls, to commercial Aircraft operating at Melbourne Airport. These transmissions had the potential to endanger Aircraft operations by causing confusion and diverting attention from genuine emergencies. The Australian Federal Police arrested the individual, charging him with offenses that carry significant penalties, emphasizing the serious nature of such interference.  
The above-mentioned incidents illustrate the diverse sources of RFI--from suspected state-sponsored GPS jamming to individual malicious acts--and their profound impact on aviation safety. They highlight the importance of maintaining and updating traditional navigation aids, enforcing stringent regulations against unauthorized transmissions, and fostering international collaboration to mitigate and respond to RFI threats effectively.  
To better understand the safety implications of RFI, fault modes can be classified based on severity and likelihood. For instance, interference with radar altimeters during landing presents a high-severity, moderate-likelihood event due to its impact on altitude accuracy. GPS jamming during enroute flight is moderate in severity but higher in likelihood, especially near conflict zones. Unauthorized radio transmissions fall under moderate severity and low likelihood but can still create confusion. A structured risk matrix can help prioritize mitigation, with high-risk scenarios requiring immediate attention through shielding, redundancy, or alternative aids.  
Aviation communication and navigation systems are vulnerable to both unintentional noise and intentional interference. Common noise sources include atmospheric discharge, cosmic background radiation, and electronic emissions from nearby equipment. These noise elements can degrade the signal-to-noise ratio (SNR), leading to reduced positioning accuracy or missed alerts. To mitigate these issues, systems often employ filtering, low-noise amplifiers (LNAs), and error correction algorithms. For safety-critical operations like ILS or GNSS-based approaches, spectrum management and guard band allocation are also essential in reducing noise overlap with active aviation frequencies.