What aircraft was involved and where did it happen?

The accident on 1995-03-13 involved a aircraft, registration OH-LMZ, at FI.

What was the probable cause of the accident?

The primary cause of the radio interference was a short circuit resulting from the accidental severing of an unmarked underground telephone cable during excavation work, compounded by substandard previous repairs and a lack of proper cable identification.

Radio Communication Failure at Ivalo Airport

A short circuit in the primary VHF radio system at Ivalo Airport caused significant radio interference and a total loss of the primary frequency for nearly an hour.

What happened

On March 13, 1995, at approximately 13:45 UTC, a serious safety incident occurred at Ivalo Airport involving a total failure of the primary VHF radio frequency (118.00 MHz). The incident began while a Finnair DC-9-82 (OH-LMZ) was performing an ILS approach to runway 22. Simultaneously, two Finnish Air Force Saab 35 Draken aircraft, callsigns L-45 and G-57, were conducting instrument approaches to the same runway.

During the approach phase, the primary frequency became unusable due to continuous interference. The frequency experienced interference for approximately 1 hour and 35 minutes, with the channel being completely out of service for about 52 minutes. While the air traffic controller managed to communicate with some aircraft using a backup radio, the interference consisted of loud whistling, buzzing, and unintelligible speech, making clear communication nearly impossible. The controller instructed the aircraft to land or perform go-arounds as necessary due to the degraded radio conditions.

The investigation

The investigation focused on identifying the source of the interference and the cause of the communication breakdown. Investigators examined the radio equipment, the physical telephone cable infrastructure, and the maintenance records of the airport's communication systems. The investigation also looked into the reporting procedures used by the air traffic controller and the quality of previous repairs made to the underground cabling.

Findings

The primary cause of the interference was a short circuit in the radio system's telephone cable.
The failure was triggered by excavation work that severed an unmarked underground telephone cable.
Subsequent inspections of the cable revealed that previous repair work had been performed unprofessionally, with significant errors including insufficient heat-shrinking of connectors, improper use of Vaseline on conductors, and incorrect wiring sequences.
There was a lack of proper cable mapping and marking in the field, making it difficult to locate the damaged line.
The air traffic controller did not file a formal safety report regarding the malfunction at the time of the event, intending to leave a note for the next shift instead.
There was no established minimum equipment standard for radio monitoring capabilities at state-run aerodromes to ensure controllers could monitor both primary and backup frequencies simultaneously.