What aircraft was involved and where did it happen?

The accident on 2005-11-13 involved a A-320, at FIR Praha, CZ.

What was the probable cause of the accident?

The incident was caused by the flight crew's failure to establish required radio contact with air traffic control when entering the Bratislava and Prague Flight Information Regions, despite having the necessary flight plan information to do so.

Airbus A320 enters Czech airspace without radio contact

An Armavia Airlines flight flying from Armenia to the Netherlands entered the Prague Flight Information Region without establishing communication with air traffic control.

What happened

On November 13, 2005, an Airbus A320-211, operating as flight RNV 151 for Armavia Airline Company Co. Ltd, entered the Prague Flight Information Region (FIR LKAA) without establishing radio contact with ACC Praha. The aircraft was performing a scheduled flight from Yerevan, Armenia (UDYZ) to Amsterdam, Netherlands (EHAM) at flight level 360.

While operating in the Budapest FIR (LHCC), the crew received instructions from Budapest ACC on frequency 136.375 MHz to proceed directly to the LITKU waypoint. However, after passing LITKU, the crew did not receive a subsequent instruction to change frequencies. Consequently, the crew continued through the Bratislava FIR (LZBB) and into the Prague FIR (LKAA) while remaining on the Budapest ACC frequency.

Upon realizing the aircraft had not established contact, Bratislava ACC notified Prague ACC. In response, the Czech Air Force scrambled alert fighters to identify the aircraft. During the interception, the crew observed the military aircraft and eventually established communication via another aircraft operating in the Budapest FIR, which relayed instructions to switch to the appropriate frequencies.

The investigation

The ÚZPLN investigation examined the flight's progress, the crew's actions, and the response of air traffic services. The investigation reviewed the crew's flight planning, the communication logs from ACC Budapest, ACC Bratislava, and ACC Praha, as well as the interception procedures performed by the NATINEADS alert aircraft. The investigation also confirmed that all radio and navigation systems on the aircraft were functioning normally and that weather conditions were not a factor.

Findings

The crew failed to establish radio contact with ACC Praha at the ODOMO entry point into the Prague FIR.
The crew did not implement any standard lost communication procedures.
The crew failed to utilize their flight plan information to identify the appropriate entry/exit waypoints and contact the relevant air traffic services as required by regulations.
The primary cause of the incident was the crew's failure to establish the required communication while transiting through Class C airspace.
Air traffic controllers in Prague performed all necessary actions and coordination in accordance with established protocols for handling lost communications, including notifying neighboring sectors and coordinating with military authorities.