Information from a European ANSP

• Inbound aircraft is instructed by sector A to contact the next sector B.
• Pilot doesn't establish contact with sector B and realises the problem
• Pilot looks up a frequency for the area he/she is in (on his/her charts), and happens to select the frequency of sector C, subjacent to sector B. This sector happens to expect the aircraft to come to them from sector B after the latter has descended the aircraft to the coordinated level.
• Pilot fails to explain the situation (i.e. lost correct frequency) and doesn't report actual cleared level etc. Sector C assumes the flight was transferred to him by sector B and issues a descent clearance into his airspace.
• Aircraft descends through the traffic of sector B, without any separation assurance from that traffic. Sector B is left with trying to second guess what the flight is doing.

Contributing elements

• Incomplete initial calls from the aircraft (e.g. only stating the call sign) & not explaining they were unable to establish contact with sector B.
• Failure of sector C to recognise the unusually early transfer.
• Sector B doesn't realise that aircraft is lost and has no time to clear aircraft in its vicinity.

Reference

• Radio communication failure procedures are provided in ICAO Annex 10, Volume II, 5.2.2.7.
• European Action Plan for air ground communications safety

Disclaimer

© European Organisation for Safety of Air Navigation (EUROCONTROL) October 2006. This alert is published by EUROCONTROL for information purposes. It may be copied in whole or in part, provided that EUROCONTROL is mentioned as the source and to the extent justified by the non-commercial use (not for sale). The information in this document may not be modified without prior written permission from EUROCONTROL. The use of the document is at the user’s sole risk and responsibility. EUROCONTROL expressly disclaim any and all warranties with respect to any content within the alert, express or implied.