Incident Overview
On November 7, 2017, an incident was recorded in the Terminal Maneuvering Area (TMA) of Gran Canaria (GCLP). The event involved a Boeing 737-800 operated by Enter Air. The investigation was conducted by the user’s commission and concluded on May 22, 2018. No injuries were reported among the personnel involved.
Operational Context
The flight crew of Enter Air flight ENT7361 was executing a STAR approach under vector control due to signal reception limitations for the DVOR/DME 'GDV' below FL150. After passing waypoint ISORU, the crew received clearance to descend to FL130 and subsequently to 6,000 feet. The controller instructed them to intercept radial 160 degrees after passing waypoint GDV.
Sequence of Events
During this phase, Enter Air flight TVP7311 departed GCLP and climbed to 3,000 feet before receiving clearance to climb to FL120. Simultaneously, another aircraft, ENT5073, was present on the same frequency as ENT7361 and received a heading change instruction for approach. The crew of ENT7361 mistakenly accepted this heading change command intended for ENT5073.
The controller detected an overlap in communications and attempted to identify the unauthorized station. When ENT7361 began executing the incorrect left turn near waypoint TODKO, the controller issued a correction to resume the track to GDV. To ensure separation between the climbing TVP7311 and the descending ENT7361, the controller ordered TVP7311 to level off at FL70 and instructed ENT7361 to descend to FL90.
Separation Status
ENT7361 complied with the correction and resumed its track to GDV. At a point 9 NM from GDV, while at FL127, the controller informed the crew of ENT7361 that they were operating outside their clearance. TVP7311 was then cleared to continue climbing to FL120 toward waypoint LARYS. The horizontal separation between the two aircraft was recorded as 5.9 NM, with a vertical separation of 5,100 feet.
Investigation Findings
The investigation identified two primary factors contributing to the incident. First, the simultaneous presence of two Enter Air aircraft with similar call signs (ENT7361 and ENT5073) on the same frequency created confusion. Second, the crew of ENT7361 erroneously accepted a heading change instruction that was directed at the other aircraft.
Safety Actions
The operator implemented preventive measures, including the assignment of letter prefixes to flight numbers when similar call signs are active in the same sector. Additionally, the results of the investigation were published in a safety bulletin to enhance awareness within the organization.