What happened
While operating in the Gander ACC sector, two aircraft, Elite 5512 and Elite 5516, were monitoring the same radio frequency. A Gander controller issued an instruction to Elite 5512 to contact Moncton ACC on a new frequency. However, the crew of Elite 5512 did not hear or acknowledge this instruction. Instead, the first officer of Elite 5516 responded to the instruction, omitting the aircraft's call sign in the transmission.
During this frequency change, the captain of the Boeing 757, registration Elite 5516, was not present on the flight deck. The first officer requested and received clearance to climb to FL390. At the Moncton ACC, a controller trainee was managing the Heath Point Sector under the supervision of an on-the-job instructor (OJI). The trainee observed a radar target labeled Elite 5512 and, upon hearing the radio contact from Elite 5516, mistakenly believed the two were the same aircraft. Despite the pilot mentioning another Elite aircraft was airborne, the trainee issued the climb clearance to the wrong target. The error was only caught when the OJI, momentarily distracted by a tour group in the facility, noticed the Elite 5512 target had failed to climb and subsequently ordered the aircraft back down to FL 370.
The investigation
Investigators examined the communications tapes from Gander ACC and the radar configurations at Moncton ACC. The investigation established that the radar display was set to show data tags only for aircraft within the Heath Point Sector, meaning the track for Elite 5516 was not visible to the trainee at the time of the clearance. The investigation also reviewed the Standard Operating Procedures (SOP) for the Boeing 757, noting that the flight crew should have confirmed altitude changes. Furthermore, the investigation looked into the supervisory environment, noting that the OJI was distracted by a group of former Transport Canada employees touring the center during the hand-off.
Findings
- The primary cause of the loss of separation was that the OJI was not properly monitoring the controller trainee during the issuance of the climb clearance.
- The controller trainee failed to verify that the aircraft on the radar matched the aircraft on the radio, relying on an incorrect assumption due to previous experiences with erroneous radar data.
- The first officer of Elite 5516 used improper phraseology by failing to include the aircraft's call sign in the response.
- The Gander controller did not catch the identification error during the initial hand-off.
- The presence of a tour group diverted the instructor's attention from his supervisory duties.
- The flight crew's failure to follow SOPs regarding altitude change verification contributed to the error.
- Light traffic volume may have contributed to a sense of complacency among both the trainee and the instructor.