Center Controller training instructors reported getting distracted and complacent while having a discussion on ATC procedures and did not notice that the Radar Assistant Trainee did not provide proper separation between two aircraft. The trainer then intervened and issued a heading to prevent the potential NMAC.
Synopsis
Center Controller training instructors reported getting distracted and complacent while having a discussion on ATC procedures and did not notice that the Radar Assistant Trainee did not provide proper separation between two aircraft. The trainer then intervened and issued a heading to prevent the potential NMAC.
Narrative
OJT was being performed on the Radar and the Radar Assistant positions. The Radar Assistant Trainee was on their 2nd session at the incident sectors. They had asked pertinent questions such as; 'How long of a void time do we normally give at airports where we provide Approach Control service?' and 'What altitudes do we normally give initially as part of departure clearances?'. This led to a discussion between myself; the other OJTI and the Radar Assistant Trainee regarding our techniques. At the time we were working in a combined sector with approximately 5 aircraft total. Only 2 of the aircraft were even remotely close; Aircraft X and Aircraft Y. Aircraft Y was in an enroute descent to the bottom of our airspace; 11000 ft.; to be transferred to an underlying Approach Control. Aircraft X was a departure on their initial climb-out and handed to us by a different sector at the same Approach Control. This is a very; very; very common conflict. The Radar Trainee indicated that they recognized the crossing traffic by putting a 3 NM halo on one of the aircraft. The Radar Assistant understood this to mean that the Radar Trainee had a plan.The 2 OJTIs distracted each other with the ongoing discussion of procedures at the sector. Our attention was brought to the conflict when ZZZ shouted on our landline to ask if we were aware of the impending conflict. Concurrently; the ZZZ1 Radar Controller also yelled over the same question. Myself and the other OJTI were slow to react; because when we looked at the situation on the scope we were stunned at what we saw; and quite frankly couldn't understand how the situation had deteriorated so quickly. About this time Aircraft Y was leaving 16600 ft. for 11000 ft; Aircraft X was leaving 13800 ft. for 23000 ft. The Radar Trainee issued 15000 ft. to Aircraft Y. This further confused the OJTIs because Aircraft X when handed to us from Approach would have been climbing to 14000 ft. So for a valuable moment we assumed the Radar Trainee had not climbed Aircraft X. Aircraft X's next hit was leaving 14200 ft. In the Radar Trainee's panic they had made the situation much worse by removing the possibility that the aircraft could swap out; which was the safest solution absent appropriate lateral separation. The Radar Trainee tried to turn the aircraft; but used the wrong call sign for Aircraft Y. The Radar OJTI intervened and issued a heading that may have prevented a NMAC.Recommendations - none. The 2 OJTIs have nearly 50 years experience combined and are well aware that lack of attention when providing OJT is a national issue. Despite that we got lulled into inattention due to the very low workload and failed to perform successfully.
Second reporter narrative
I was training my Radar Trainee at the time. My trainee is on their last two radar positions. Traffic was light; about 6 planes between two combined sectors and the only complexity was between the two aircraft involved. Aircraft X departed ZZZ and was headed to ZZZZZ climbing to 14000 ft. Aircraft Y had descended to 11000 ft. toward ZZZ1 landing ZZZ2. Prior to this I had been having a discussion about a route change that we had issued to an aircraft earlier in the session with the D-side Trainer sitting next to me at the same sector. Admittedly this discussion pulled too much of my attention away from the scope. My trainee had recognized the conflict and began implementing a plan to separate the aircraft and I did not do a good enough job monitoring the situation to confirm that the plan was going to work. My trainee turned both Aircraft Y and Aircraft X left. I then heard my trainee stop Aircraft Y at 15000 ft. but they did not stop Aircraft X at 14000 ft.This immediately caught my attention and I looked back to realize it was not going to work. I told my trainee to turn Aircraft Y further left and expedite descent to 11000 ft. The clearance was issued right away and Aircraft Y complied. I then tried to override and turn Aircraft X further left but my call was stepped on by another aircraft on frequency. Soon after this I believe minimum separation was lost between Aircraft X and Aircraft Y. Due to Aircraft Y descending rapidly through 13000 ft.; separation was achieved again and both aircraft were returned to their flight plan routes.I was too complacent with allowing my trainee to handle the situation without confirming the plan would work. I should have waited to make sure the vectors were going to be enough before continuing my conversation with the other trainer.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.