Narrative:

I was acting as on the job training instructor (ojti) for a developmental controller on the terminal control position. Another controller was acting as our handoff. Denver center requested aircraft X to enter our airspace at FL170 and outside of the arrival gate. Handoff approved this request from ZDV. I did not hear the request and handoff did not ask me or the developmental if we would approve it. Aircraft X checked on and was kept at FL170 and given a heading of 110 to be sequenced. On heading 110; aircraft X must be kept at or above FL170 because the heading took him directly over our SID which takes departures to FL160. The developmental keyed up to descend aircraft X to FL160 and during the transmission I raised my voice at the developmental to keep the aircraft at FL170. The trainee corrected his instruction to FL170 in the same transmission and aircraft X did not hear it. Aircraft X responded before the developmental had said FL170 and therefore they were talking at the same time. Aircraft X was heard on the tapes saying '...six-thousand...' aircraft X went on to make a suggestion that I proceed straight-in VFR to the airport and was told to continue heading 110 but was again told to descend to FL160 by the trainee. I corrected him again; the developmental corrected himself but aircraft X was already descending from the first time he was told FL160. I stepped in; issued a traffic alert to aircraft X and instructed him to climb immediately. Aircraft X lost lateral and vertical separation with a departure aircraft Y. I reviewed the tapes with the atm [air traffic manager] and saw on the replay that they came within 1.48 miles and 600 feet of each other. Better communication on the part of handoff controller. Better control of the situation by me; the ojti. Better listening on my part and developmental's part to ensure correct read back of instructions.

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Original NASA ASRS Text

Title: ASE TRACON Instructor and Developmental reported of a loss of separation due to a read back error. Developmental descended an aircraft incorrectly; Instructor caught it and told Developmental to fix it. While transmitting the pilot transmitted also responding to descent given in error. Separation was lost between arrival an missed approach aircraft.

Narrative: I was acting as On the Job Training Instructor (OJTI) for a developmental controller on the terminal control position. Another controller was acting as our handoff. Denver Center requested Aircraft X to enter our airspace at FL170 and outside of the arrival gate. Handoff approved this request from ZDV. I did not hear the request and handoff did not ask me or the developmental if we would approve it. Aircraft X checked on and was kept at FL170 and given a heading of 110 to be sequenced. On heading 110; Aircraft X must be kept at or above FL170 because the heading took him directly over our SID which takes departures to FL160. The developmental keyed up to descend Aircraft X to FL160 and during the transmission I raised my voice at the developmental to keep the aircraft at FL170. The trainee corrected his instruction to FL170 in the same transmission and Aircraft X did not hear it. Aircraft X responded before the developmental had said FL170 and therefore they were talking at the same time. Aircraft X was heard on the tapes saying '...six-thousand...' Aircraft X went on to make a suggestion that I proceed straight-in VFR to the airport and was told to continue heading 110 but was again told to descend to FL160 by the trainee. I corrected him again; the developmental corrected himself but Aircraft X was already descending from the first time he was told FL160. I stepped in; issued a traffic alert to Aircraft X and instructed him to climb immediately. Aircraft X lost lateral and vertical separation with a departure Aircraft Y. I reviewed the tapes with the ATM [Air Traffic Manager] and saw on the replay that they came within 1.48 miles and 600 feet of each other. Better communication on the part of handoff controller. Better control of the situation by me; the OJTI. Better listening on my part and developmental's part to ensure correct read back of instructions.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.