<< >> NASA ASRS Report 1507519, December 2017

S46 TRACON controller reported separation was lost; before pilot applied visual separation was obtained.

Attributes
ACN	1507519
Time
Date	201712
Local Time Of Day	1801-2400
Place
Locale Reference	S46.TRACON
State Reference	US
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	Visual Approach
Flight Plan	IFR
Aircraft 2
Make Model Name	Light Transport
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	Visual Approach
Flight Plan	IFR
Person 1
Function	Approach Instructor
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 3
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy

Narrative:

Training was in progress on final. We received notification aircraft X was a medical emergency from the southwest. I told the plan to my trainee; we would descend the aircraft on the approach to 16R to 2100 feet to allow aircraft X descend for the visual approach. I also instructed the trainee to vector aircraft X through the bay for the right base. I told him to start issuing traffic for pilot applied visual separation. Aircraft X reported aircraft Z; a B737; in sight and told to maintain visual separation from the B737; we received a confirmation from aircraft X for pilot applied visual separation. Aircraft Y reported aircraft X insight; was told to maintain visual separation from aircraft X; we did not receive a confirmation. Separation was lost before pilot applied visual separation was obtained. Aircraft X was cleared for a visual approach to 16L and began a descent while crossing over the top of aircraft Y. Aircraft Y notified us he received a RA from aircraft X.

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Original NASA ASRS Text

Title: S46 TRACON Controller reported separation was lost; before pilot applied visual separation was obtained.

Narrative: Training was in progress on Final. We received notification Aircraft X was a medical emergency from the southwest. I told the plan to my trainee; we would descend the Aircraft on the approach to 16R to 2100 feet to allow Aircraft X descend for the visual approach. I also instructed the trainee to vector Aircraft X through the bay for the right base. I told him to start issuing traffic for pilot applied visual separation. Aircraft X reported Aircraft Z; a B737; in sight and told to maintain visual separation from the B737; we received a confirmation from Aircraft X for pilot applied visual separation. Aircraft Y reported Aircraft X insight; was told to maintain visual separation from Aircraft X; we did not receive a confirmation. Separation was lost before pilot applied visual separation was obtained. Aircraft X was cleared for a visual approach to 16L and began a descent while crossing over the top of Aircraft Y. Aircraft Y notified us he received a RA from Aircraft X.

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.