Sct instructor while instructing developmental had a loss of separation due to developmental clearin...

Attributes
ACN	1337214
Time
Date	201603
Local Time Of Day	0001-0600
Place
Locale Reference	SCT.TRACON
State Reference	CA
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	SR22
Operating Under FAR Part	Part 91
Flight Phase	Descent
Route In Use	Visual Approach
Flight Plan	IFR
Aircraft 2
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	Climb
Flight Plan	IFR
Person 1
Function	Approach Departure Instructor
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 4
Events
Anomaly	ATC Issue All Types Airspace Violation All Types Conflict Airborne Conflict Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Inflight Event / Encounter CFTT / CFIT
Miss Distance	Vertical 800

Narrative:

We were training on delmar. Aircraft X was at 4;000 east of okb. Aircraft Y was coming missed off okb climbing eastbound toward aircraft X. I told the trainee to stop aircraft Y at 3;000 to ensure separation. The trainee cleared aircraft X for the visual and switched him to the tower.even though; we hadn't ensured separation from the two aircraft; I thought aircraft X would pull away from aircraft Y because of his speed and turn toward the airport. Instead; the aircraft X slowed down and widened out to the north. I told the trainee to turn aircraft Y below the minimum vectoring altitude (MVA) to ensure separation. We then had to call tower and ask them to square the base turn of aircraft X so he wouldn't turn back into our aircraft Y.in the future; I need to consider trainee hours when working a position. I'm really vigilant at ensuring separation; however; when the trainee cleared aircraft X for the visual; even though I wouldn't have done it so soon; I assumed that aircraft X would turn toward the airport and wouldn't slow until he was close to the runway. I shouldn't assume this; every pilot flies their plane differently; however I didn't even consider aircraft X would widen out to the north.the trainee definitely learned that they need to control this approach to ensure separation from okb.

Original NASA ASRS Text

Title: SCT Instructor while instructing developmental had a loss of separation due to developmental clearing an aircraft for a visual approach while another aircraft was in close proximity.

Narrative: We were training on Delmar. Aircraft X was at 4;000 east of OKB. Aircraft Y was coming missed off OKB climbing eastbound toward Aircraft X. I told the trainee to stop Aircraft Y at 3;000 to ensure separation. The trainee cleared Aircraft X for the visual and switched him to the Tower.Even though; we hadn't ensured separation from the two aircraft; I thought Aircraft X would pull away from Aircraft Y because of his speed and turn toward the airport. Instead; the Aircraft X slowed down and widened out to the north. I told the trainee to turn Aircraft Y below the Minimum Vectoring Altitude (MVA) to ensure separation. We then had to call Tower and ask them to square the base turn of Aircraft X so he wouldn't turn back into our Aircraft Y.In the future; I need to consider trainee hours when working a position. I'm really vigilant at ensuring separation; however; when the trainee cleared Aircraft X for the visual; even though I wouldn't have done it so soon; I assumed that Aircraft X would turn toward the airport and wouldn't slow until he was close to the runway. I shouldn't assume this; every pilot flies their plane differently; however I didn't even consider Aircraft X would widen out to the north.The trainee definitely learned that they need to control this approach to ensure separation from OKB.

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.

Sct instructor while instructing developmental had a loss of separation due to developmental clearing an aircraft for a visual approach while another aircraft was in close proximity.