Seattle TRACON controller reported that while instructing; the sector became overloaded and aircraft...

Narrative:

Training on both departure sectors combined; trainee is a certified professional controller in training cpc-it supervisor with years of air traffic experience. South flow; MVFR; multiple layers with bases around 2;000' and tops around 10;000'.the trainee released multiple aircraft off bfi; which combined with sea departures to create a complex situation which was beyond their capability. I had to take over the position with numerous situations developing; the first of which was aircraft X and aircraft Y. Aircraft X was a bfi departure to bfi; but needed to climb to 15;000' to check a system before returning. Aircraft Y's SID off sea includes an automatic turn to the east; which brought him in conflict with aircraft X who had been left runway heading off bfi. After taking over; I determined aircraft X's intentions and initiated a turn away from aircraft Y and a climb; but it was too late to maintain separation. This led into the next portion of the incident; because I did not climb aircraft Y. I was attempting to recover from the loss with aircraft X. A few moments later; I became aware that aircraft Y was at 5;000' and about to enter a 5;700' MVA. I instructed aircraft Y to turn and climb; but it was too late to avoid the higher MVA. The final portion of the incident was in all of this I had turned a subsequent bfi departure; aircraft Z; to the east as well. I did not climb aircraft Z and by the time I was aware of it the aircraft was at 3;000' in a 5;000' MVA. I issued instructions for aircraft Z to make a left turn to the northwest; which I knew would parallel terrain in the area; and climb immediately.to my knowledge; all aircraft involved subsequently proceeded without further incident. Management was immediately aware of the incidents.the root cause of the incident(s) is my failure as an on the job training instructor (ojti) to keep the situation under positive control. I should not have allowed the trainee to release so many bfi departures. My intention was to allow the releases to add some complexity and increase the workload slightly; which would provide an opportunity for me to discuss with the trainee later how it can be smarter to allow fewer releases and have the traffic be more manageable instead. Each release adds complexity to the situation and I was not as aware as I should have been of the specifics of each aircraft the trainee released. Specifically; I would not have released aircraft X without asking the bfi controller if they were aware of the aircraft's intentions. Knowing ahead of time that aircraft X wanted to maneuver in the airspace at 15;000' would have allowed better planning. I also should have taken over the position much sooner. I was overconfident in both my ability to recover the sector; as well as the trainee's ability to work the traffic. I was lulled into a false sense of security by the trainee's previous experience and overall performance on the previous training session. I was not aware that the trainee had only a few hours on either departure sector. Had I been aware of that fact; I should have requested the departure sectors be split instead of training on both sectors combined.

Original NASA ASRS Text

Title: Seattle TRACON Controller reported that while instructing; the sector became overloaded and aircraft where in Minimum Vectoring Areas below the required altitudes.

Narrative: Training on both departure sectors combined; trainee is a Certified Professional Controller in Training CPC-IT supervisor with years of air traffic experience. South flow; MVFR; multiple layers with bases around 2;000' and tops around 10;000'.The trainee released multiple aircraft off BFI; which combined with SEA departures to create a complex situation which was beyond their capability. I had to take over the position with numerous situations developing; the first of which was Aircraft X and Aircraft Y. Aircraft X was a BFI departure to BFI; but needed to climb to 15;000' to check a system before returning. Aircraft Y's SID off SEA includes an automatic turn to the East; which brought him in conflict with Aircraft X who had been left runway heading off BFI. After taking over; I determined Aircraft X's intentions and initiated a turn away from Aircraft Y and a climb; but it was too late to maintain separation. This led into the next portion of the incident; because I did not climb Aircraft Y. I was attempting to recover from the loss with Aircraft X. A few moments later; I became aware that Aircraft Y was at 5;000' and about to enter a 5;700' MVA. I instructed Aircraft Y to turn and climb; but it was too late to avoid the higher MVA. The final portion of the incident was in all of this I had turned a subsequent BFI departure; Aircraft Z; to the East as well. I did not climb Aircraft Z and by the time I was aware of it the aircraft was at 3;000' in a 5;000' MVA. I issued instructions for Aircraft Z to make a left turn to the Northwest; which I knew would parallel terrain in the area; and climb immediately.To my knowledge; all aircraft involved subsequently proceeded without further incident. Management was immediately aware of the incidents.The root cause of the incident(s) is my failure as an On the Job Training Instructor (OJTI) to keep the situation under positive control. I should not have allowed the trainee to release so many BFI departures. My intention was to allow the releases to add some complexity and increase the workload slightly; which would provide an opportunity for me to discuss with the trainee later how it can be smarter to allow fewer releases and have the traffic be more manageable instead. Each release adds complexity to the situation and I was not as aware as I should have been of the specifics of each aircraft the trainee released. Specifically; I would not have released Aircraft X without asking the BFI controller if they were aware of the aircraft's intentions. Knowing ahead of time that Aircraft X wanted to maneuver in the airspace at 15;000' would have allowed better planning. I also should have taken over the position much sooner. I was overconfident in both my ability to recover the sector; as well as the trainee's ability to work the traffic. I was lulled into a false sense of security by the trainee's previous experience and overall performance on the previous training session. I was not aware that the trainee had only a few hours on either departure sector. Had I been aware of that fact; I should have requested the departure sectors be split instead of training on both sectors combined.

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.

Attributes
ACN	1457729
Time
Date	201706
Local Time Of Day	0001-0600
Place
Locale Reference	S46.TRACON
State Reference	WA
Aircraft 1
Make Model Name	Medium Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 135
Flight Phase	Initial Climb
Route In Use	Vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Medium Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 121
Flight Phase	Initial Climb
Flight Plan	IFR
Person 1
Function	Departure
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 2.5
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Procedural Clearance Deviation - Track / Heading All Types Inflight Event / Encounter CFTT / CFIT

Seattle TRACON controller reported that while instructing; the sector became overloaded and aircraft where in minimum vectoring areas below the required altitudes.