S46 TRACON controller reported a departing aircraft failed to turn to an assigned heading after beca...

Attributes
ACN	1708191
Time
Date	201912
Local Time Of Day	0001-0600
Place
Locale Reference	S46.TRACON
State Reference	WA
Environment
Flight Conditions	IMC
Aircraft 1
Make Model Name	Small Aircraft High Wing 1 Eng Retractable Gear
Operating Under FAR Part	Part 91
Flight Phase	Initial Climb
Flight Plan	IFR
Aircraft 2
Make Model Name	Large Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Route In Use	Other Instrument Approach
Flight Plan	IFR
Person 1
Function	Departure
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Deviation - Track / Heading All Types

Narrative:

I was working departure east with very light traffic. I released aircraft X from bfi in IMC weather. Aircraft X called on his departure and was squawking the wrong code. I climbed aircraft X to 040 and issued the correct beacon code. Bfi called to coordinate the departure on the improper beacon code; which I answered to roger. Once I got off the line with bfi I immediately noticed that aircraft X appeared to be tracking on a ssw heading toward sea with aircraft descending on final. I issued an instruction to aircraft X to fly heading 130 immediately. I shouted across the room for final to watch aircraft X and that I'm turning him. I then instructed aircraft X to fly heading 090 immediately. Aircraft X came in close proximity to aircraft Y descending on final approach into sea who was by then already switched to sea tower. When the event was over; I asked aircraft X what happened with their turn; to which they responded that they were disoriented in the IMC. I asked aircraft X to report above the cloud layer; and after they did; I issued the statement.I'm really not sure what could have been done differently from an ATC perspective. I should have immediately contacted local control-west at sea after I gave the turn away from the airport to warn the controller talking to aircraft Y on final. My phraseology was also rushed and not standard.

Original NASA ASRS Text

Title: S46 TRACON Controller reported a departing aircraft failed to turn to an assigned heading after became disoriented in IMC; resulting in an airborne conflict with another aircraft.

Narrative: I was working Departure East with very light traffic. I released Aircraft X from BFI in IMC weather. Aircraft X called on his departure and was squawking the wrong code. I climbed Aircraft X to 040 and issued the correct beacon code. BFI called to coordinate the departure on the improper beacon code; which I answered to roger. Once I got off the line with BFI I immediately noticed that Aircraft X appeared to be tracking on a SSW heading toward SEA with aircraft descending on final. I issued an instruction to Aircraft X to fly heading 130 immediately. I shouted across the room for Final to watch Aircraft X and that I'm turning him. I then instructed Aircraft X to fly heading 090 immediately. Aircraft X came in close proximity to Aircraft Y descending on final approach into SEA who was by then already switched to SEA Tower. When the event was over; I asked Aircraft X what happened with their turn; to which they responded that they were disoriented in the IMC. I asked Aircraft X to report above the cloud layer; and after they did; I issued the statement.I'm really not sure what could have been done differently from an ATC perspective. I should have immediately contacted LC-W at SEA after I gave the turn away from the airport to warn the controller talking to Aircraft Y on final. My phraseology was also rushed and not standard.

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.

S46 TRACON controller reported a departing aircraft failed to turn to an assigned heading after became disoriented in IMC; resulting in an airborne conflict with another aircraft.