T75 controller described an unsafe event when a stl air carrier initiated a wrong turn conflicting w...

Narrative:

A B737 was expecting visual approach 12L; weather in the area caused wind shift after they checked on. They were told to expect 30R; but to continue to the 12L downwind fix; shaad; previously assigned. This was due to opposite direction departure traffic that needed to pass before the B737 could turn toward the 30R final. I turned my attention to other aircraft; coordinating the runway change and a position relief briefing; and then noticed the B737 had turned toward toy; flying the STAR transition to 30R instead of continuing to shaad. This put them in unnecessary proximity to the opposite direction departure at a similar altitude; although the B737 was passing behind the traffic. It created an unsafe situation and separation was not ensured. This is another case of a controller being burned by autopilot; and not the first time I have experienced it. From talking to the crew; they explained that entering the new runway caused the aircraft to fly the 30R transition instead of continuing on the 12L transition as instructed. Would suggest crews do what it takes to follow ATC instructions; even if it means they delay entering the new runway in their system.

Original NASA ASRS Text

Title: T75 Controller described an unsafe event when a STL air carrier initiated a wrong turn conflicting with opposite direction traffic; the controller indicating that a premature autopilot change caused the occurrence.

Narrative: A B737 was expecting Visual Approach 12L; weather in the area caused wind shift after they checked on. They were told to expect 30R; but to continue to the 12L downwind fix; SHAAD; previously assigned. This was due to opposite direction departure traffic that needed to pass before the B737 could turn toward the 30R final. I turned my attention to other aircraft; coordinating the runway change and a position relief briefing; and then noticed the B737 had turned toward TOY; flying the STAR transition to 30R instead of continuing to SHAAD. This put them in unnecessary proximity to the opposite direction departure at a similar altitude; although the B737 was passing behind the traffic. It created an unsafe situation and separation was not ensured. This is another case of a controller being burned by autopilot; and not the first time I have experienced it. From talking to the crew; they explained that entering the new runway caused the aircraft to fly the 30R transition instead of continuing on the 12L transition as instructed. Would suggest crews do what it takes to follow ATC instructions; even if it means they delay entering the new runway in their system.

Data retrieved from NASA's ASRS site as of July 2013 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	1022525
Time
Date	201207
Local Time Of Day	0001-0600
Place
Locale Reference	STL.Airport
State Reference	MO
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR VANDALIA
Flight Plan	IFR
Person 1
Function	Approach Departure
Qualification	Air Traffic Control Fully Certified
Person 2
Function	Pilot Flying First Officer
Experience	Flight Crew Last 90 Days 200
Events
Anomaly	Deviation - Procedural Clearance Deviation - Track / Heading All Types

T75 controller described an unsafe event when a stl air carrier initiated a wrong turn conflicting with opposite direction traffic; the controller indicating that a premature autopilot change caused the occurrence.