A lax tower controller was charged with having a separation error with parallel runway departures. T...

Attributes
ACN	1405485
Time
Date	201611
Local Time Of Day	0001-0600
Place
Locale Reference	LAX.Airport
State Reference	CA
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	Caravan Undifferentiated
Operating Under FAR Part	Part 121
Flight Phase	Initial Climb
Route In Use	Vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	Initial Climb
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Local Coordinator
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 13
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Procedural Clearance Deviation - Track / Heading All Types

Narrative:

I was working local assist 2 for the local controller and had no role in the event. I was shown the falcon [radar data replay program] replay and do not believe tower had an error. Aircraft X had departed and was issued a 271 heading to obtain 15 degrees divergence. Aircraft Y departed the parallel runway and was on the SID which tracks 256 degrees. On the falcon there was one sweep that showed aircraft Y's change of heading to the right approximately 20 degrees and then the next sweep back to his original track. It is physically impossible for that aircraft to make that heading change. That appears to be a failure in the falcon software. Then [later;] there appears to be another loss of 15 degrees. At that time aircraft X's track turns left approximately 10 degrees. If sct didn't turn that aircraft left; then it should be a pilot deviation for not maintaining heading.I believe lax tower did everything correct.

Original NASA ASRS Text

Title: A LAX Tower Controller was charged with having a separation error with parallel runway departures. The Assist Controller believed the 15 degree divergence rule was applied correctly.

Narrative: I was working Local Assist 2 for the Local Controller and had no role in the event. I was shown the Falcon [Radar data replay program] replay and do not believe Tower had an error. Aircraft X had departed and was issued a 271 heading to obtain 15 degrees divergence. Aircraft Y departed the parallel runway and was on the SID which tracks 256 degrees. On the Falcon there was one sweep that showed Aircraft Y's change of heading to the right approximately 20 degrees and then the next sweep back to his original track. It is physically impossible for that aircraft to make that heading change. That appears to be a failure in the Falcon software. Then [later;] there appears to be another loss of 15 degrees. At that time Aircraft X's track turns left approximately 10 degrees. If SCT didn't turn that aircraft left; then it should be a pilot deviation for not maintaining heading.I believe LAX tower did everything correct.

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.

A lax tower controller was charged with having a separation error with parallel runway departures. The assist controller believed the 15 degree divergence rule was applied correctly.