Near midair collision while conducting a visual approach.

Attributes
ACN	296319
Time
Date	199502
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : sea
State Reference	WA
Altitude	msl bound lower : 1800 msl bound upper : 1800
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sea
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 121
Flight Phase	descent : approach landing other
Route In Use	approach : visual arrival other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : approach landing other
Route In Use	approach : visual arrival other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Experience	flight time last 90 days : 300 flight time total : 6000
ASRS Report	296319
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : nmac other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : took evasive action none taken : unable
Consequence	Other
Miss Distance	horizontal : 300 vertical : 100
Supplementary
Primary Problem	ATC Human Performance

Narrative:

At seattle tacoma international airport, approach control placed us, via radar vectors, on left base to runway 16L. We were assigned 210 KTS at 5000 ft and 250 degree heading traffic for a visual approach was called to us. We did not have the traffic to follow but we searched for the md-80 and found him. By the time we found the traffic our assigned vector (250 degrees) had us perpendicular and abeam the extended centerline of runway 16L. So we are north of the airport heading west and began our visual. We approached final from right to left. Approach advised maintain 180 KTS to boeing field, and call tower. Just past boeing field on approach to runway 16L at sea I observed a TCASII alert. The TCASII showed plus 01 (100 ft) and the target was directly overhead. I added forward pressure to the yoke and searched for the target. Within seconds a B-737 appeared on my right approximately 200-300 ft. His speed was faster than ours. I watched his gear extend. The 737 was never in front of us, and never called as traffic to us. When the 'event' happened we were configured, on speed, and just past boeing field. We were on GS. The approach and landing after the event was normal. The captain and I debriefed the chief pilot.

Original NASA ASRS Text

Title: NMAC WHILE CONDUCTING A VISUAL APCH.

Narrative: AT SEATTLE TACOMA INTL ARPT, APCH CTL PLACED US, VIA RADAR VECTORS, ON L BASE TO RWY 16L. WE WERE ASSIGNED 210 KTS AT 5000 FT AND 250 DEG HDG TFC FOR A VISUAL APCH WAS CALLED TO US. WE DID NOT HAVE THE TFC TO FOLLOW BUT WE SEARCHED FOR THE MD-80 AND FOUND HIM. BY THE TIME WE FOUND THE TFC OUR ASSIGNED VECTOR (250 DEGS) HAD US PERPENDICULAR AND ABEAM THE EXTENDED CTRLINE OF RWY 16L. SO WE ARE N OF THE ARPT HDG W AND BEGAN OUR VISUAL. WE APCHED FINAL FROM R TO L. APCH ADVISED MAINTAIN 180 KTS TO BOEING FIELD, AND CALL TWR. JUST PAST BOEING FIELD ON APCH TO RWY 16L AT SEA I OBSERVED A TCASII ALERT. THE TCASII SHOWED PLUS 01 (100 FT) AND THE TARGET WAS DIRECTLY OVERHEAD. I ADDED FORWARD PRESSURE TO THE YOKE AND SEARCHED FOR THE TARGET. WITHIN SECONDS A B-737 APPEARED ON MY R APPROX 200-300 FT. HIS SPD WAS FASTER THAN OURS. I WATCHED HIS GEAR EXTEND. THE 737 WAS NEVER IN FRONT OF US, AND NEVER CALLED AS TFC TO US. WHEN THE 'EVENT' HAPPENED WE WERE CONFIGURED, ON SPD, AND JUST PAST BOEING FIELD. WE WERE ON GS. THE APCH AND LNDG AFTER THE EVENT WAS NORMAL. THE CAPT AND I DEBRIEFED THE CHIEF PLT.

Data retrieved from NASA's ASRS site as of July 2007 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.