Air carrier turbojet makes evasive maneuver to avoid other S46 sequenced traffic for runway 34L.

Attributes
ACN	517289
Time
Date	200107
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : sea.airport
State Reference	WA
Altitude	msl single value : 5000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : s46.tracon artcc : zma.artcc
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 2 Turbojet Eng
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer only : 34l other
Flight Phase	descent : approach
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : s46.tracon
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 121
Flight Phase	other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : flight engineer pilot : commercial pilot : atp
Experience	flight time last 90 days : 230 flight time total : 15000 flight time type : 273
ASRS Report	517289
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	conflict : nmac non adherence : published procedure non adherence : required legal separation
Independent Detector	aircraft equipment : tcas other flight crewa
Resolutory Action	flight crew : took evasive action
Miss Distance	horizontal : 0 vertical : 200
Supplementary
Problem Areas	Environmental Factor Airspace Structure ATC Human Performance
Primary Problem	ATC Human Performance

Narrative:

We were being vectored for the mall visual approach into seattle. On base leg, approach gave us a right descending turn and reported traffic to our right and below as an air carrier X flight. We then had a hard TCASII warning to increase descent rate. First officer was flying and complied. I looked to my left and another aircraft (air carrier Y) was closing rapidly from 10 O'clock position. I shoved the nose over and pulled up the speed brakes to increase separation and we passed approximately 200 ft under that aircraft. Maneuver was hard and abrupt. There is no doubt in my mind had I not done it we would have collided.

Original NASA ASRS Text

Title: ACR TURBOJET MAKES EVASIVE MANEUVER TO AVOID OTHER S46 SEQUENCED TFC FOR RWY 34L.

Narrative: WE WERE BEING VECTORED FOR THE MALL VISUAL APCH INTO SEATTLE. ON BASE LEG, APCH GAVE US A R DSNDING TURN AND RPTED TFC TO OUR R AND BELOW AS AN ACR X FLT. WE THEN HAD A HARD TCASII WARNING TO INCREASE DSCNT RATE. FO WAS FLYING AND COMPLIED. I LOOKED TO MY L AND ANOTHER ACFT (ACR Y) WAS CLOSING RAPIDLY FROM 10 O'CLOCK POS. I SHOVED THE NOSE OVER AND PULLED UP THE SPD BRAKES TO INCREASE SEPARATION AND WE PASSED APPROX 200 FT UNDER THAT ACFT. MANEUVER WAS HARD AND ABRUPT. THERE IS NO DOUBT IN MY MIND HAD I NOT DONE IT WE WOULD HAVE COLLIDED.

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.