B757 mistook heading assignment for airspeed assignment. Approach controller missed incorrect readback. TCASII advisory results.

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Attributes
ACN	454310
Time
Date	199911
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : bfi.airport
State Reference	WA
Altitude	msl single value : 8000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : s46.tracon
Operator	general aviation : corporate
Make Model Name	B757-200
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	descent : approach descent : intermediate altitude
Route In Use	approach : instrument precision arrival : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : s46.tracon
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 60 flight time total : 8500 flight time type : 400
ASRS Report	454310
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial
Events
Anomaly	conflict : nmac non adherence : clearance non adherence : far other anomaly other spatial deviation
Independent Detector	atc equipment : conflict alert aircraft equipment : tcas other controllera other flight crewa
Resolutory Action	controller : issued advisory controller : issued new clearance none taken : detected after the fact
Miss Distance	horizontal : 6000 vertical : 400
Supplementary
Problem Areas	Environmental Factor Flight Crew Human Performance ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

During approach to boeing field, the controller cleared me to turn to a heading of 190 degrees (from 250 degrees). I thought he said slow to 190 KTS, which I repeated back to him. After a brief period, the controller asked my heading and I said 250 degrees. He replied that we were instructed to turn to 190 degrees. He then cleared me to a heading of 150 degrees and a descent. This turn/descent produced a TCASII advisory with conflicting traffic. We were then instructed to turn back to 250 degrees. The flight continued without further incident. There was a lot of radio traffic during the approach. The controller was talking rapidly to several aircraft. His workload appeared to be high -- as was ours. I was distraction at the moment the controller issued the heading change to 190 degrees and only heard the number 190 along with my call sign. I read back the airspeed change to 190 and assumed 'no response' meant my readback was correct.

Original NASA ASRS Text

Title: B757 MISTOOK HDG ASSIGNMENT FOR AIRSPD ASSIGNMENT. APCH CTLR MISSED INCORRECT READBACK. TCASII ADVISORY RESULTS.

Narrative: DURING APCH TO BOEING FIELD, THE CTLR CLRED ME TO TURN TO A HDG OF 190 DEGS (FROM 250 DEGS). I THOUGHT HE SAID SLOW TO 190 KTS, WHICH I REPEATED BACK TO HIM. AFTER A BRIEF PERIOD, THE CTLR ASKED MY HDG AND I SAID 250 DEGS. HE REPLIED THAT WE WERE INSTRUCTED TO TURN TO 190 DEGS. HE THEN CLRED ME TO A HDG OF 150 DEGS AND A DSCNT. THIS TURN/DSCNT PRODUCED A TCASII ADVISORY WITH CONFLICTING TFC. WE WERE THEN INSTRUCTED TO TURN BACK TO 250 DEGS. THE FLT CONTINUED WITHOUT FURTHER INCIDENT. THERE WAS A LOT OF RADIO TFC DURING THE APCH. THE CTLR WAS TALKING RAPIDLY TO SEVERAL ACFT. HIS WORKLOAD APPEARED TO BE HIGH -- AS WAS OURS. I WAS DISTR AT THE MOMENT THE CTLR ISSUED THE HDG CHANGE TO 190 DEGS AND ONLY HEARD THE NUMBER 190 ALONG WITH MY CALL SIGN. I READ BACK THE AIRSPD CHANGE TO 190 AND ASSUMED 'NO RESPONSE' MEANT MY READBACK WAS CORRECT.

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.