Reduced speed assigned without advising approach controller.

Attributes
ACN	94802
Time
Date	198809
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : ord
State Reference	IL
Altitude	msl bound lower : 10000 msl bound upper : 10000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zau tracon : ord
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute : on vectors enroute airway : ord
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : flight engineer pilot : commercial
Experience	flight time last 90 days : 150 flight time total : 10000 flight time type : 7300
ASRS Report	94802
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : commercial pilot : atp
Experience	flight time last 90 days : 210 flight time total : 13000 flight time type : 8000
ASRS Report	94801
Events
Anomaly	conflict : airborne less severe non adherence : clearance other anomaly
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 24000
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Approaching ord, ZID assigned 320 KTS airspeed for the descent. ZAU asked our indicated airspeed and made no comment. On reaching 10000' MSL and a point about 10 mi from ord I initiated a speed reduction to 250 KTS in anticipation of a rapid descent. At reaching 250 KTS ord approach queried our airspeed and why we had reduced, ie, had anyone given us the reduction. We replied in the negative. We were then told to expedite to 9000' MSL and advised of traffic closing behind 'at 4 NM.' prior experience at this airport led me to think our assigned airspeed had been overlooked by ord approach and that, as close to the airport as we were, a descent clearance was imminent. It was a false assumption on my part as the PF. The obvious solution, in retrospect, would have been to verify if the (high) airspeed were still needed by the controller.

Original NASA ASRS Text

Title: REDUCED SPEED ASSIGNED WITHOUT ADVISING APCH CTLR.

Narrative: APCHING ORD, ZID ASSIGNED 320 KTS AIRSPD FOR THE DSCNT. ZAU ASKED OUR INDICATED AIRSPD AND MADE NO COMMENT. ON REACHING 10000' MSL AND A POINT ABOUT 10 MI FROM ORD I INITIATED A SPD REDUCTION TO 250 KTS IN ANTICIPATION OF A RAPID DSCNT. AT REACHING 250 KTS ORD APCH QUERIED OUR AIRSPD AND WHY WE HAD REDUCED, IE, HAD ANYONE GIVEN US THE REDUCTION. WE REPLIED IN THE NEGATIVE. WE WERE THEN TOLD TO EXPEDITE TO 9000' MSL AND ADVISED OF TFC CLOSING BEHIND 'AT 4 NM.' PRIOR EXPERIENCE AT THIS ARPT LED ME TO THINK OUR ASSIGNED AIRSPD HAD BEEN OVERLOOKED BY ORD APCH AND THAT, AS CLOSE TO THE ARPT AS WE WERE, A DSCNT CLRNC WAS IMMINENT. IT WAS A FALSE ASSUMPTION ON MY PART AS THE PF. THE OBVIOUS SOLUTION, IN RETROSPECT, WOULD HAVE BEEN TO VERIFY IF THE (HIGH) AIRSPD WERE STILL NEEDED BY THE CTLR.

Data retrieved from NASA's ASRS site as of August 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.