C501 bizjet slowed below assigned airspeed on approach.

Attributes
ACN	421583
Time
Date	199812
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dtw
State Reference	MI
Altitude	msl bound lower : 4000 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Operator	general aviation : corporate
Route In Use	approach : visual arrival other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 150 flight time total : 10300 flight time type : 1000
ASRS Report	421583
Person 2
Affiliation	Other
Function	flight crew : first officer
Qualification	pilot : commercial
Events
Anomaly	non adherence : clearance non adherence : far
Independent Detector	other controllera
Consequence	Other
Supplementary
Air Traffic Incident	Pilot Deviation

Narrative:

On dec/xa/98 during vectors to a visual approach at dtw we were assigned a heading of 040 degrees and a speed of 180 KTS for in trail spacing. After a few mi on this heading, we were given a new heading of 090 degrees momentarily, and then a heading of 120 degrees, and then report visual contact of a DC9 on final for runway 21L at dtw. We confirmed visual contact of that aircraft. We were then told to follow the DC9 to runway 21L at dtw. After turning final behind the DC9, I felt that the spacing was a little too close as we were feeling his wake turbulence. Consequently, I slowed my speed by about 20 KTS. After a couple of mins the controller asked our speed, which my copilot replied, 'we are indicating 160 KTS.' the controller then replied for us to indicate 180 KTS. Then I replied, 'I had to slow for aircraft we are following.' controller replied, 'spacing is good, you have DC9 traffic behind you.' I then went back to 180 KTS until short final. This was the extent of the incident. Traffic maintained normal flow following this deviation.

Original NASA ASRS Text

Title: C501 BIZJET SLOWED BELOW ASSIGNED AIRSPD ON APCH.

Narrative: ON DEC/XA/98 DURING VECTORS TO A VISUAL APCH AT DTW WE WERE ASSIGNED A HDG OF 040 DEGS AND A SPD OF 180 KTS FOR IN TRAIL SPACING. AFTER A FEW MI ON THIS HDG, WE WERE GIVEN A NEW HDG OF 090 DEGS MOMENTARILY, AND THEN A HDG OF 120 DEGS, AND THEN RPT VISUAL CONTACT OF A DC9 ON FINAL FOR RWY 21L AT DTW. WE CONFIRMED VISUAL CONTACT OF THAT ACFT. WE WERE THEN TOLD TO FOLLOW THE DC9 TO RWY 21L AT DTW. AFTER TURNING FINAL BEHIND THE DC9, I FELT THAT THE SPACING WAS A LITTLE TOO CLOSE AS WE WERE FEELING HIS WAKE TURB. CONSEQUENTLY, I SLOWED MY SPD BY ABOUT 20 KTS. AFTER A COUPLE OF MINS THE CTLR ASKED OUR SPD, WHICH MY COPLT REPLIED, 'WE ARE INDICATING 160 KTS.' THE CTLR THEN REPLIED FOR US TO INDICATE 180 KTS. THEN I REPLIED, 'I HAD TO SLOW FOR ACFT WE ARE FOLLOWING.' CTLR REPLIED, 'SPACING IS GOOD, YOU HAVE DC9 TFC BEHIND YOU.' I THEN WENT BACK TO 180 KTS UNTIL SHORT FINAL. THIS WAS THE EXTENT OF THE INCIDENT. TFC MAINTAINED NORMAL FLOW FOLLOWING THIS DEV.

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.