C560 at 8000 ft with rdu TRACON experienced delay vectors because of unrpted speed reduction.

Attributes
ACN	613370
Time
Date	200403
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : rdu.airport
State Reference	NC
Altitude	msl single value : 8000
Environment
Flight Conditions	Mixed
Weather Elements	Rain Turbulence
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : rdu.tracon
Operator	general aviation : corporate
Make Model Name	Citation V
Operating Under FAR Part	Part 91
Flight Phase	descent : intermediate altitude
Route In Use	arrival : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : rdu.tracon
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 55 flight time total : 6000 flight time type : 2000
ASRS Report	613370
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Events
Anomaly	conflict : airborne less severe inflight encounter : turbulence inflight encounter : weather non adherence : published procedure non adherence : required legal separation other anomaly
Independent Detector	other flight crewa
Resolutory Action	controller : separated traffic controller : issued new clearance
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 17000 vertical : 991
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Ambiguous

Narrative:

We were flying a vector at 9000 ft as cleared. We were never assigned an airspeed, but flew at 250 KIAS. About 25 mi from rdu we were given a clearance to maintain 8000 ft. About that time we encountered light rain and moderate turbulence on an intermittent basis. We reduced our speed to about 220 KTS. After a few mins we were expecting a turn south for descent and downwind for our approach. The approach controller asked our speed. I replied '215 KTS.' he gave us a heading to the south and told us to maintain our current speed. I then called the controller sand said that I realized that I should have told him about our speed change. He replied 'yes, especially since we had traffic 3 mi in trail.' the rest of the flight was uneventful. As far as I am aware, no evasive action was taken by the following airplane. In hindsight, I realize that at the time that we reduced speed we were distraction by WX and changing planned instrument approachs, set up briefing, and xfer of controls. In addition, while I realize that it is my responsibility to inform ATC of speed changes, it would have been helpful to know that there was an airplane close in trail in IMC and to keep the speed up. I know that it is not an ATC requirement, but I have had most controllers warn or heads up a situation like this in the past. (Ie, 'you have an xyz 3 mi in trail, advise of speed reduction' or 'keep the speed up.') we were only about 12-15 NM from the airport when this situation occurred.

Original NASA ASRS Text

Title: C560 AT 8000 FT WITH RDU TRACON EXPERIENCED DELAY VECTORS BECAUSE OF UNRPTED SPD REDUCTION.

Narrative: WE WERE FLYING A VECTOR AT 9000 FT AS CLRED. WE WERE NEVER ASSIGNED AN AIRSPD, BUT FLEW AT 250 KIAS. ABOUT 25 MI FROM RDU WE WERE GIVEN A CLRNC TO MAINTAIN 8000 FT. ABOUT THAT TIME WE ENCOUNTERED LIGHT RAIN AND MODERATE TURB ON AN INTERMITTENT BASIS. WE REDUCED OUR SPD TO ABOUT 220 KTS. AFTER A FEW MINS WE WERE EXPECTING A TURN S FOR DSCNT AND DOWNWIND FOR OUR APCH. THE APCH CTLR ASKED OUR SPD. I REPLIED '215 KTS.' HE GAVE US A HDG TO THE S AND TOLD US TO MAINTAIN OUR CURRENT SPD. I THEN CALLED THE CTLR SAND SAID THAT I REALIZED THAT I SHOULD HAVE TOLD HIM ABOUT OUR SPD CHANGE. HE REPLIED 'YES, ESPECIALLY SINCE WE HAD TFC 3 MI IN TRAIL.' THE REST OF THE FLT WAS UNEVENTFUL. AS FAR AS I AM AWARE, NO EVASIVE ACTION WAS TAKEN BY THE FOLLOWING AIRPLANE. IN HINDSIGHT, I REALIZE THAT AT THE TIME THAT WE REDUCED SPD WE WERE DISTR BY WX AND CHANGING PLANNED INST APCHS, SET UP BRIEFING, AND XFER OF CTLS. IN ADDITION, WHILE I REALIZE THAT IT IS MY RESPONSIBILITY TO INFORM ATC OF SPD CHANGES, IT WOULD HAVE BEEN HELPFUL TO KNOW THAT THERE WAS AN AIRPLANE CLOSE IN TRAIL IN IMC AND TO KEEP THE SPD UP. I KNOW THAT IT IS NOT AN ATC REQUIREMENT, BUT I HAVE HAD MOST CTLRS WARN OR HEADS UP A SIT LIKE THIS IN THE PAST. (IE, 'YOU HAVE AN XYZ 3 MI IN TRAIL, ADVISE OF SPD REDUCTION' OR 'KEEP THE SPD UP.') WE WERE ONLY ABOUT 12-15 NM FROM THE ARPT WHEN THIS SIT OCCURRED.

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.