IFR C340 pilot experiences near midair collision with uncontrolled cessna single.

Attributes
ACN	720357
Time
Date	200612
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : x06.airport
State Reference	FL
Altitude	msl single value : 3000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : tpa.tracon
Operator	general aviation : corporate
Make Model Name	Cessna 340/340A
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Make Model Name	Cessna Single Piston Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Person 1
Affiliation	company : corporate
Function	flight crew : single pilot
Qualification	pilot : multi engine pilot : instrument pilot : cfi pilot : atp
Experience	flight time last 90 days : 175 flight time total : 2500 flight time type : 200
ASRS Report	720357
Person 2
Function	flight crew : single pilot
Events
Independent Detector	other controllera
Resolutory Action	controller : issued alert flight crew : took evasive action
Miss Distance	horizontal : 250 vertical : 50
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance Airspace Structure
Primary Problem	Ambiguous

Narrative:

Had just leveled off at assigned altitude; when ATC (tampa approach) called traffic was on my right; wbound. Had no joy on the traffic. ATC then informed me traffic was or had passed beneath me; and was no factor. Short while later; ATC called again that traffic had changed direction; wbound now at approximately 11 O'clock position. Just then I saw the single engine aircraft on a converging course appeared to be at the same altitude. I told tampa approach I was going to climb; and simultaneously initiated a climb to about +200 ft. I passed over the traffic; and returned to assigned altitude. ATC apologized for not calling it sooner. I wished I'd have seen it sooner. I'm usually constantly vigilant about scanning for traffic even on IFR in VMC. This one just escaped my scan. Yikes.

Original NASA ASRS Text

Title: IFR C340 PLT EXPERIENCES NMAC WITH UNCTLED CESSNA SINGLE.

Narrative: HAD JUST LEVELED OFF AT ASSIGNED ALT; WHEN ATC (TAMPA APCH) CALLED TFC WAS ON MY R; WBOUND. HAD NO JOY ON THE TFC. ATC THEN INFORMED ME TFC WAS OR HAD PASSED BENEATH ME; AND WAS NO FACTOR. SHORT WHILE LATER; ATC CALLED AGAIN THAT TFC HAD CHANGED DIRECTION; WBOUND NOW AT APPROX 11 O'CLOCK POS. JUST THEN I SAW THE SINGLE ENG ACFT ON A CONVERGING COURSE APPEARED TO BE AT THE SAME ALT. I TOLD TAMPA APCH I WAS GOING TO CLB; AND SIMULTANEOUSLY INITIATED A CLB TO ABOUT +200 FT. I PASSED OVER THE TFC; AND RETURNED TO ASSIGNED ALT. ATC APOLOGIZED FOR NOT CALLING IT SOONER. I WISHED I'D HAVE SEEN IT SOONER. I'M USUALLY CONSTANTLY VIGILANT ABOUT SCANNING FOR TFC EVEN ON IFR IN VMC. THIS ONE JUST ESCAPED MY SCAN. YIKES.

Data retrieved from NASA's ASRS site as of January 2009 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.