An air carrier light transport has near midair collision with unknown small transport.

Attributes
ACN	122253
Time
Date	198908
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : vrb
State Reference	FL
Altitude	msl bound lower : 8000 msl bound upper : 8000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zma tower : psc
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Transport
Flight Phase	climbout : intermediate altitude
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 240 flight time total : 4100 flight time type : 1200
ASRS Report	122253
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	conflict : nmac
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	Other
Miss Distance	horizontal : 150 vertical : 150
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were straight and level, assigned heading 130 degree, assigned altitude 8000', en route mco-pbi via stoop intersection. Center had called other traffic to us, all low and no factor. As I was scanning left to right, an aircraft appeared suddenly at our 12:15 to 12:30 position climbing fairly rapidly through our altitude and with an estimated heading of 180-200 in a slight right bank, miss distance about 150'. I snapped in about 30 degree angle of bank and about 2 G's, by which time the collision course was broken and I rolled easily back to wings level. As we were very quickly passing through the other aircraft 6 O'clock, we couldn't observe any numbers or corporate markings. We did notice it was a white twin engine turboprop t-tail with blue and possibly some red trim. I made a near miss report with ATC, but they were unable to locate or identify the aircraft. I suspect he had been climbing up under me from my left 6:15, had a higher forward and vertical speed, and zoomed up under my nose unaware of my existence. I couldn't see him because of the fuselage and wings of my light transport. We were lucky.

Original NASA ASRS Text

Title: AN ACR LTT HAS NMAC WITH UNKNOWN SMT.

Narrative: WE WERE STRAIGHT AND LEVEL, ASSIGNED HDG 130 DEG, ASSIGNED ALT 8000', ENRTE MCO-PBI VIA STOOP INTXN. CENTER HAD CALLED OTHER TFC TO US, ALL LOW AND NO FACTOR. AS I WAS SCANNING LEFT TO RIGHT, AN ACFT APPEARED SUDDENLY AT OUR 12:15 TO 12:30 POSITION CLIMBING FAIRLY RAPIDLY THROUGH OUR ALT AND WITH AN ESTIMATED HDG OF 180-200 IN A SLIGHT RIGHT BANK, MISS DISTANCE ABOUT 150'. I SNAPPED IN ABOUT 30 DEG ANGLE OF BANK AND ABOUT 2 G'S, BY WHICH TIME THE COLLISION COURSE WAS BROKEN AND I ROLLED EASILY BACK TO WINGS LEVEL. AS WE WERE VERY QUICKLY PASSING THROUGH THE OTHER ACFT 6 O'CLOCK, WE COULDN'T OBSERVE ANY NUMBERS OR CORPORATE MARKINGS. WE DID NOTICE IT WAS A WHITE TWIN ENGINE TURBOPROP T-TAIL WITH BLUE AND POSSIBLY SOME RED TRIM. I MADE A NEAR MISS REPORT WITH ATC, BUT THEY WERE UNABLE TO LOCATE OR IDENTIFY THE ACFT. I SUSPECT HE HAD BEEN CLIMBING UP UNDER ME FROM MY LEFT 6:15, HAD A HIGHER FORWARD AND VERTICAL SPEED, AND ZOOMED UP UNDER MY NOSE UNAWARE OF MY EXISTENCE. I COULDN'T SEE HIM BECAUSE OF THE FUSELAGE AND WINGS OF MY LTT. WE WERE LUCKY.

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.