Narrative:

The route of flight is as in the LOA with ack ATCT. This clearance means (flight identify) is cleared to the hyannis airport; via radar vectors direct hya. Upon establishing communication with cape approach; you may expect; 'vectors to join the marconi (lfv) 200 degree radial.' we departed nantucket runway 24 for hya; IFR. On the runway heading; climbing turn to 270 degrees; contact cape departure. Cape departure issued a right turn to 030 degrees and intercept to lfv 200 degree radial; climb to 3000 ft. Approximately 5 mins into the flight; cape approach issued a traffic alert! 'Traffic at 12 O'clock position; your altitude; traffic alert; immediate turn to 090 degrees!' making an immediate turn; I observed the traffic off my right wing; approximately 100-150 ft vertically and 300-350 ft horizontally in the opposite direction. Way too close for IFR operation under radar control. The traffic was a freight operation aircraft. The initial conversation with the freighter aircraft and approach was; approach: 'are you on the radial?' aircraft: 'no! Showing to the left pause; no to the right of course; correcting.' approach now thinking that aircraft would intercept the radial from the right side; giving the aircraft a change in sector frequencys. The pilot was confused on which way to turn to intercept the radial; and the situation got worse when the other aircraft continued to turn 180 degrees. Turning back at me while I was starting the turn and now turning into the aircraft and ATC did not have a good picture on what was going to occur; and it's a good chance that operational position training was in progress at the TRACON providing the radar service at that time.

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Original NASA ASRS Text

Title: PA31 WITH K90 EXPERIENCED CONFLICT WITH C402 ON DEP FROM ACK.

Narrative: THE RTE OF FLT IS AS IN THE LOA WITH ACK ATCT. THIS CLRNC MEANS (FLT IDENT) IS CLRED TO THE HYANNIS ARPT; VIA RADAR VECTORS DIRECT HYA. UPON ESTABLISHING COM WITH CAPE APCH; YOU MAY EXPECT; 'VECTORS TO JOIN THE MARCONI (LFV) 200 DEG RADIAL.' WE DEPARTED NANTUCKET RWY 24 FOR HYA; IFR. ON THE RWY HDG; CLBING TURN TO 270 DEGS; CONTACT CAPE DEP. CAPE DEP ISSUED A R TURN TO 030 DEGS AND INTERCEPT TO LFV 200 DEG RADIAL; CLB TO 3000 FT. APPROX 5 MINS INTO THE FLT; CAPE APCH ISSUED A TFC ALERT! 'TFC AT 12 O'CLOCK POS; YOUR ALT; TFC ALERT; IMMEDIATE TURN TO 090 DEGS!' MAKING AN IMMEDIATE TURN; I OBSERVED THE TFC OFF MY R WING; APPROX 100-150 FT VERTICALLY AND 300-350 FT HORIZONTALLY IN THE OPPOSITE DIRECTION. WAY TOO CLOSE FOR IFR OP UNDER RADAR CTL. THE TFC WAS A FREIGHT OP ACFT. THE INITIAL CONVERSATION WITH THE FREIGHTER ACFT AND APCH WAS; APCH: 'ARE YOU ON THE RADIAL?' ACFT: 'NO! SHOWING TO THE L PAUSE; NO TO THE R OF COURSE; CORRECTING.' APCH NOW THINKING THAT ACFT WOULD INTERCEPT THE RADIAL FROM THE R SIDE; GIVING THE ACFT A CHANGE IN SECTOR FREQS. THE PLT WAS CONFUSED ON WHICH WAY TO TURN TO INTERCEPT THE RADIAL; AND THE SIT GOT WORSE WHEN THE OTHER ACFT CONTINUED TO TURN 180 DEGS. TURNING BACK AT ME WHILE I WAS STARTING THE TURN AND NOW TURNING INTO THE ACFT AND ATC DID NOT HAVE A GOOD PICTURE ON WHAT WAS GOING TO OCCUR; AND IT'S A GOOD CHANCE THAT OPERATIONAL POS TRAINING WAS IN PROGRESS AT THE TRACON PROVIDING THE RADAR SVC AT THAT TIME.

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.