Narrative:

Runways 30L/30R were in use at sjc. I took a point out from lick sector on a VFR skyhawk 10-miles to the southeast of sjc; tracking northwest toward sjc with destination sql or pao airport. When the skyhawk was 2-3 miles east of sjc at 2;000 ft MSL; the aircraft was tracking in a direction that would place it over mid-field sjc airport; so as to not be a factor for jet aircraft departing runway 30R at sjc. The skyhawk was on an 'north' tag as it approached sjc; indicating that moffett (nuq) would soon be in control of the aircraft. At this time; a B737 was told about the VFR skyhawk at 2;000 ft; and that it would pass behind. The B737 was cleared for take off. After the B737 began its take off roll; the skyhawk was observed making a right turn; tracking northbound instead of continuing its previous track toward nuq as expected. I called nuq and asked if they were talking to the C172; to which they replied negative. At the time the B737 was lifting off runway 30R; the C172 was on the north side of the runway 30R departure corridor; tracking north at 2;000 ft MSL. I then told the B737 that the traffic was passing off their right side; no factor; and to contact norcal departure. I told the B737 that traffic was no factor based upon the radar track of the C172. After the B737 was switched to departure frequency; the radar track for the C172 immediately; and unexpectedly; began to turn toward my departure corridor; and toward the B737. I called toga sector; the sector who would be talking to the B737; to inquire about the C172 and advise them that I was not talking to the C172. Toga was not talking to the C172; nor was nuq when I called moffett back. Norcal later called sjc tower to let us know that the C172 was instructed to cross sjc midfield westbound; as I had expected. Norcal said that the pilot of the C172 may be issued a pilot deviation. The radar targets of the two aircraft did not merge; however the proximity of the C172 to the B737 may have caused alarm for the two pilots. When I accepted the C172 point out from norcal TRACON; I expected that the TRACON would keep the C172 clear of the departure corridor; because I had obtained releases for several jet aircraft which would fly through that protected corridor. I continued departures based on the fact that I had these releases and based on the track of the C172. The C172 made an immediate; unanticipated course change toward the B737; which was not evident on the radar when the B737 was changed to departure frequency. I will exercise additional vigilance when aircraft are operating near my departure corridor; and I will remember to factor in the possibility of unexpected pilot actions; especially when I am not in direct communication with them. When communicating 'traffic no factor' I will remember to take into consideration that a radar track is slightly delayed information and that slower aircraft can change course much more rapidly than faster aircraft.

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Original NASA ASRS Text

Title: SJC Controller described a conflict between a VFR point out from NCT and an IFR Air Carrier departure from Runway 30R; the VFR traffic apparently not complying with airport crossing instructions.

Narrative: Runways 30L/30R were in use at SJC. I took a point out from Lick Sector on a VFR Skyhawk 10-miles to the southeast of SJC; tracking northwest toward SJC with destination SQL or PAO airport. When the Skyhawk was 2-3 miles east of SJC at 2;000 FT MSL; the aircraft was tracking in a direction that would place it over mid-field SJC airport; so as to not be a factor for jet aircraft departing Runway 30R at SJC. The Skyhawk was on an 'N' tag as it approached SJC; indicating that Moffett (NUQ) would soon be in control of the aircraft. At this time; a B737 was told about the VFR Skyhawk at 2;000 FT; and that it would pass behind. The B737 was cleared for take off. After the B737 began its take off roll; the Skyhawk was observed making a right turn; tracking northbound instead of continuing its previous track toward NUQ as expected. I called NUQ and asked if they were talking to the C172; to which they replied negative. At the time the B737 was lifting off Runway 30R; the C172 was on the north side of the Runway 30R departure corridor; tracking north at 2;000 FT MSL. I then told the B737 that the traffic was passing off their right side; no factor; and to contact Norcal Departure. I told the B737 that traffic was no factor based upon the RADAR track of the C172. After the B737 was switched to Departure frequency; the RADAR track for the C172 immediately; and unexpectedly; began to turn toward my departure corridor; and toward the B737. I called Toga Sector; the sector who would be talking to the B737; to inquire about the C172 and advise them that I was not talking to the C172. Toga was not talking to the C172; nor was NUQ when I called Moffett back. Norcal later called SJC Tower to let us know that the C172 was instructed to cross SJC midfield westbound; as I had expected. Norcal said that the pilot of the C172 may be issued a pilot deviation. The RADAR targets of the two aircraft did not merge; however the proximity of the C172 to the B737 may have caused alarm for the two pilots. When I accepted the C172 point out from Norcal TRACON; I expected that the TRACON would keep the C172 clear of the departure corridor; because I had obtained releases for several jet aircraft which would fly through that protected corridor. I continued departures based on the fact that I had these releases and based on the track of the C172. The C172 made an immediate; unanticipated course change toward the B737; which was not evident on the RADAR when the B737 was changed to Departure frequency. I will exercise additional vigilance when aircraft are operating near my departure corridor; and I will remember to factor in the possibility of unexpected pilot actions; especially when I am not in direct communication with them. When communicating 'traffic no factor' I will remember to take into consideration that a RADAR track is slightly delayed information and that slower aircraft can change course much more rapidly than faster aircraft.

Data retrieved from NASA's ASRS site as of July 2013 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.