Narrative:

Our aircraft was in a VFR descent for the nantucket airport. Nantucket ATIS was reporting that runways 24 and 30 were in use for arrivals and runway 15 for VFR departures. Nantucket tower was also on dual control. At about 15 miles away from our arrival airport cape approach; who was giving us flight following; handed us off to the nantucket tower. Upon checking in with the first tower frequency; we were told to fly the northern shoreline for a right base entry for runway 24. We were also advised that we were to follow a piper malibu in to the airport by the nantucket tower. After acquiring the aircraft we were to follow for runway 24 I continued to finish checklists and set up the aircraft for our arrival in to the airport. At this point the pilot flying was scanning the area for traffic and then observed another aircraft at our 2 to 3 o'clock position about 30 - 50 ft off our right wing and no more than 100 ft below our current altitude. Seeing our aircraft was in a descent we were set for a collision course with the other aircraft. The pilot flying called traffic then started an abrupt climb to avoid the aircraft. After clearing the outbound traffic we reported the traffic to the tower. Tower reported that they did not have a transponder return from the aircraft. Therefore we never received a traffic call or a TCAS report from our aircraft. We also did not hear any communication with the aircraft. 1) nantucket tower did not advise of any conflicting traffic. 2) the aircraft either did not have transponder on or was not functioning properly. 3) departures off of runway 15 were being told to make right turn and fly overhead to the north to avoid IFR departing traffic on runway 24; but into VFR arrivals for runway 24.

Related reports:

Google
 

Original NASA ASRS Text

Title: A flight crew reported a near miss approach ACK with another aircraft which had departed but had no transponder and not talking to ATC.

Narrative: Our aircraft was in a VFR descent for the Nantucket airport. Nantucket ATIS was reporting that Runways 24 and 30 were in use for arrivals and Runway 15 for VFR departures. Nantucket Tower was also on dual control. At about 15 miles away from our arrival airport Cape Approach; who was giving us flight following; handed us off to the Nantucket Tower. Upon checking in with the first Tower frequency; we were told to fly the northern shoreline for a right base entry for Runway 24. We were also advised that we were to follow a Piper Malibu in to the airport by the Nantucket Tower. After acquiring the aircraft we were to follow for Runway 24 I continued to finish checklists and set up the aircraft for our arrival in to the airport. At this point the pilot flying was scanning the area for traffic and then observed another aircraft at our 2 to 3 o'clock position about 30 - 50 FT off our right wing and no more than 100 FT below our current altitude. Seeing our aircraft was in a descent we were set for a collision course with the other aircraft. The pilot flying called traffic then started an abrupt climb to avoid the aircraft. After clearing the outbound traffic we reported the traffic to the Tower. Tower reported that they did not have a transponder return from the aircraft. Therefore we never received a traffic call or a TCAS report from our aircraft. We also did not hear any communication with the aircraft. 1) Nantucket Tower did not advise of any conflicting traffic. 2) The aircraft either did not have transponder on or was not functioning properly. 3) Departures off of Runway 15 were being told to make right turn and fly overhead to the north to avoid IFR departing traffic on Runway 24; but into VFR arrivals for Runway 24.

Data retrieved from NASA's ASRS site as of April 2012 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.