Narrative:

VFR flight to execute practice ILS approaches to evaluate new avionics installation on aircraft. Passenger in the right seat was a rated and current pilot. We specifically wished to use the autopilot to shoot the ILS approach using the GNS-430W navigation radio and the EFIS installed on the right side and ensure the autopilot coupling worked correctly. Departed VFR and requested flight following from TRACON and asked for vectors for a practice ILS. TRACON assigned us a squawk code and advised radar contact. TRACON asked what we wanted to do after we completed the ILS and I responded we would like to go around for another ILS. TRACON assigned a southerly heading and 2;000 ft. At about this time; TRACON advised that the airport had gone IFR with a 700 ft ceiling and asked our intentions. I stated that we would like an IFR clearance from our present position utilizing the ILS and would terminate in a full stop at the practice airport. Our call sign was nxab and there was another aircraft with a call sign that ended in xac. This aircraft answered calls meant for us several times. Additionally the controller was referring to us as 'seminole' xab. I responded to these calls and eventually mentioned to the controller our aircraft type. During this time the controller issued heading changes and the other aircraft continued to respond to calls to our tail number; resulting in more confusion for us and the controller. I heard the controller issue an instruction to climb to 3;000 ft but was not sure which aircraft the instruction was for. However; the other aircraft responded and the controller did not say anything further. Finally; the controller told the other aircraft that they were answering calls meant for us. The controller then gave the other aircraft a heading change with some urgency in her voice. The other aircraft seemed to be slow in responding. The controller then instructed me to immediately turn right to heading 270 and climb and maintain 3;000 ft. I noted her urgency in her voice and immediately disconnected the autopilot and made a steep climbing turn to heading 270 and 3;000 ft. The controller asked me if I had the traffic in sight. I did not; but told her that I had seen them on the tis traffic screen installed in my aircraft. We were then vectored to the ILS and landed uneventfully at practice airport. The local controller at the practice airport told me that TRACON wanted me to call them on the phone. I called TRACON and the person I talked to asked me about the incident and wanted to make sure that I was answering calls to xab even though the controller was referring to us as a different kind of aircraft. I assured him that I was doing so; but that the situation was confusing. I discussed the situation with the other pilot flying with me and he concurred that he had not heard an instruction for us to climb to 3;000 ft. I think it is possible that the controller might have used the wrong tail number when issuing the climb instruction. This kind of communications failure must always be guarded against by pilots and controllers. Considering the obvious with tail numbers and ATC instructions; I wish I had spoken up immediately when I suspected the other aircraft was responding to calls meant for us; I also wish I had queried the controller concerning who was supposed to be climbing to 3;000 ft.

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Original NASA ASRS Text

Title: A Pilot and a Controller described the communication confusion as two similar call sign aircraft practiced ILS's in IMC conditions at the same airport.

Narrative: VFR flight to execute practice ILS approaches to evaluate new avionics installation on aircraft. Passenger in the right seat was a rated and current pilot. We specifically wished to use the autopilot to shoot the ILS approach using the GNS-430W NAV radio and the EFIS installed on the right side and ensure the autopilot coupling worked correctly. Departed VFR and requested flight following from TRACON and asked for vectors for a practice ILS. TRACON assigned us a squawk code and advised radar contact. TRACON asked what we wanted to do after we completed the ILS and I responded we would like to go around for another ILS. TRACON assigned a southerly heading and 2;000 FT. At about this time; TRACON advised that the airport had gone IFR with a 700 FT ceiling and asked our intentions. I stated that we would like an IFR clearance from our present position utilizing the ILS and would terminate in a full stop at the practice airport. Our call sign was NxAB and there was another aircraft with a call sign that ended in xAC. This aircraft answered calls meant for us several times. Additionally the Controller was referring to us as 'Seminole' xAB. I responded to these calls and eventually mentioned to the Controller our aircraft type. During this time the Controller issued heading changes and the other aircraft continued to respond to calls to our tail number; resulting in more confusion for us and the Controller. I heard the Controller issue an instruction to climb to 3;000 FT but was not sure which aircraft the instruction was for. However; the other aircraft responded and the Controller did not say anything further. Finally; the Controller told the other aircraft that they were answering calls meant for us. The Controller then gave the other aircraft a heading change with some urgency in her voice. The other aircraft seemed to be slow in responding. The Controller then instructed me to immediately turn right to heading 270 and climb and maintain 3;000 FT. I noted her urgency in her voice and immediately disconnected the autopilot and made a steep climbing turn to heading 270 and 3;000 FT. The Controller asked me if I had the traffic in sight. I did not; but told her that I had seen them on the TIS Traffic Screen installed in my aircraft. We were then vectored to the ILS and landed uneventfully at practice airport. The Local Controller at the practice airport told me that TRACON wanted me to call them on the phone. I called TRACON and the person I talked to asked me about the incident and wanted to make sure that I was answering calls to xAB even though the Controller was referring to us as a different kind of aircraft. I assured him that I was doing so; but that the situation was confusing. I discussed the situation with the other pilot flying with me and he concurred that he had not heard an instruction for us to climb to 3;000 FT. I think it is possible that the Controller might have used the wrong tail number when issuing the climb instruction. This kind of communications failure must always be guarded against by pilots and Controllers. Considering the obvious with tail numbers and ATC instructions; I wish I had spoken up immediately when I suspected the other aircraft was responding to calls meant for us; I also wish I had queried the Controller concerning who was supposed to be climbing to 3;000 FT.

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.