Narrative:

I lost the transponder on a B737 shortly after the aircraft passed lla. Having seen a lost transponder that would come back after a couple of updates before; I waited one update for the transponder to come back. When it did not come back; I advised the pilot that I had lost his transponder; and asked him to reset or recycle his transponder. The pilot responded something to the effect that he was aware of the situation and asked me to tell him if I got it back. It was during this time; that he passed exactly one thousand feet from an E145 then another B737. I pulled up the primary targets and could see his primary target. I tried to get the tag to track with the primary target; however; since I had not yet updated the equipment suffix it would not track the primary target. I called another controller to ask if he knew what the correct suffix was; he did not. I attempted to find it by searching the 7110.65 but could not find it at that time. I asked a supervisor if there would be an issue with him flying the q-routes across the gulf of mexico without a transponder. It did not occur to me that the real issue was that he was no longer rvsm qualified. I handed off the track to the next sector (lev - 24) and did some coordination with them. I gave the B737 a frequency change to the next controller. I was then relieved for training. On the next sector; I searched again for the correct equipment suffix and finally found it. I quick looked lev to see if they had yet updated it. Upon seeing that they had not yet updated the equipment suffix I called them and advised them that I thought the correct equipment suffix for that aircraft was /Y. He told me they had been looking for it too. After I got off the line with them; I quick looked them again to see if it was now tracking properly and that is when I saw the neg-rvsm indicator around the altitude. I then realized that I may have lost separation with multiple aircraft since he was no longer rvsm approved. I simply forgot that if an aircraft loses his transponder; he is no longer rvsm approved. And; because I was uncertain of what the correct equipment suffix was; I did not change his equipment suffix. If I had known it; I would have entered it and had the neg-rvsm indicator to remind me that he was no longer rvsm approved and I would have taken appropriate action. Recommendation; a simple 'cheat sheet' with the equipment suffixes would have helped.

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Original NASA ASRS Text

Title: ZHU Controller described his/her failure to note the non-adherence to RVSM requirements when an air carrier's transponder failed; questioning the possibility of multiple separation violations.

Narrative: I lost the transponder on a B737 shortly after the aircraft passed LLA. Having seen a lost transponder that would come back after a couple of updates before; I waited one update for the transponder to come back. When it did not come back; I advised the pilot that I had lost his transponder; and asked him to reset or recycle his transponder. The pilot responded something to the effect that he was aware of the situation and asked me to tell him if I got it back. It was during this time; that he passed exactly one thousand feet from an E145 then another B737. I pulled up the primary targets and could see his primary target. I tried to get the tag to track with the primary target; however; since I had not yet updated the equipment suffix it would not track the primary target. I called another Controller to ask if he knew what the correct suffix was; he did not. I attempted to find it by searching the 7110.65 but could not find it at that time. I asked a Supervisor if there would be an issue with him flying the Q-routes across the Gulf of Mexico without a transponder. It did not occur to me that the real issue was that he was no longer RVSM qualified. I handed off the track to the next sector (LEV - 24) and did some coordination with them. I gave the B737 a frequency change to the next Controller. I was then relieved for training. On the next sector; I searched again for the correct equipment suffix and finally found it. I quick looked LEV to see if they had yet updated it. Upon seeing that they had not yet updated the equipment suffix I called them and advised them that I thought the correct equipment suffix for that aircraft was /Y. He told me they had been looking for it too. After I got off the line with them; I quick looked them again to see if it was now tracking properly and that is when I saw the Neg-RVSM indicator around the altitude. I then realized that I may have lost separation with multiple aircraft since he was no longer RVSM approved. I simply forgot that if an aircraft loses his transponder; he is no longer RVSM approved. And; because I was uncertain of what the correct equipment suffix was; I did not change his equipment suffix. If I had known it; I would have entered it and had the neg-RVSM indicator to remind me that he was no longer RVSM approved and I would have taken appropriate action. Recommendation; a simple 'cheat sheet' with the equipment suffixes would have helped.

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.