Narrative:

I left on an IFR flight plan enroute to ZZZ. Somewhere along the way I was ask to cut off the mode C because the altitude was not being reported correctly. I arrived at ZZZ departed shortly thereafter enroute to rsn. I had use about 1.3 hours of fuel. Btr departure again asked me to turn off the mode C for the same reason as before. Shortly thereafter the radios blinked a few times on and off and then began working normally. Btr turned me over to polk approach. They told me I was not in radar contact; cleared direct rsn come to aex VOR direct rsn. Being I could not go direct rsn and aex VOR at the same time; I asked if they wanted me to go direct aex and then rsn. He said that is correct. Knowing I could not do that and be legal with the fuel reserve when I arrived at rsn; I told them I will cancel IFR and go VFR. I heard a reply; but I could not understand what was being said because the radios began to blink on and off again about this time. My worst mistake would have been assuming it was my cancellation and could not confirm that being I was having radio problems. I turned the transponder to 1200 and climbed to 4500. Sometimes after the mode C has been off a while it will report correctly. The number 1 radio was left on the polk approach frequency until we were arriving at rsn. The number two radio was left to 122.8 and both were being monitored. I heard no additional transmissions. The radio blinked on and off a lot. I did try to contact rsn FBO on the number 2 radio and could not hear them because it was very muffled. I arrived at rsn. I had a message to call polk approach supervisor. I called him immediately. He told me they never received my cancellation request and they had to block off 4000 feet all they way to rsn because they did not know where I was at. He said no one could get down and I made them work three times as hard and had inconvenienced many people. He verified the conversation about the clearance. He said they never heard me cancel and did not see me on radar. He told me I was still on an IFR flight plan till they acknowledged my cancellation. I am aware of that and thought it had been received when the reply that I could hardly understand was received immediately after I had cancelled. He said they had tried to reach me and other aircraft had tried as well. The only way that would have been possible is if the radios were on the blink when I cancelled. They should have saw a VFR target at 4500 (3500 since it 1000? Off sometimes). I told him about my radio issue. He told me he would review the tapes again. However; I can not help what goes wrong enroute. At rsn I made sure the external screws on the wires connected to the voltage regulator were tight. I did let them know I had been having radio problems previously and if I did not talk to them I had lost my radios.

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Original NASA ASRS Text

Title: IFR general aviation aircraft experiencing radio and Mode C failures failed to properly relay cancellation of IFR status to ATC causing confusion as to aircraft location and delaying IFR service to other aircraft.

Narrative: I left on an IFR flight plan enroute to ZZZ. Somewhere along the way I was ask to cut off the Mode C because the altitude was not being reported correctly. I arrived at ZZZ departed shortly thereafter enroute to RSN. I had use about 1.3 hours of fuel. BTR departure again asked me to turn off the Mode C for the same reason as before. Shortly thereafter the radios blinked a few times on and off and then began working normally. BTR turned me over to Polk approach. They told me I was not in radar contact; cleared direct RSN come to AEX VOR direct RSN. Being I could not go direct RSN and AEX VOR at the same time; I asked if they wanted me to go direct AEX and then RSN. He said that is correct. Knowing I could not do that and be legal with the fuel reserve when I arrived at RSN; I told them I will cancel IFR and go VFR. I heard a reply; but I could not understand what was being said because the radios began to blink on and off again about this time. My worst mistake would have been assuming it was my cancellation and could not confirm that being I was having radio problems. I turned the transponder to 1200 and climbed to 4500. Sometimes after the Mode C has been off a while it will report correctly. The number 1 radio was left on the Polk approach frequency until we were arriving at RSN. The number two radio was left to 122.8 and both were being monitored. I heard no additional transmissions. The radio blinked on and off a lot. I did try to contact RSN FBO on the number 2 radio and could not hear them because it was very muffled. I arrived at RSN. I had a message to call Polk Approach Supervisor. I called him immediately. He told me they never received my cancellation request and they had to block off 4000 feet all they way to RSN because they did not know where I was at. He said no one could get down and I made them work three times as hard and had inconvenienced many people. He verified the conversation about the clearance. He said they never heard me cancel and did not see me on radar. He told me I was still on an IFR flight plan till they acknowledged my cancellation. I am aware of that and thought it had been received when the reply that I could hardly understand was received immediately after I had cancelled. He said they had tried to reach me and other aircraft had tried as well. The only way that would have been possible is if the radios were on the blink when I cancelled. They should have saw a VFR target at 4500 (3500 since it 1000? off sometimes). I told him about my radio issue. He told me he would review the tapes again. However; I can not help what goes wrong enroute. At RSN I made sure the external screws on the wires connected to the voltage regulator were tight. I did let them know I had been having radio problems previously and if I did not talk to them I had lost my radios.

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.