Narrative:

Upon contacting ground, I was cleared to taxi to the active runway. After completing a runup inspection, I taxied to the hold lines and attempted to contact the tower, which prompted no response. I also listened for any ATC response to the 2 other aircraft on the south feeder, but no response was given. I attempted to contact the tower 3 additional times with no ATC transmission. During this time, I could hear the other 2 aircraft's xmissions, which sounded similar to CTAF xmissions. In no instance did I hear the words 'clear' or 'cleared,' nor any other indication of tower communication. After the last aircraft departed, I announced that I would be departing runway 33. Proceeding cautiously, I checked for traffic and kept the departing aircraft in sight. On takeoff (about 30' AGL) the tower contacted my aircraft and stated that I was not cleared for takeoff. Upon return to the area, a preliminary inspection indicated a radio failure had occurred. My decision was to divert to an uncontrolled airport outside the arsa. In conclusion: the exchange with ground controller, as well as other aircraft xmissions, led me to believe that the radios were operational. Upon departure, the tower contacted as well as received transmission from my aircraft. My decision to treat addison as uncontrolled was poor, but the perception of the events led to the confused judgement. The post-flight conversation with the controller on duty informed me that the FBO knew but did not inform me about the sporadic radio xmissions the day before. I was also advised that the facility is open from 0600 to 2200, and should never be considered uncontrolled during those hours. My action could have caused conflict, fortunately it did not--and I will be aware for the signs in this type of event in the future.

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Original NASA ASRS Text

Title: GA SMA UNAUTH TKOF.

Narrative: UPON CONTACTING GND, I WAS CLRED TO TAXI TO THE ACTIVE RWY. AFTER COMPLETING A RUNUP INSPECTION, I TAXIED TO THE HOLD LINES AND ATTEMPTED TO CONTACT THE TWR, WHICH PROMPTED NO RESPONSE. I ALSO LISTENED FOR ANY ATC RESPONSE TO THE 2 OTHER ACFT ON THE S FEEDER, BUT NO RESPONSE WAS GIVEN. I ATTEMPTED TO CONTACT THE TWR 3 ADDITIONAL TIMES WITH NO ATC XMISSION. DURING THIS TIME, I COULD HEAR THE OTHER 2 ACFT'S XMISSIONS, WHICH SOUNDED SIMILAR TO CTAF XMISSIONS. IN NO INSTANCE DID I HEAR THE WORDS 'CLR' OR 'CLRED,' NOR ANY OTHER INDICATION OF TWR COM. AFTER THE LAST ACFT DEPARTED, I ANNOUNCED THAT I WOULD BE DEPARTING RWY 33. PROCEEDING CAUTIOUSLY, I CHKED FOR TFC AND KEPT THE DEPARTING ACFT IN SIGHT. ON TKOF (ABOUT 30' AGL) THE TWR CONTACTED MY ACFT AND STATED THAT I WAS NOT CLRED FOR TKOF. UPON RETURN TO THE AREA, A PRELIMINARY INSPECTION INDICATED A RADIO FAILURE HAD OCCURRED. MY DECISION WAS TO DIVERT TO AN UNCONTROLLED ARPT OUTSIDE THE ARSA. IN CONCLUSION: THE EXCHANGE WITH GND CTLR, AS WELL AS OTHER ACFT XMISSIONS, LED ME TO BELIEVE THAT THE RADIOS WERE OPERATIONAL. UPON DEP, THE TWR CONTACTED AS WELL AS RECEIVED XMISSION FROM MY ACFT. MY DECISION TO TREAT ADDISON AS UNCONTROLLED WAS POOR, BUT THE PERCEPTION OF THE EVENTS LED TO THE CONFUSED JUDGEMENT. THE POST-FLT CONVERSATION WITH THE CTLR ON DUTY INFORMED ME THAT THE FBO KNEW BUT DID NOT INFORM ME ABOUT THE SPORADIC RADIO XMISSIONS THE DAY BEFORE. I WAS ALSO ADVISED THAT THE FAC IS OPEN FROM 0600 TO 2200, AND SHOULD NEVER BE CONSIDERED UNCONTROLLED DURING THOSE HRS. MY ACTION COULD HAVE CAUSED CONFLICT, FORTUNATELY IT DID NOT--AND I WILL BE AWARE FOR THE SIGNS IN THIS TYPE OF EVENT IN THE FUTURE.

Data retrieved from NASA's ASRS site as of July 2007 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.