Narrative:

Approaching spaceport executive airport from the south made 3 attempts to contact tower with no response. Checking the airport facilities directory while we circled I thought the tower was still open and tried the tower once more with negative results. I then switched to the listed unicom frequency and heard an aircraft reporting final for runway 36. I visually sighted a cessna on final for runway 36 and assumed tower was closed. I proceeded making all of my traffic calls on the unicom frequency. After a touch and go I was contacted by another aircraft and told to call the tower. The tower said they heard me and had responded. They also told me never to use the unicom frequency, that it is for FBO's. Traffic separation was never a problem in this situation. I believe that only frequencys to be used to support flight operations should be listed on the sectional charts. Administrative frequencys should be (and are) listed in airport guides and the AFD. After this event took place, I discussed it with 3 other CFI's. One CFI was under the belief, as was I, that when the tower is closed, use the listed unicom frequency.

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Original NASA ASRS Text

Title: UNAUTH PENETRATION OF CLASS D AIRSPACE BY INSTRUCTOR PLT AND STUDENT. UNAUTH LNDG TKOF, TOUCH AND GO, PERFORMED.

Narrative: APCHING SPACEPORT EXECUTIVE ARPT FROM THE S MADE 3 ATTEMPTS TO CONTACT TWR WITH NO RESPONSE. CHKING THE ARPT FACILITIES DIRECTORY WHILE WE CIRCLED I THOUGHT THE TWR WAS STILL OPEN AND TRIED THE TWR ONCE MORE WITH NEGATIVE RESULTS. I THEN SWITCHED TO THE LISTED UNICOM FREQ AND HEARD AN ACFT RPTING FINAL FOR RWY 36. I VISUALLY SIGHTED A CESSNA ON FINAL FOR RWY 36 AND ASSUMED TWR WAS CLOSED. I PROCEEDED MAKING ALL OF MY TFC CALLS ON THE UNICOM FREQ. AFTER A TOUCH AND GO I WAS CONTACTED BY ANOTHER ACFT AND TOLD TO CALL THE TWR. THE TWR SAID THEY HEARD ME AND HAD RESPONDED. THEY ALSO TOLD ME NEVER TO USE THE UNICOM FREQ, THAT IT IS FOR FBO'S. TFC SEPARATION WAS NEVER A PROB IN THIS SIT. I BELIEVE THAT ONLY FREQS TO BE USED TO SUPPORT FLT OPS SHOULD BE LISTED ON THE SECTIONAL CHARTS. ADMINISTRATIVE FREQS SHOULD BE (AND ARE) LISTED IN ARPT GUIDES AND THE AFD. AFTER THIS EVENT TOOK PLACE, I DISCUSSED IT WITH 3 OTHER CFI'S. ONE CFI WAS UNDER THE BELIEF, AS WAS I, THAT WHEN THE TWR IS CLOSED, USE THE LISTED UNICOM FREQ.

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.