Narrative:

On 6/fri/90 at approximately xx:45 pm (prior to 2000) local time, I was inbound from the north to arb at approximately 9 mi north of the field. I tried to contact arb tower on 120.3 with no response. Having detroit metropolitan current ATIS information for wind direction, speed and current altimeter setting, I switched frequency to 123.0 (arb unicom) and announced my intentions of approach and landing at arb. Again, no response. At about 3/4 mi north of the field I announced on 123.0 that I was entering left downwind for runway 06. Again, no response, so I continued on base and then final, maintaining traffic sep landed with no incident. Upon clearing active runway I announced on 123.0 clear of active. All during this time I was monitoring 121.6 (which is arb ground control). After clearing the active I was taxiing to center field tie down area. When ground tried to contact me asking what my intentions were and why I had not contacted tower on my approach, I explained that I had tried to contact them with no response, so I figured the tower was closed and used the frequency. He informed me that I should use my airport directory to find out when the tower was closed, 2000 local. It is my understanding that during the time the tower is in operation, that it monitors the unicom frequency so that if someone is using unicom while tower is in operation, they can inform them of this and provide information for frequency change. I acquired frequency information from 1990 mi chart, which says 'C.T. 120.3*,' asterisk meaning consult NOTAMS for opal hours 0800 to 2000 local and unicom 123.0. I have since contacted arb tower to discuss this and was told that 123.0 was used for ground service frequency and that 120.3 was supposed to be used even after the tower was closed. If this is true there should be no unicom listed on chart!

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Original NASA ASRS Text

Title: UNAUTH LNDG.

Narrative: ON 6/FRI/90 AT APPROX XX:45 PM (PRIOR TO 2000) LCL TIME, I WAS INBND FROM THE N TO ARB AT APPROX 9 MI N OF THE FIELD. I TRIED TO CONTACT ARB TWR ON 120.3 WITH NO RESPONSE. HAVING DETROIT METRO CURRENT ATIS INFO FOR WIND DIRECTION, SPD AND CURRENT ALTIMETER SETTING, I SWITCHED FREQ TO 123.0 (ARB UNICOM) AND ANNOUNCED MY INTENTIONS OF APCH AND LNDG AT ARB. AGAIN, NO RESPONSE. AT ABOUT 3/4 MI N OF THE FIELD I ANNOUNCED ON 123.0 THAT I WAS ENTERING L DOWNWIND FOR RWY 06. AGAIN, NO RESPONSE, SO I CONTINUED ON BASE AND THEN FINAL, MAINTAINING TFC SEP LANDED WITH NO INCIDENT. UPON CLRING ACTIVE RWY I ANNOUNCED ON 123.0 CLR OF ACTIVE. ALL DURING THIS TIME I WAS MONITORING 121.6 (WHICH IS ARB GND CTL). AFTER CLRING THE ACTIVE I WAS TAXIING TO CTR FIELD TIE DOWN AREA. WHEN GND TRIED TO CONTACT ME ASKING WHAT MY INTENTIONS WERE AND WHY I HAD NOT CONTACTED TWR ON MY APCH, I EXPLAINED THAT I HAD TRIED TO CONTACT THEM WITH NO RESPONSE, SO I FIGURED THE TWR WAS CLOSED AND USED THE FREQ. HE INFORMED ME THAT I SHOULD USE MY ARPT DIRECTORY TO FIND OUT WHEN THE TWR WAS CLOSED, 2000 LCL. IT IS MY UNDERSTANDING THAT DURING THE TIME THE TWR IS IN OP, THAT IT MONITORS THE UNICOM FREQ SO THAT IF SOMEONE IS USING UNICOM WHILE TWR IS IN OP, THEY CAN INFORM THEM OF THIS AND PROVIDE INFO FOR FREQ CHANGE. I ACQUIRED FREQ INFO FROM 1990 MI CHART, WHICH SAYS 'C.T. 120.3*,' ASTERISK MEANING CONSULT NOTAMS FOR OPAL HOURS 0800 TO 2000 LCL AND UNICOM 123.0. I HAVE SINCE CONTACTED ARB TWR TO DISCUSS THIS AND WAS TOLD THAT 123.0 WAS USED FOR GND SVC FREQ AND THAT 120.3 WAS SUPPOSED TO BE USED EVEN AFTER THE TWR WAS CLOSED. IF THIS IS TRUE THERE SHOULD BE NO UNICOM LISTED ON CHART!

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.