Narrative:

Arrived gvw using CTAF. WX was VMC and we landed using visibility approach. Refueled aircraft and began taxi with passenger at ox:05. We failed to realize the tower opened at ox:00. To make matters worse, the first officer was inadvertently announcing our intentions on frequency 122.95 (unicom) instead of approximately 124.2 (CTAF). As we were beginning our taxi, a civilian small aircraft had just landed and was taxiing to cargo ramp. We decided to back-taxi on runway 18 for departure to avoid taxi conflict. Before taxiing onto runway we made a thorough visibility check for traffic. Just as we taxied onto runway, tower called on frequency 122.95 and made us aware of incursion. As PF, I should have verified the frequency that PNF was transmitting on. We were aware that tower was part-time operational, but should have been more aware of actual hours of operation then getting passenger in the air. Traffic conflict did not occur at any time; however, some military aircraft that use the airport are difficult to see, even in the best VMC's.

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Original NASA ASRS Text

Title: FLT CREW OF VFR ATX TAXIING TO DEPART PART-TIME TWR ARPT BACK-TAXIED ON RWY NOT REALIZING TWR HAD OPENED FOR OPERATION AND CTL.

Narrative: ARRIVED GVW USING CTAF. WX WAS VMC AND WE LANDED USING VIS APCH. REFUELED ACFT AND BEGAN TAXI WITH PAX AT OX:05. WE FAILED TO REALIZE THE TWR OPENED AT OX:00. TO MAKE MATTERS WORSE, THE F/O WAS INADVERTENTLY ANNOUNCING OUR INTENTIONS ON FREQ 122.95 (UNICOM) INSTEAD OF APPROX 124.2 (CTAF). AS WE WERE BEGINNING OUR TAXI, A CIVILIAN SMA HAD JUST LANDED AND WAS TAXIING TO CARGO RAMP. WE DECIDED TO BACK-TAXI ON RWY 18 FOR DEP TO AVOID TAXI CONFLICT. BEFORE TAXIING ONTO RWY WE MADE A THOROUGH VIS CHK FOR TFC. JUST AS WE TAXIED ONTO RWY, TWR CALLED ON FREQ 122.95 AND MADE US AWARE OF INCURSION. AS PF, I SHOULD HAVE VERIFIED THE FREQ THAT PNF WAS XMITTING ON. WE WERE AWARE THAT TWR WAS PART-TIME OPERATIONAL, BUT SHOULD HAVE BEEN MORE AWARE OF ACTUAL HRS OF OPERATION THEN GETTING PAX IN THE AIR. TFC CONFLICT DID NOT OCCUR AT ANY TIME; HOWEVER, SOME MIL ACFT THAT USE THE ARPT ARE DIFFICULT TO SEE, EVEN IN THE BEST VMC'S.

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.