Narrative:

When we called for power-back at chs, the copilot and I both thought we received clearance to taxi to runway 21. During a slow taxi to runway 21 we had to cross runway 15/33, which was active. We cleared visually and crossed. The first officer then changed to tower frequency. The tower told us ground control had been trying to call us on the frequency we had been monitoring because he had told us to 'expect' runway 21, not cleared to taxi. We were monitoring ground, but never heard a call after the initial call at power-back. We were both aware and alert to the danger, but believed we were cleared and never heard a call to the contrary. My personal solution will be to reconfirm clearance to cross any time more than a few seconds lapses since last cleared. I am aware that lighting systems are being studied and believe they would be a great aid.

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Original NASA ASRS Text

Title: ACR TAXIS WITHOUT CLRNC, CROSSES ACTIVE RWY.

Narrative: WHEN WE CALLED FOR PWR-BACK AT CHS, THE COPLT AND I BOTH THOUGHT WE RECEIVED CLRNC TO TAXI TO RWY 21. DURING A SLOW TAXI TO RWY 21 WE HAD TO CROSS RWY 15/33, WHICH WAS ACTIVE. WE CLRED VISUALLY AND CROSSED. THE F/O THEN CHANGED TO TWR FREQ. THE TWR TOLD US GND CTL HAD BEEN TRYING TO CALL US ON THE FREQ WE HAD BEEN MONITORING BECAUSE HE HAD TOLD US TO 'EXPECT' RWY 21, NOT CLRED TO TAXI. WE WERE MONITORING GND, BUT NEVER HEARD A CALL AFTER THE INITIAL CALL AT PWR-BACK. WE WERE BOTH AWARE AND ALERT TO THE DANGER, BUT BELIEVED WE WERE CLRED AND NEVER HEARD A CALL TO THE CONTRARY. MY PERSONAL SOLUTION WILL BE TO RECONFIRM CLRNC TO CROSS ANY TIME MORE THAN A FEW SECS LAPSES SINCE LAST CLRED. I AM AWARE THAT LIGHTING SYSTEMS ARE BEING STUDIED AND BELIEVE THEY WOULD BE A GREAT AID.

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.