Narrative:

We were cleared to 'enter and back track runway 9' by george charles tower. The crew was performing taxi checks during the back taxi when tower called to deliver the ATC clearance. After giving the clearance, tower said, 'on the turn, cleared for takeoff,' which the first officer read back. The crew held in position for 2-3 mins while completing departure brief, taxi checks and takeoff checks. The first officer's microphone switch apparently stuck during the 'prepare for takeoff' PA, because the flight attendant informed the crew that the taxi checks had gone out over the PA. The first officer switched his transmit to VHF #1 and unwittingly sent takeoff checks over tower frequency. The tower controller apparently was perturbed by the delay and the over-frequency checklist. He may have also thought that the crew was waiting for takeoff clearance then just went when they got impatient (perhaps reading the checklist over the air to register their frustration?). These are only guesses as to why, but for whatever reason, the tower controller forgot that he had cleared the aircraft for takeoff. As the aircraft passed 500 ft MSL, the tower controller scolded the crew for taking off without a clearance and for reading the checklist over the radio. The captain corrected the controller, reminding him that he had given 'on the turn, cleared for takeoff,' and apologized for the communications problem. In my view, the crew made no error. The tower made an honest mistake and forgot that he had already issued takeoff clearance. Nevertheless, there are 2 safety issues to note: 1) tower might have cleared other aircraft or vehicles onto the runway with an aircraft about to roll. 2) despite his believe that the flight was not cleared, the controller made no effort to either clear or stop the aircraft when he saw it start to roll!

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Original NASA ASRS Text

Title: ATR42 CREW ADVISED BY ATC THAT THEY DEPARTED WITHOUT TKOF CLRNC AT TLPC.

Narrative: WE WERE CLRED TO 'ENTER AND BACK TRACK RWY 9' BY GEORGE CHARLES TWR. THE CREW WAS PERFORMING TAXI CHKS DURING THE BACK TAXI WHEN TWR CALLED TO DELIVER THE ATC CLRNC. AFTER GIVING THE CLRNC, TWR SAID, 'ON THE TURN, CLRED FOR TKOF,' WHICH THE FO READ BACK. THE CREW HELD IN POS FOR 2-3 MINS WHILE COMPLETING DEP BRIEF, TAXI CHKS AND TKOF CHKS. THE FO'S MIKE SWITCH APPARENTLY STUCK DURING THE 'PREPARE FOR TKOF' PA, BECAUSE THE FLT ATTENDANT INFORMED THE CREW THAT THE TAXI CHKS HAD GONE OUT OVER THE PA. THE FO SWITCHED HIS XMIT TO VHF #1 AND UNWITTINGLY SENT TKOF CHKS OVER TWR FREQ. THE TWR CTLR APPARENTLY WAS PERTURBED BY THE DELAY AND THE OVER-FREQ CHKLIST. HE MAY HAVE ALSO THOUGHT THAT THE CREW WAS WAITING FOR TKOF CLRNC THEN JUST WENT WHEN THEY GOT IMPATIENT (PERHAPS READING THE CHKLIST OVER THE AIR TO REGISTER THEIR FRUSTRATION?). THESE ARE ONLY GUESSES AS TO WHY, BUT FOR WHATEVER REASON, THE TWR CTLR FORGOT THAT HE HAD CLRED THE ACFT FOR TKOF. AS THE ACFT PASSED 500 FT MSL, THE TWR CTLR SCOLDED THE CREW FOR TAKING OFF WITHOUT A CLRNC AND FOR READING THE CHKLIST OVER THE RADIO. THE CAPT CORRECTED THE CTLR, REMINDING HIM THAT HE HAD GIVEN 'ON THE TURN, CLRED FOR TKOF,' AND APOLOGIZED FOR THE COMS PROB. IN MY VIEW, THE CREW MADE NO ERROR. THE TWR MADE AN HONEST MISTAKE AND FORGOT THAT HE HAD ALREADY ISSUED TKOF CLRNC. NEVERTHELESS, THERE ARE 2 SAFETY ISSUES TO NOTE: 1) TWR MIGHT HAVE CLRED OTHER ACFT OR VEHICLES ONTO THE RWY WITH AN ACFT ABOUT TO ROLL. 2) DESPITE HIS BELIEVE THAT THE FLT WAS NOT CLRED, THE CTLR MADE NO EFFORT TO EITHER CLR OR STOP THE ACFT WHEN HE SAW IT START TO ROLL!

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.