Narrative:

In process of departing mgm for bna. As aircraft was close to gross weight, and because of high ambient temperatures, automatic power reserve was required for takeoff. Automatic power reserve use involves a test of that system plus the torque/temperature limiter computer prior to flight. These tests are normally done on the runway just before commencing the takeoff roll. Tower was advised that we needed a short period prior to takeoff. Flight was cleared 'in position and hold, advise when ready.' we taxied into position and did the tests. When the checks were done the power was at 65 percent. At that point the first officer announced 'before takeoff check complete.' without a thought to our clearance I advanced the power to takeoff setting and commenced the roll. Well into the roll the tower said 'cleared for takeoff.' at that point we realized we had rolled without a clearance. Cause of incident: inattn. 2 factors contributed: 1) habit pattern broken. I do not normally advise the tower of a need to delay in position as the automatic power reserve and ttl checks take no more than 30-40 seconds to complete. Once takeoff clearance is received, I run the checks and go. 2) fatigue. Both crew members were tired and had commented earlier on how tiring the day had been. I had been awakened at approximately 13 hours prior and informed of the assignment. My day involved a deadhead from rdu to bna then 3 legs, bna-owb-bna-mgm. Throughout the period aircraft cabin had been in high 80's to low 90's degrees F. Cockpit is usually warmer but there is no gauge to tell what temperature is there. Flight conditions were not a factor but long exposure to heat was. In this regard, the company does not have sufficient cooling equipment. Saab's and F17R's have priority. As a result, jetstreams often are dispatched with cockpits/cabins above 85 degrees F. In our case, left bleed air system was out of commission. This contributed to lower than normal cooling once engines were started. On board freon unit is in rear of aircraft and does little to cool cockpit. Prolonged exposure to high temperatures takes its toll on crew alertness. It is also worth noting that when you are uncomfortable -- and we were -- that one's mind tends to focus on relieving the discomfort. In this case, getting airborne as soon as possible to let the bleed air system work better.

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Original NASA ASRS Text

Title: FLC OF LTT STARTED TKOF PRIOR TO RECEIVING TKOF CLRNC.

Narrative: IN PROCESS OF DEPARTING MGM FOR BNA. AS ACFT WAS CLOSE TO GROSS WT, AND BECAUSE OF HIGH AMBIENT TEMPS, AUTOMATIC PWR RESERVE WAS REQUIRED FOR TKOF. AUTOMATIC PWR RESERVE USE INVOLVES A TEST OF THAT SYS PLUS THE TORQUE/TEMP LIMITER COMPUTER PRIOR TO FLT. THESE TESTS ARE NORMALLY DONE ON THE RWY JUST BEFORE COMMENCING THE TKOF ROLL. TWR WAS ADVISED THAT WE NEEDED A SHORT PERIOD PRIOR TO TKOF. FLT WAS CLRED 'IN POS AND HOLD, ADVISE WHEN READY.' WE TAXIED INTO POS AND DID THE TESTS. WHEN THE CHKS WERE DONE THE PWR WAS AT 65 PERCENT. AT THAT POINT THE FO ANNOUNCED 'BEFORE TKOF CHK COMPLETE.' WITHOUT A THOUGHT TO OUR CLRNC I ADVANCED THE PWR TO TKOF SETTING AND COMMENCED THE ROLL. WELL INTO THE ROLL THE TWR SAID 'CLRED FOR TKOF.' AT THAT POINT WE REALIZED WE HAD ROLLED WITHOUT A CLRNC. CAUSE OF INCIDENT: INATTN. 2 FACTORS CONTRIBUTED: 1) HABIT PATTERN BROKEN. I DO NOT NORMALLY ADVISE THE TWR OF A NEED TO DELAY IN POS AS THE AUTOMATIC PWR RESERVE AND TTL CHKS TAKE NO MORE THAN 30-40 SECONDS TO COMPLETE. ONCE TKOF CLRNC IS RECEIVED, I RUN THE CHKS AND GO. 2) FATIGUE. BOTH CREW MEMBERS WERE TIRED AND HAD COMMENTED EARLIER ON HOW TIRING THE DAY HAD BEEN. I HAD BEEN AWAKENED AT APPROX 13 HRS PRIOR AND INFORMED OF THE ASSIGNMENT. MY DAY INVOLVED A DEADHEAD FROM RDU TO BNA THEN 3 LEGS, BNA-OWB-BNA-MGM. THROUGHOUT THE PERIOD ACFT CABIN HAD BEEN IN HIGH 80'S TO LOW 90'S DEGS F. COCKPIT IS USUALLY WARMER BUT THERE IS NO GAUGE TO TELL WHAT TEMP IS THERE. FLT CONDITIONS WERE NOT A FACTOR BUT LONG EXPOSURE TO HEAT WAS. IN THIS REGARD, THE COMPANY DOES NOT HAVE SUFFICIENT COOLING EQUIP. SAAB'S AND F17R'S HAVE PRIORITY. AS A RESULT, JETSTREAMS OFTEN ARE DISPATCHED WITH COCKPITS/CABINS ABOVE 85 DEGS F. IN OUR CASE, L BLEED AIR SYS WAS OUT OF COMMISSION. THIS CONTRIBUTED TO LOWER THAN NORMAL COOLING ONCE ENGS WERE STARTED. ON BOARD FREON UNIT IS IN REAR OF ACFT AND DOES LITTLE TO COOL COCKPIT. PROLONGED EXPOSURE TO HIGH TEMPS TAKES ITS TOLL ON CREW ALERTNESS. IT IS ALSO WORTH NOTING THAT WHEN YOU ARE UNCOMFORTABLE -- AND WE WERE -- THAT ONE'S MIND TENDS TO FOCUS ON RELIEVING THE DISCOMFORT. IN THIS CASE, GETTING AIRBORNE ASAP TO LET THE BLEED AIR SYS WORK BETTER.

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.