Narrative:

The flight started at the gate with a deferred APU. This is important because I believe this whole event was part of a chain of events starting with the APU being deferred. The ATIS outside air temperature in ZZZ was reported at 37 degrees C (99 degrees F). The cabin temperature (with 50 passenger on board) was 38 degrees C at the gate. Ramp personnel informed us there was no conditioned air for them to hook up. We hooked up the huffer cart (for engine start) and got a small amount of air movement through the packs. On pushback; I decided to start both engines to maximize what little air conditioning we would get. We were given clearance to taxi to runway 19R which was a much longer taxi than runway 19L; but we needed the length for performance with the deferred APU. I briefed the first officer that when we got to the long taxiway parallel to runway 19R we would run the engines up to try to give a little more air to the packs while respecting the brake temperature monitoring system temperatures. They were all indicating 3's at the midpoint of the taxi. As we neared the end of the runway (we'd completed the 'before takeoff' checklist); the right outboard brake temperature monitoring system climbed rapidly (over a period of about 60 seconds) to a brake temperature monitoring system of 13. The 'brakes overheat' aural and message came on and at that time we declared an emergency and evacuate/evacuationed the plane. At my discretion; I omitted the pressing of the emergency depressurization and the engine fire switches since we knew the problem was isolated to the brakes. On a side note; the operations person who helped us out noted an air temperature of 100 degrees F (where the plane was located) and a ground temperature (he had this measuring device in his truck) of 110 degrees F (in the shade). The passenger were evacuate/evacuationed 100 yards from the aircraft and were loaded onto a van back to the gate within 10 mins.

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Original NASA ASRS Text

Title: DISPATCHED WITH THE APU INOP; CARJ FLT CREW UTILIZES HIGHER ENG THRUST IN AN ATTEMPT TO COOL CABIN ON TAXI OUT. COMBINED WITH HIGH AMBIENT TEMPS; A BRAKE OVERHEAT RESULTS AND THE ACFT IS EVACED.

Narrative: THE FLT STARTED AT THE GATE WITH A DEFERRED APU. THIS IS IMPORTANT BECAUSE I BELIEVE THIS WHOLE EVENT WAS PART OF A CHAIN OF EVENTS STARTING WITH THE APU BEING DEFERRED. THE ATIS OUTSIDE AIR TEMP IN ZZZ WAS RPTED AT 37 DEGS C (99 DEGS F). THE CABIN TEMP (WITH 50 PAX ON BOARD) WAS 38 DEGS C AT THE GATE. RAMP PERSONNEL INFORMED US THERE WAS NO CONDITIONED AIR FOR THEM TO HOOK UP. WE HOOKED UP THE HUFFER CART (FOR ENG START) AND GOT A SMALL AMOUNT OF AIR MOVEMENT THROUGH THE PACKS. ON PUSHBACK; I DECIDED TO START BOTH ENGS TO MAXIMIZE WHAT LITTLE AIR CONDITIONING WE WOULD GET. WE WERE GIVEN CLRNC TO TAXI TO RWY 19R WHICH WAS A MUCH LONGER TAXI THAN RWY 19L; BUT WE NEEDED THE LENGTH FOR PERFORMANCE WITH THE DEFERRED APU. I BRIEFED THE FO THAT WHEN WE GOT TO THE LONG TXWY PARALLEL TO RWY 19R WE WOULD RUN THE ENGS UP TO TRY TO GIVE A LITTLE MORE AIR TO THE PACKS WHILE RESPECTING THE BRAKE TEMP MONITORING SYS TEMPS. THEY WERE ALL INDICATING 3'S AT THE MIDPOINT OF THE TAXI. AS WE NEARED THE END OF THE RWY (WE'D COMPLETED THE 'BEFORE TKOF' CHKLIST); THE R OUTBOARD BRAKE TEMP MONITORING SYS CLBED RAPIDLY (OVER A PERIOD OF ABOUT 60 SECONDS) TO A BRAKE TEMP MONITORING SYS OF 13. THE 'BRAKES OVERHEAT' AURAL AND MESSAGE CAME ON AND AT THAT TIME WE DECLARED AN EMER AND EVACED THE PLANE. AT MY DISCRETION; I OMITTED THE PRESSING OF THE EMER DEPRESSURIZATION AND THE ENG FIRE SWITCHES SINCE WE KNEW THE PROB WAS ISOLATED TO THE BRAKES. ON A SIDE NOTE; THE OPS PERSON WHO HELPED US OUT NOTED AN AIR TEMP OF 100 DEGS F (WHERE THE PLANE WAS LOCATED) AND A GND TEMP (HE HAD THIS MEASURING DEVICE IN HIS TRUCK) OF 110 DEGS F (IN THE SHADE). THE PAX WERE EVACED 100 YARDS FROM THE ACFT AND WERE LOADED ONTO A VAN BACK TO THE GATE WITHIN 10 MINS.

Data retrieved from NASA's ASRS site as of January 2009 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.