AN S80 CAPT USES EXCESSIVE BRAKING AND INCURS A 50 MIN DELAY FOR BRAKE COOLING PURPOSES. THE APU AIR USED FOR AIR CONDITIONING PURPOSES WAS TOO LOW. SINCE THE CABIN WAS VERY HOT; HE HAD TO USE EXCESSIVE ENG PWR TO KEEP THE PAX COOL.

Narrative

DURING BOARDING; THE CABIN TEMP WAS UNCOMFORTABLY HIGH AND LITTLE OR NO COOLING AIR WAS BEING PROVIDED BY THE APU. FLOW INDICATIONS ON BOTH SIDES WERE NORMAL. WHEN BOTH AIR CONDITIONING SUPPLY SWITCHES WERE TURNED OFF FOR ENG START; THE PNEUMATIC PRESSURE WAS INSUFFICIENT FOR A SAFE START SO A START-CART WAS USED. AFTER PWR BACK; I FOUND THAT 1.06 EPR PER ENG WAS THE MINIMUM PWR REQUIRED TO PRODUCE ANY COOLING AIRFLOW FROM THE PACKS. I TAXIED FROM GATE TO RWY 18L AT THIS PWR TO GET THE CABIN TEMP UNDER CTL. THIS PROC REQUIRED THAT THE BRAKES BE USED ALMOST CONTINUOUSLY DURING TAXI. THE BRAKE TEMPS WERE MONITORED CONSTANTLY DURING THE ENTIRE PROCESS; AND REMAINED AROUND 125-150 THE ENTIRE TIME. AFTER WE HAD REACHED THE RWY HOLD LINE AND WERE STOPPED; THE BRAKE TEMPS ON THE L MAIN WHEELS BEGAN TO CLB AND REACHED 330 DEGS ON THE OUTBOARD WHEEL. A DELAY OF 40 MINS WAS INCURRED WHILE THE BRAKES WERE ALLOWED TO COOL WITH CFR STANDING BY AND WERE INSPECTED BY COMPANY MAINT. THIS ACFT HAD 5 E6 WRITE-UPS OVER THE PREVIOUS 7 DAYS FOR THE APU PRODUCING INSUFFICIENT OR NO AIR AND ALL WERE SIGNED OFF AS OPS CHKED NORMAL. I DON'T KNOW HOW ELSE I COULD HAVE HANDLED THIS SIT OTHER THAN TO REFUSE TO TAKE THE ACFT BASED ON THE PREVIOUS E6 ENTRIES AND THE CURRENT CABIN TEMP BUT THIS WAS NOT PERCEIVED AS A SAFETY ISSUE ALTHOUGH IT LATER BECAME ONE BECAUSE OF THE BRAKES. WHEN WE ARRIVED AT LGA; MAINT SAID THEY WERE GOING TO REPLACE THE APU THAT NIGHT.