AN FO DEPLORES HIS CREW'S ATTITUDE TOWARDS A TAIL OVERHEAT WARNING AND TSTM AVOIDANCE.

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WE DEPARTED PHX WITH A CHK AIRMAN IN THE COCKPIT JUMPSEAT; NOT ON OFFICIAL BUSINESS; HE WAS RETURNING FROM A PERSONAL TRAVEL TRIP. THE RPTED AMBIENT TEMP ON THE PHX ATIS WAS 105 DEGS F AND THE CAPT ELECTED TO LEAVE THE APU RUNNING FOR TKOF TO PROVIDE FOR INCREASED COOLING OF THE AFT TAIL COMPARTMENT AREA AS PROVIDED FOR IN THE FLT HANDBOOK PROCS SECTION. IT IS COMMON KNOWLEDGE THAT; DURING HIGH AMBIENT TEMP DAYS; TAIL COMPARTMENT TEMP HI ANNUNCIATOR MAY ILLUMINATE. OUR COMPANY PROC IS TO LEAVE THE APU RUNNING TO PROVIDE FOR INCREASED AIR FLOW IN THE TAIL COMPARTMENT AREA TO HELP PREVENT 'NUISANCE' WARNINGS. UNFORTUNATELY; EVEN THOUGH WE FOLLOWED THE RECOMMENDED PROC; THE TAIL COMPARTMENT TEMP HI ANNUNCIATOR DID IN FACT ILLUMINATE. I WAS THE FIRST PERSON TO VERBALIZE THAT THE TAIL COMPARTMENT TEMP HI ANNUNCIATOR WAS ILLUMINATED. THE CAPT ACKNOWLEDGED THAT HE WAS AWARE OF THE SIT AND VIA THE QRH CHKLIST; ACCOMPLISHED THE TAIL COMPARTMENT TEMP HIGH PROC. BEFORE THE ENTIRE CHKLIST WAS COMPLETED;THE ANNUNCIATOR LIGHT WENT OUT ON ITS OWN. THE ENTIRE CHKLIST WAS COMPLETED AND WE (THE CAPT; CHK AIRMAN; AND MYSELF) HAD A BRIEF DISCUSSION ABOUT HOW COMMON THIS NUISANCE WARNING OCCURS IN HIGH AMBIENT TEMPS AND HOW; WHEN IT OCCURS DURING THESE CONDITIONS; IT OFTEN TENDS TO BE DISCOUNTED BY THE FLC AS AN ERRONEOUS WARNING. LATER; IT BECAME NECESSARY TO DIVERT AROUND SOME TSTM BUILD-UPS. IN THE DISTANCE WE WOULD SEE 2 BUILD-UPS AHEAD AND THESE SAME BUILD-UPS WERE PAINTING ON THE WX RADAR. I STATED TO THE CAPT; 'WHICH WAY DO YOU WANT TO TURN; L OR R?' HE RESPONDED; 'I THINK THAT WE CAN TOP THEM AND WON'T NEED TO DIVERT AROUND THEM.' AT THAT TIME; WE WERE STILL IN THE CLB AND WERE STILL 40 PLUS MI FROM THE BUILD-UPS AND THERE WAS NO FURTHER DISCUSSION ABOUT THIS MATTER. SHORTLY AFTER THIS DISCUSSION; THE CHK AIRMAN EXCUSED HIMSELF FROM THE COCKPIT AND WE DID TOP THE BUILD-UPS AND PASS BTWN THEM AS THEY WERE SPACED SLIGHTLY L AND SLIGHTLY R OF OUR FLT PATH. AS WE TRANSITIONED THE AREA WE DID; HOWEVER; ENCOUNTER SOME LIGHT TO MODERATE TURB. AFTER THE RIDE SMOOTHED BACK OUT; I GOT UP AND WENT BACK TO THE LAVATORY AT WHICH TIME THE CHK AIRMAN REMARKED; 'WHAT DID YOU GUYS DECIDE...TO FLY THROUGH THOSE BUILD-UPS?' I ASSURED HIM THAT WE DID AVOID THE BUILD-UPS; ALTHOUGH THE RIDE MAY NOT HAVE BEEN INDICATIVE OF THAT. IT IS BEST NOT TO ASSUME; OR EVEN INFER; THAT; ALTHOUGH THE AMBIENT TEMP IS HIGH; AN ABNORMAL INDICATION SHOULD BE TAKEN ANY LESS SERIOUSLY. ANY IMMEDIATE ACTION ITEMS SHOULD BE ACCOMPLISHED IN A TIMELY FASHION AND THEN FOLLOWED BY THE USE OF THE QRH PROC. FOR IMPROVED PAX COMFORT; DEV AROUND TSTM BUILD-UPS AS DESCRIBED IN OUR FLT HANDBOOK RECOMMENDS AVOIDING ALL ECHOES BY 20 NM ABOVE FL230 AND TOPPING ALL ECHOES BY 5000 FT. THIS GUIDANCE WOULD CERTAINLY PROVIDE FOR A MUCH MORE COMFORTABLE FLT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR FLIES THE MD-80 FOR A SECOND LEVEL UNITED STATES ACR. THIS OVERHEAT SIT HAPPENS SO FREQUENTLY THAT 'IT IS EASY TO BECOME COMPLACENT ABOUT IT.' THE RPTR HAS HEARD THAT THE UNITED STATES NAVY BURNED UP AN ACFT WITH THE SAME PROB. THE MD-80 IS WELL KNOWN FOR AIR CONDITIONING DUCT LEAKS; SO IT IS NOT WISE TO IGNORE THIS WARNING. THE RPTR KNOWS OF NO FIX IN THE WORKS FOR THIS PROB.