AN ACR DC10 CREW SOLVED THEIR ACFT EQUIP PROB BLOWN PNEUMATIC DUCT AND ENG FIRE WARNING RATHER THAN RETURN LAND.

Narrative

#3 ENG FIRE WARNING SHORTLY AFTER TKOF. SLATS EXTENDED -- FLAPS RETRACTED. LEVELED ACFT AT 6000 FT MSL AND COPLT (DC10 FLT INSTRUCTOR; GIVING FIRST LEG OF IOE TO MD80 TRANSITION CAPT) AND FE (EXPERIENCED DC10) INITIATED ENG FAIL/FIRE CHKLIST. CAPT FLEW ACFT; HANDLED RADIOS. WHILE RETARDING #3 THROTTLE THROUGH 60-70 PERCENT N1; ENG FIRE LIGHT WENT OUT. ENG FIRE SYS TESTED OK. CONTACTED ATC AND RECEIVED DELAY VECTOR BACK TOWARD IAH. CONTINUED FLT WITH #3 ENG AT 67 PERCENT N1 AS PER CHKLIST. DID NOT DUMP FUEL. CONTACTED MAINT CTL ON VHF WHO CONCURRED THAT IT WAS PNEUMATIC PROB. COPLT AND FE TROUBLESHOT PNEUMATIC SYS #1; #2 AND #3 AND SUSPECTED FAILURE TO BE BLOWN HIGH PRESSURE PNEUMATIC DUCT BTWN #3 ENG AND #3 ENG BLEED VALVE. (5 MIN DELAY FOR TROUBLE SHOOTING). WITH AGREEMENT FROM MAINT CTL; ADDED PWR ON #3 ENG TO MAX CONTINUOUS THRUST FOR 5 MINS WITH NO FIRE WARNING INDICATION. FIRE WARNING SYS TESTED GOOD AND CREW ELECTED TO EVALUATE SYS WHILE CONTINUING ON TO LONDON. UPON ARR LONDON; FOUND #3 ENG 8TH STAGE DUCT BLOWN. FLT WAS NORMAL IN ALL OTHER RESPECTS.