PLT OF A PA34-200 RPTS THAT ON FINAL APCH TO A HIGH ALT ARPT; 1 ENG QUIT. AFTER LNDG; THE SECOND ENG QUIT.

Narrative

DURING APCH TO LNDG AT 7500 FT MSL (500 FT AGL) WITH MIXTURE FULL RICH AND THROTTLES IDLE; THE R ENG STOPPED WORKING. A SAFE LNDG WAS MADE AND AFTER THE ROLLOUT AND SUBSEQUENT TURNOFF; THE L ENG STOPPED WORKING ON THE TXWY WITH FULL MIXTURE AND IDLE THROTTLE. THE PLANE WAS PARKED OVERNIGHT. AFTER TALKING TO AN A&P MECH OVER THE PHONE; I DECIDED THE PROB WAS TOO RICH A MIXTURE FOR A HIGH ALT LNDG. IN THE MORNING; BOTH ENGS STARTED; WERE LEANED FOR HIGH ALT TKOF; AND VFR FLT WAS CONDUCTED TO HOME BASE. I WROTE BOTH ENGS FOR MAINT TO HAVE THE MIXTURES ADJUSTED; AS I FELT ENGS SHOULD NOT QUIT WITH THROTTLES IDLE AND MIXTURES FULL RICH EVEN AT HIGH ALT. IN RETROSPECT; I SHOULD HAVE DONE 2 THINGS: 1) REALIZED A HIGH ALT LNDG DOES NOT REQUIRE FULL MIXTURES; AND 2) I SHOULD HAVE HAD AN A&P MECH LOOK OVER THE ENGS PRIOR TO CONDUCTING FLT; AS PLTS ARE DEFINITELY NOT SUPPOSED TO DIAGNOSE ENG PROBS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR WAS UNABLE TO RESTART THE ENGS AFTER LNDG AND IT WAS NECESSARY TO TOW THE ACFT TO PARKING. ALTHOUGH ABLE TO START THE ENGS THE FOLLOWING MORNING; DOING SO REQUIRED ABOUT 1/2 HR; WELL BEYOND THE NORM. RPTR ADVISED THAT MAINT WAS UNABLE TO DETERMINE ANY FAULTS AND THE ACFT WAS RETURNED TO SVC. THE CHIEF PLT SUGGESTED AT A COMPANY PLT'S MEETING THAT FLT CREWS SHOULD EXERCISE PRUDENCE IN MIXTURE OPS AT HIGH DENSITY ALT FIELDS. RPTR STATED THERE WAS NO DEFINITION OF WHAT PRUDENT ACTION WOULD ENTAIL AND THAT NO SPECIFIC PROC WAS DEVELOPED OR AUTHORIZED. RPTR REVIEWED THE POH DURING THE CALLBACK AND WAS UNABLE TO FIND ANY REF TO AMENDED OR ABNORMAL LNDG OPS BASED ON ARPT DENSITY ALT.