DRG AN EMERG MED SVC (EMS)/MED EVAC FLT, AN UNCONTAINED PWR TURBINE BURST OF THE #1 ENG OCCURRED. DEBRIS FM THE #1 ENG DISABLED THE #2 ENG & SEVERED THE TAIL ROTOR DRIVE SHAFT. THE #2 ENG FIRE LGT ILLUMINATED & THE PLT DISCHARGED THE #2 ENG FIRE EXTINGUISHER. DRG AN AUTOROTATIVE LNDG, THE PLT INCREASED COLLECTIVE TO CLR TREES, AND THE HELICOPTER ROLLED ON ITS SIDE AT TOUCHDOWN. THE PLT, 1 NURSE & THE PATIENT WERE UNHARMED, BUT 2 NURSES RCVD MINOR INJURIES. AN EXAM SHOWEDTHE #2 & #3 BRGS IN THE #1 ENG HAD OVERHEATED & FAILED DUE TO LACK OF LUBRICATION. OIL PASSAGES & JETS TO THE BRGS WERE FND CLOGGED WITH HVY CARBON DEPOSITS. THE ENG COMBUSTOR HOUSING WAS CHNGD APRX 13 FLT HRS BFR THE ACDNT DUE TO A CLOGGEDVENT STRUT; AFTER DRAINING OIL, THE OIL SYS WASN'T FLUSHED, BUT FLUSHING WASN'T REQD. EVIDENCE SHOWED LYC LTS 101-750C-1ENGS WERE SUSCEPTIBLE TO CARBON CLOGGING; THAT THE #2 SEALS TENDED TO ERODE & ALLOW EXCESSIVE HOT GASES INTO THE #2 & #3BRGS. AFTER THE ACDNT, THE FAA ISSUED AD 86-22-05, REQUIRING INCREASED INSPN & MAINT PROCEDURES TO PREVENT RECURRENCE.