EMER COMMAND AUTH USED BY PIC OF B757 FOR UNAUTH UNCOORD DSCNT PROC AFTER AN INFLT ENCOUNTER WITH SEVERE CLR AIR TURB.

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ENRTE LAX-OGG; XA50Z; WBOUND TRACK D 90E DANKA; FL350; MACH .79. FLT ENCROACHED AREA OF MODERATE CHOP WITH NO SIGNIFICANT RADAR RETURNS. SEAT BELT SIGN ILLUMINATED WITH ANNOUNCEMENT. REQUESTED DSCNT TO FL290. HNL RADIO ADVISED 'STANDBY.' CHOP RAPIDLY INTENSIFIED TO LIGHT TO MODERATE TURB WITH OCCASIONAL SEVERE JOLTS. FLT ATTENDANTS ORDERED TO BE SEATED. MADE SECOND REQUEST FOR IMMEDIATE DSCNT FL280. HNL RADIO ADVISED; 'NO ANSWER FROM ATC; REXMITTING; STANDBY.' FL350 UNINHABITABLE. INITIATED OCEANIC EMER WX DEV PROCS. DISPLACED LATERALLY FROM TRACK; THEN INITIATED DSCNT TOWARDS FL285. XMITTED PAN- PAN-PAN AND INTENTIONS ON HF AND VHF GUARD. TCASII INDICATED NO CONFLICTING TARGETS. RECEIVED ATC CLRNC TO FL290. RECEIVED AMENDED ATC CLRNC TO FL270 DUE OTHER DSNDING TFC. CLRED TO REJOIN TRACK D AT DUFFEE FL270. REQUESTED HNL RADIO RELAY TURB RPT TO DFW DISPATCH. NO PAX OR FLT ATTENDANT INJURIES RPTED FROM CABIN. NO INDICATION OF EQUIP DAMAGE. E6 ENTRY AND MAINT NOTIFIED. FLT CONTINUED AND LANDED OGG WITHOUT FURTHER INCIDENT.