B-767 DEPARTED ON OVERWATER OP WITHOUT BOTH IGNITORS IN OP ON #1 ENG.

Narrative

ON START UP L HAND ENG FAILED TO START ON IGNITOR #1. TRIED IGNITOR #2 AND ENG STARTED NORMALLY. ENRTE TO ORD DISCOVERED THAT MEL STATED THAT BOTH IGNITORS WERE REQUIRED FOR EROPS OPS. CONTINUED TO ORD. SUPPLEMENTAL INFO FROM ACN 273419: SINCE WE HAD COMPLETED ALL PROCS IN THE OPERATING MANUAL; WE CONSIDERED EVERYTHING OK AND DEPARTED. AS I/O; I TOOK FIRST BREAK ABOUT 45 MINS INTO FLT AND RETURNED TO THE COCKPIT 2 HRS AND 50 MINS LATER; WHEN WE WERE WELL INTO THE TRANS-ATLANTIC XING. CA INFORMED ME THEN THAT HE HAD CHKED THE MEL AND DISCOVERED THAT ALL IGNITORS ARE REQUIRED FOR EROPS. MY SUGGESTION IS THAT OPS MANUAL INCLUDE A REMINDER 'CHK MEL' AT THE END OF ANY PROC IN WHICH MEL RESTRS MIGHT APPLY. SUPPLEMENTAL INFO FROM ACN 273414: WE UNDERSTOOD FROM OUR PREVIOUS READING OF THE MEL THAT FLT WAS PERMITTED WITH 1 IGNITOR INOP. ENRTE TO ORD WE DISCUSSED THE PROB FURTHER AND CONSULTED THE MEL WHICH STATES: ALL 4 IGNITORS SHALL BE OPERATIVE FOR ALL INTL FLTS. WHY WE FAILED TO CHK THE MEL ON THE GND I WILL NEVER UNDERSTAND; BUT IT IS SOMETHING I WILL ALWAYS DO IN THE FUTURE.