The origins of ETOPS (Extended Twin Operations) / EDTO (Extended Diversion Time Operations) and the requirement for awareness stem from the mid 1950’s the ICAO (International Civil Aviation Organisation) standing committee for aircraft performance reviewed engine reliability data of the era and discovered that the 60-minute rule was still of good standing.Read more: ETOPS (Extended Twin Operations) / EDTO (Extended Diversion Time Operations) Awareness.
With the introduction of some large new twin jets like the Airbus A300 (1974) and the Boeing 767 (1982) it was becoming obvious that the airframe and avionics systems also needed reviewing and the ruling was changed several times with the increase in aircraft reliability.
Many of the North Atlantic diversion airports, especially those in Iceland & Greenland are subject to adverse weather conditions making them unavailable for use and so the 180-minute rule became the upper limit, EASA gave a 15% extension to the 120-minute rule to deal with such contingencies.
This limit of 180 minute was then increased and the Airbus A330 was granted ETOPS 240; the Boeing 777 & 787 was granted ETOPS 330 and the Airbus A350 was granted ETOPS 370.
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