Flying over the atlantic and suddenly you go, ”What would happen if one of the engines fails?”. Just me?! Perhaps. Maybe not!
Well, the civil aviation authorities have long thought about this too.And that’s exactly why we have the ETOPS rules. Initially developed as a standard in the 1980s, they have come a long way in shaping the commercial aircrafts we see today.
In simple terms, ETOPS is an acronym that stands for “Extended-range Twin-engine Operational Performance Standards”. Basically, ETOPS is a set of rules that enhance safety when flying over areas of the world that have few airports that can be used in an emergency.
- In 1985, special allowance was given to Trans World Airlines to fly their twin-engine 767 transatlantic from Boston to Paris. This was the first ETOPS certification rating given: ETOPS 120 minutes-meaning that twin-engine aircraft were allowed to fly no more than 120 minutes flying time away from the nearest airport suitable for an emergency landing.
Decades prior to this, the FAA had a “60-minute rule” that restricted twin-engine aircraft to a 60-minute diversion area. This number was based on the piston engine reliability of the time but the rule had some flexibility pending special approval.
The 60 minute rule
Airliners with two engines can fly any route that remains within 60 minutes flying time of an airport that is adequate for landing in the event of an emergency. The 60 minute distance is calculated using the aircraft’s speed with one engine inoperative in still air (no wind).
How is ETOPS calculated?
- For instance, a selected one-engine inoperative cruise speed of 400 knots will result in an ETOPS area of applicability of 1200 NM (ie. 400 knots x 3 hours= 1200 NM). Any flight whose route will take the airplane more than 1200 NM from an adequate airport would require the certificate holder to have ETOPS authorization.
Types of ETOPS ratings
Typical two-engine ratings are ETOPS-120 (minutes) and ETOPS-180. The higher the rating, the more difficult and costly it is to receive and maintain approval.
Raising the bar
- According to wikipedia, ETOPS 120 became the standard but this gave way to ETOPS 180. Achieving this increased rating was only possible after a year of trouble-free 120-minute ETOPS experience. Eventually, the FAA was convinced to allow ETOPS 180 on an aircrafts’ entry into service. Things have come a long way since then in terms of confidence in the reliability of aircraft and their engines.
- Now ETOPS certifications go as high as 370 with the Airbus A350. Reports from 2014 indicate that Airbus was seeking ETOPS 420. However, not much reporting exists regarding an aircraft achieving this certification.
- ICAO Annex 6 Part 1 under Amendment 36 introduced the Extended Diversion Time Operations (EDTO) regime in place of ETOPS
- However, the term ‘ETOPS’ has been retained by the FAA and others by redefining it as an abbreviation for ‘Extended Range Operations’ rather than as previously ‘Extended Range Twin Operations’.
- EASA currently continues to use ETOPS as originally defined and the abbreviation ‘LROPS’ (Long Range OPerationS) for extended range operation by three and four-engined aircraft.