Have you ever been flying over the Atlantic in a two-engine aircraft and wondered what would happen if your plane lost the function of one of its engines? Well, civil aviation authorities have long thought about this as well. That’s why today we have ETOPS rules. Developed as a standard in the 1980s, these specifications have greatly shaped the development of commercial aircraft.
ETOPS is an acronym that stands for “Extended-range Twin-engine Operational Performance Standards”.
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. This means 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.
Shortly after, the ICAO recommended a 90-minute diversion time for all aircraft, which was adopted by many regulatory authorities and airlines outside the US.
Things have come a long way since then in terms of confidence in the reliability of aircraft and their engines. 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.
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.
FlightGlobal reported that a particular Rolls-Royce engine was given this increased rating:
“EASA lists a maximum diversion duration of 420min for the Trent XWB-97, including 405min at maximum continuous thrust plus 15min at hold thrust.”
Shaping aircraft development
“It’ll be a cold day in hell before I let twins fly long-haul over-water routes” – Lynn Helms, former FAA Administrator
For good reason, civil aviation authorities wanted to ensure that aircraft were able to fly far enough to a suitable airport should something happen to an engine. Therefore, as the video below explains, airlines would get around ETOPS restrictions by using quad-jets or tri-jets for their trans-oceanic routes.
In fact, the A340 was developed to get around ETOPS restrictions by having four engines but a smaller capacity than the 747 – perhaps the original attempt to answer the “long and skinny” route requirements.
Increases in ETOPS ratings have more or less meant the end of quad-jet aircraft. There were no longer any regulatory restrictions mandating more than two engines to fly over an ocean. As a result, airlines now opt for two engine aircraft as they are much easier to maintain. As a result, manufacturers have focused on twin-jet aircraft and work hard with engine manufacturers to increase engine reliability.
The bottom line
Higher and higher ETOPS certifications are an indication of increased reliability and safety. As aircraft manufacturers work to increase the range and efficiency of their aircraft, engine manufacturers must keep up with ever-increasing standards for reliability.
Therefore, with longer routes across oceans, the flying public should feel safer knowing that newer jets are achieving these increased ratings.