Aircraft originally designed to carry passengers short-to-medium distances have stretched their wings over the past decade to embark on transoceanic travel. These include aircraft like the Airbus A321LR and Boeing 737 MAX, developed from versions first introduced in the 1990s. The forthcoming Airbus A321XLR will have a range up to 4,500 nautical miles. Engine and airframe improvements account for the increased range of the aircraft, but without a regulatory framework to support long flights by twin engine aircraft over water, these aircraft wouldn’t exist. Enter ETOPS.
What is ETOPS?
ETOPS, originally short for Extended-Range Twin Operations Performance Standards, or more recently just plain Extended operations, is the rating that allows twin-engined aircraft to fly long distances; particularly over large bodies of water like oceans. This is why it has often been dubbed as standing for “Engines Turn or Passengers Swim.” An ETOPS rating essentially gives the distance away from the nearest diversion airport an aircraft can fly and is based on how many minutes an aircraft can fly on one engine before it needs to land. For instance, an Airbus A330neo with an ETOPS 285 rating can fly anywhere as long as it can make it to an airport available for landing within 285 minutes. ETOPS governs which routes planes fly, and can also have effects on how areas with lower demand receive air traffic. This is because airlines don’t want to fly four-engined aircraft to smaller destinations, as this would be inefficient and costly, meaning that these areas just don’t receive long-haul flights.
Before ETOPS
Prior to the development of ETOPS, twin-engined aircraft were only allowed to fly a distance of 60 minutes away from diversion airports. This was because, before the jet age, all twin-engine aircraft were piston-engined, which were extremely unreliable, and used to fail much more frequently. Federal Aviation Administration (FAA) studies have shown that for every 1 jet-engine failure, there are 117 piston-engine failures. However, in the 1970s when twin jet engines were gaining a foothold in the industry their use was still restricted longer distances over water. This meant that to fly transatlantic to areas which had less demand, airlines would either have to fly an extremely fuel-inefficient route or operate larger aircraft. Therefore, a flight from Philadelphia to Madrid wouldn’t be flying that often, as the only aircraft which could cater to the demand would be smaller, twin-engined aircraft which weren’t allowed economically operate on the route. It also meant that small island nations in oceans like the Pacific wouldn’t receive much air traffic, halting their development, as the routes to reach them were out of the 60-minute boundary.
With the 60 minute limitations in place for twin engined aircraft, trijets gained momentum. Smaller than the 747 and more economical than the DC-8, the DC-10 is a prime example of an aircraft catering to long-haul, lower-demand routes.
And then, revolutionarily, the first ETOPS rating of 120 minutes was given to a Trans World Airlines Boeing 767 in 1985. This meant the airline could now take its 767 across the Atlantic, saving fuel (and money) and spawning new routes and new destinations for travelers across the world.
To receive the appropriate ETOPS ratings, the manufacturer has to prove that flying a set distance with one engine doesn’t damage the airframe and can be managed by the crew. In addition, an airline must prove that once reaching a diversion airport, its crew can manage passengers whilst waiting for rescue authorities to arrive. An example of this is that many diversion airports are in areas where the populations are smaller than the number of passengers, and therefore the airline and crew must be able to provide for landing there with limited emergency resources.
ETOPS’ effects on modern aircraft
ETOPS ratings have brought an entirely new market to the aviation scene, long-haul flights to smaller destinations. Without ETOPS ratings, the Boeing 757 would never have flown on transatlantic routes between cities such as Edinburgh and New York, a route that would have been too inefficient for a much larger four-engine aircraft like the 747. However, every rose has a thorn, and ETOPS ratings have caused the downfall of trijets and quadjets, with very few, aside from the A380 and 747, remaining in regular active service. These aircraft just weren’t as efficient as twin-engined aircraft. But the good far outweighs the bad. ETOPS rules and the quest for ever more efficient aircraft have driven jet engine and airliner development far beyond the original ETOPS 120, with the Airbus A350 now boasting an ETOPS rating of 370 minutes. With such a rating, only intercontinental flight paths over the interior of Antarctica are out of reach.
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