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2 Early turbine engine experience 3 Early twin-engine high-bypass turbofan airliners 4 Early ETOPS experience 5 Early ETOPS 6 ETOPS exclusions |
The first transatlantic crossing were done by RAF pilots Alcock and Brown using a twin engined Vickers Vimy in 1919 after a 16 hour flight. However, due to the unreliability of piston engines (see internal combustion engine) then, long distance flight using twin engines are very risky at best. A flagship of the piston era, the 4 engined Lockheed Constellation airliner, whose engines are so unreliable that it was dubbed as 'the most reliable 3 engined airplane flying'!!!
The FAA having recognised the piston engine limitations, in 1953, introduced the '60-minute rules' for 2 and 3 engine airplanes. This implies that the flight path of these airplanes shall not be any further than the distance of 60 minutes flying time from any airports. This forced such airplanes, on certain routes, to fly a dogleg path in order to stay within regulations and are totally excluded from certain other routes due to lack of such en-route airports. The 60-minute period is also called 60-minute diversion period. The totally excluded area is call 'Excluson Zone'.
Turbine engines (see Jet engine) such as Pratt and Whitney JT8D series in the 1950s and 1960s demonstrated that they have much higher thrust and reliability than any then currently available piston engines. It was then powering the 2-engined Boeing 737 series and 3-engined Boeing 727. Because of its excellent record, the '60-minute rules' was waived for 3-engined Boeing 727 allowing it to fly transatlantic. This opened up the way for the development of widebody intercontinental trijets such as Lockheed L-1011 Tristar and McDonnell Douglas DC-10. By then only 2-engined jets were restricted by the '60-minute rules'.History
Early turbine engine experience
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Airbus A300 , the precursor for ETOPS. |
Outside the USA, other countries follow ICAO regulations , which allowed for a 90 minutes diversion time. This was exploited by Airbus by lauching the world's first twin-engined high-bypass turbofan widebody airliner, the Airbus A300 in 1974. It was about three quarter the size DC10s and Tristars and for an equivalent loads for the same distance, is cheaper to operate. The A300 was eagerly snapped up by the airlines the world over. The failure rates of these early high-bypass turbofan engines were almost as good as the JT8D and were nearly 20 times better than piston engines. This fact is not lost to Boeing and the Boeing 757 and the Boeing 767 was the response.
Early ETOPS experience
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Boeing 767-200ER , the ETOPS pioneer |
All the developments in aircraft technologies has led the FAA and the ICAO the realisations that it is possible and perfectly safe for a properly designed twin-engined airliners to conduct intercontinental transoceanic flights. The guidelines issued thereof forms the ETOPS regulations.
FAA was the first to approve ETOPS guidelines in 1985. It spelt out conditions that need to be fulfilled before the grant of 120 minutes diversion period, which is sufficient for direct transatlantic flights. As a result , ETOPS today forms the bulk of the transatlantic flights.
The U.S. Federal Aviation Administration gave the first ETOPS rating to Trans World Airlines for a Boeing 767 service between St. Louis and Frankfurt, allowing TWA to fly its aircraft up to 90 minutes away from the nearest airfield: this was later extended to 120 minutes after a federal evaluation of the airline's operating procedures.
In 1988, the FAA amended the ETOPS regulation to allow the extension to 180 minutes diversion period subject to stringent technical and operational qualifications. This allows 95% of the earth available to ETOPS flights. The first such flight was conducted in 1989. This set of regulations are subsequently adopted by the The Joint Aviation Authorities, ICAO and other aviation regulatory bodies worldwide.
In this manner 757 series, 767 series, some Boeing 737 series, the Airbus A300-600, A310 series, A320 series and the A330 series were approved for ETOPS operations. Sucess of ETOPS airplanes like 767 and 777 killed the intercontinental trijets forcing Boeing to terminate the MD-11 programme and ironically scale down the production of Boeing 747.
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Boeing 777-200ER |
The regulations allows an airliner to have 120-min ETOPS rating on its entry into service. 180-min is only possible after 1 year of trouble-free 120-min ETOPS experience. Boeing has convinced the FAA that it could deliver an airliner with 180-min ETOPS on its entry into service. This process is called Early ETOPS. Thus the Boeing 777 was the first aircraft to carry an ETOPS rating of 180-min at its introduction.
The Joint Aviation Authorities, however disagreed and the Boeing 777 was rated 120-min in Europe on its entry into service. European airlines operating the 777 must demonstrate 1 year of trouble-free 120-min ETOPS experience before obtaining 180-min ETOPS for the 777.
Private jets are excempted from ETOPS by the FAA, but are subject to the 60-minute rule in the JAA's jurisdiction. Several commercial airline routes (mostly across the South Pacific Ocean) are still off-limits to twinjets because of ETOPS regulations.ETOPS exclusions