ETOPS
ETOPS (Extended Twin-engine OPerationS) is an acronymn for an International Civil Aviation Organization (ICAO) rule permitting newer twin-engined commercial air transports to fly routes that, at some points, are further than a distance of 60 minutes flying time from an emergency or diversion airport. This definition allows twin-engined airliners—like Boeing 757, 767, 777 and Airbus A300, A320 series, A330—to fly routes long distances (especially over water) that were previously off-limits to twin-engined aircraft. ETOPS is sometimes read (unofficially) as Engines Turn or Passengers Swim.
| Table of contents |
|
2 Early turbine engine experience 3 Early twin-engine high-bypass turbofan airliners 4 Early ETOPS experience 5 ETOPS extensions 6 Early ETOPS 7 ETOPS exclusions |
The first transatlantic crossing was in 1919, made by RAF pilots Alcock and Brown using a twin engined Vickers Vimy after a 16 hour flight. However, due to the unreliability of piston engines in those days (see internal combustion engine), long distance flight using twin engines was considered risky at best. A flagship of the piston era, the 4-engined Lockheed Constellation airliner, was regarded as so unreliable, that it was jokingly dubbed "the most reliable 3-engined airplane flying"!
The FAA in 1953, having recognised piston engine limitations, introduced the '60-minute rule' for 2- and 3-engine aircraft. This rule states that the flight path of these types of airplanes shall not be any further than a distance of 60 minutes flying time from any airport. This forced these airplanes, on certain routes, to fly a dogleg path in order to stay within regulations; they were totally excluded from certain routes due to lack of 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 routes. This opened 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
|
Airbus A300 , the precursor for ETOPS.
|
Outside the USA, other countries follow ICAO regulations, which allowed for a 90 minutes diversion time. This fact was exploited by Airbus, launching 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.
|
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.
|
|
ETOPS permitted area of operation. Light blue and lighter shade of beige are areas covered under ETOPS-120min rules. Darker shades of blue and gray are areas covered under ETOPS-180min rules. Dark blue and dark gray represents areas that are off-limits to ETOPS flights.
|
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 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. Success 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.
North Atlantic airways are the most heavily utilized oceanic routes in the world. Most are conveniently covered by ETOPS-120min rules. It is not necessary to utilize 180-min rules for such routes. However, many of the North Atlantic diversion airports, especially the Icelandic and Greenland ones, are subjected to adverse weather conditions making them unavailable for use under the 120-min rules. As the 180-min rules is the upper limit, the JAA, has given 15% extension to the 120-min rules to deal with such contigencies, giving the ETOPS-138min thereby allowing ETOPS flights with such airports closed.
In the North Pacific, ETOPS-180min is satisfied by the availability of airports in the Aleutians Islands and Midway Atoll. As the Aleutians airports are prone to adverse weather conditions and volcanic activities, Boeing subsidised Midway Atoll diversion airport to enable Boeing 777, to fly the North Pacific routes. After petition from Boeing and United Airlines, in 2001, the FAA allowed the 15% extension to the 180-min rules bringing it to 207-min. The approval is granted only to Boeing 777. This approval is granted only if Northern Pacific enroute diversion airportss are closed.
However, the JAA differed because it was argued that ETOPS-180min is already the upper limit and such extension may compromise safety as the airliners are only certificated for at most, the ETOPS-180min rating. This difference remains until today.
|
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 are still off-limits to twinjets because of ETOPS regulations. They are routes travessing the South Pacific, Southern Indian Ocean such as Perth, Australia to Johannesburg, South Africa and the Antarctica such as Auckland, New Zealand to Buenos Aires, Argentina.ETOPS exclusions