ETOPS – Extended-range Twin-engine Operational Performance Standards

ETOPS

ETOPS is an acronym for Extended-range Twin-engine Operational Performance Standards, an International Civil Aviation Organization (ICAO) rule permitting twin-engine commercial air transporters to fly routes that, at some points, are farther than a distance of 60 minutes’ flying time from an emergency or diversion airport with one engine inoperative.

This rule allows twin-engine airliners—such as the Airbus A300, A310, A32X, A330 and A350 families, and theBoeing 737, 757, 767, 777 and 787—to fly long-distance routes that were previously off-limits to twin-engine aircraft. ETOPS operation has no direct correlation to water or distance over water. It refers to single-engine flight times between diversion airfields—regardless as to whether such fields are separated by water or land.

 

 

Early ETOPS experience

The FAA and the ICAO concluded that it is safe for a properly designed twin-engined airliner to conduct intercontinental transoceanic flights. The guidelines issued form the ETOPS regulations.

The FAA was the first to approve ETOPS guidelines in 1985. It spelled out conditions that need to be fulfilled for a grant of 120 minutes’ diversion period, which is sufficient for direct transatlantic flights. Today, ETOPS forms the bulk of transatlantic flights.

The FAA gave the first ETOPS rating in May 1985 to TWA for the B767 service between St. Louis andFrankfurt, 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 extensions

In 1988, the FAA amended the ETOPS regulation to allow the extension to a 180-minute diversion period subject to stringent technical and operational qualifications. This made 95% of the Earth’s surface available to ETOPS flights. The first such flight was conducted in 1989. This set of regulations was subsequently adopted by the Joint Aviation Authorities (JAA), ICAO and other regulatory bodies.

In this manner the B737, 757 and 767 series and the Airbus A300-600, 310, 320 and 330 series were approved for ETOPS operations. The success of ETOPS aircraft like 767 and 777 killed the intercontinental trijets. This ultimately led Boeing to end the MD-11 program a few years after Boeing’s merger with McDonnell Douglas, as well as to scale down the production of its own Boeing 747.

The cornerstone of the ETOPS approach are the statistics that show that the turbine itself is an inherently reliable component, and it is the engine ancillaries that have a lower reliability rating. Therefore an engine for a modern twin jet airliner has twin sets of all ancillaries mounted in the engine, which gives the required reliability rating.

The North Atlantic airways are the most heavily used oceanic routes in the world. Most North Atlantic airways are covered by ETOPS 120-minute rules, removing the necessity of using 180-minute rules. However, many of the North Atlantic diversion airports, especially those in Iceland and Greenland, are subject to adverse weather conditions making them unavailable for use. As the 180-minute rule is the upper limit, the JAA has given 15% extension to the 120-minute rules to deal with such contingencies, giving the ETOPS-138min, thereby allowing ETOPS flights with such airports closed.

ETOPS240 and beyond are now permitted[1] on a case-by-case basis, with regulatory bodies in nations ranging from the USA, to Australia, to New Zealand adopting said regulatory extension. Authority is only granted to operators of two-engine airplanes between specific city pairs. The certificate holder must have been operating at 180 minute or greater ETOPS authority for at least 24 consecutive months, of which at least 12 consecutive months must be at 240-minute ETOPS authority with the airplane-engine combination in the application.

 

 

Early ETOPS

The regulations allow an airliner to have ETOPS-120 rating on its entry into service. ETOPS-180 is only possible after 1 year of trouble-free 120-minute ETOPS experience. Boeing has convinced the FAA that it could deliver an airliner with ETOPS-180 on its entry into service. This process is called Early ETOPS. Thus the B777 was the first aircraft to carry an ETOPS rating of 180 minutes at its introduction.

The JAA, however disagreed and the Boeing 777 was rated ETOPS-120 in Europe on its entry into service. European airlines operating the 777 must demonstrate one year of trouble-free 120-minutes ETOPS experience before obtaining 180-minutes ETOPS for the 777.

 

 

ETOPS exclusions

Private jets are exempted from ETOPS by the FAA, but are subject to the ETOPS 120-minute rule in JAA’s jurisdiction. Several commercial airline routes are still off-limits to twinjets because of ETOPS regulations. There are routes traversing the South Pacific (e.g. Auckland,New Zealand – Santiago, Chile), Southern Indian Ocean (e.g. Perth, Western Australia -Johannesburg, South Africa) and Antarctica.

 

 

Beyond ETOPS-180

Effective February 15, 2007, the FAA ruled that US-registered twin-engined airplane operators can fly over most of the world other than the South Polar Region, a small section in the South Pacific, and the North Polar area under certain winter weather conditions provided that the inflight shutdown rate is 1 in 100,000 engine hours. This limit is more stringent than ETOPS-180 (2 in 100,000 engine hours).

The qualified aircraft must have appropriate fire-suppression systems, adequate oxygen supplies for crew and passengers (to continue high altitude flight) in the event of depressurisation, and automated defibrillators. Weather reporting, training, and diversion accommodation requirements remain unchanged. Since aircraft occasionally divert for non-engine mechanical problems or passenger medical emergencies, the rule requires that airplane systems be able to support lengthy diversions in remote and sometimes harsh environments. The rules do not apply to 3- or 4-engined cargo aircraft or twinjets freed from ETOPS constraints.

EASA distinguishes between twin-engine (ETOPS) and aircraft with 3 or 4 engines. Rules governing such aircraft (3 or 4 engines) are covered under LROPS rules. LROPS would demand similar rules with regard to emergency oxygen and fire-suppression. EASA is expected to release rules for ETOPS and LROPS in 2008.

 

 

ETOPS ratings

The following ratings are awarded under current regulations according to the capability of the airline:

  • ETOPS-75
  • ETOPS-90
  • ETOPS-120/138
  • ETOPS-180/207

However, ratings for ETOPS type approval are fewer. They are:

  • ETOPS-90, which keeps pre-ETOPS Airbus A300B4 legally operating under current rules
  • ETOPS-120/138
  • ETOPS-180/207, which covers 95% of the Earth’s surface.

 

 

Approval for ETOPS

ETOPS approval is a two-step process. Firstly: the airframe and engine combination must satisfy the basic ETOPS requirements during its type certification. This is called ETOPS type approval. Such tests may include shutting down an engine and flying the remaining engine during the complete diversion time. Often such tests are performed in the middle of the oceans. It must be demonstrated that, during the diversion flight, the flight crew is not unduly burdened by extra workload due to the lost engine and that the probability of the remaining engine failing is extremely remote. For example, if an aircraft is rated for ETOPS-180, it means that it should be able to fly with full load and just one engine for 3 hours.

Secondly: An operator who conducts ETOPS flights must satisfy his own country’s aviation regulators about his ability to conduct ETOPS flights. This is called ETOPS operational certification and involves compliance with additional special engineering and flight crew procedures on top of the normal engineering and flight procedures. Pilots and engineering staff must be qualified and trained for ETOPS. An airline with extensive experience operating long distance flights may be awarded ETOPS operational approval immediately, others may need to demonstrate ability through a series of ETOPS proving flights.

Regulators closely watch the ETOPS performance of both type certificate holders and their affiliated airlines. Any technical incidents during an ETOPS flight must be recorded. From the data collected , the reliability of the particular airframe-engine combination is measured and statistics published. The figures must be within limits of type certifications. Of course, the figures required for ETOPS-180 will always be more stringent than ETOPS-120. Unsatisfactory figures would lead to a downgrade, or worse, suspension of ETOPS capabilities either for the type certificate holder or the airline.

 

 

References

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