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Until recently, two-engine airliners were restricted to routes that put them within 180 minutes of an alternate in case of an engine failure. But Boeing and ALPA are pushing hard to increase this limit to 240 minutes to allow aging four-engine 747s to be replaced with long-range two-engine 777s, while Airbus and the Allied Pilots Association are arguing against such a move. Caught in the crossfire, the FAA has provisionally increased the limit to 207 minutes while it mulls over a permanent rule change. Ken Cubbin reviews the arguments on both sides of this debate.

SafetyExtended-Range Twin-Engine Operations (ETOPS) is a rating granted to airlines by international aviation regulatory authorities that allows those airlines to operate applicable two-engine aircraft over routes where the time to reach a suitable diversion airport in the case of an engine failure is greater than 60 minutes. Up until recently, according to strict compliance conditions, airlines could obtain ETOPS approvals of up to 180 minutes. However, recently the Federal Aviation Administration (FAA) has extended this approval by 15%, to 207 minutes, on a provisional basis; there is little doubt in the author's mind, that as long as nothing unforeseen occurs in the next year or two, FAA approval for ETOPS extension to 240 minutes is a matter of course.

Boeing 777Much of the impetus to extend ETOPS to 240 minutes is being led by Boeing, which plans to develop the Boeing 777 series aircraft into a viable replacement for aging Boeing 747-100 and 200 series aircraft. Proponents of extending ETOPS to 240 minutes include powerful forces within the aviation industry, such as the ATA (Air Transport Association) and ALPA (Air Line Pilots Association). However, other forces within the aviation industry, namely Airbus Industrie and the APA (Allied Pilots Association), remain unconvinced that operating two-engine aircraft on certain routes, such as those in the North Pacific, would maintain the excellent safety record that ETOPS aircraft have achieved over the last ten years. Dissenters claim that ETOPS extension by the FAA has become an ad hoc procedure that effectively regulates via policy letters and draft advisory material rather than a public notice, comment and rule-making process. It is time, they say, to pause and take a long look at all long-range aircraft safety and develop a consensus on improvements that may need to be regulated on an international basis.

Airbus considers that ETOPS operation in the North Pacific during cold winter months is far different to ETOPS operation in the Atlantic region and airframe/engine combinations have not been tested under these conditions.

Arguments for ETOPS extension

Since 1989, when ETOPS was extended to 180 minutes, two-engine long-range aircraft, such as the Boeing 767 and A330, have proved that modern, high-bypass turbofan engines are reliable and increasingly less likely to suffer an in-flight failure. In fact, proponents of ETOPS extension to 240 minutes say that simply as a function of having fewer engines to fail, two-engine aircraft are less likely to require an in-flight diversion than a three-engine or four-engine aircraft. Therefore, the extension of ETOPS to 240 minutes is based on improved technology, a proven track record of engine and airframe combinations and is the next logical step in the evolution of aviation.

Stringent operational and maintenance requirements placed on two-engine, ETOPS aircraft operators by international aviation regulatory authorities and extra safety precautions, such as additional fire suppression, make two-engine aircraft inherently safer than three-engine and four-engine aircraft. Therefore, rather than deteriorating, safety levels for the traveling public should be enhanced when older technology aircraft are gradually replaced by long-range two-engine aircraft. Additionally, because modern, two-engine aircraft, such as the Boeing 777, are more economical to operate than three-engine or four-engine aircraft, the traveling public will benefit from the containment and possible reduction in air fares. The interim measure of allowing a 15% increase on the 180 minutes ETOPS restriction to 207 minutes on an ‘as needed’ basis will prove that extending ETOPS to 240 minutes in the near future will not degrade safety.

Arguments against ETOPS extension

Statistically, it is true that a two-engine long-range aircraft has a lower likelihood of an in-flight diversion due to an engine failure than a three-engine or four-engine aircraft equipped with similar technology-based engines. However, if an engine failure occurs at the worst possible time – that is when the aircraft is farthest away from an emergency airport where a safe landing can be made – then there is an extra safety margin afforded by having more than one engine left operating. For example, a Boeing 747 or MD-11 can lose two engines and still remain airborne. In contrast, in the same circumstances, a Boeing 777 would have to fly to the diversion airport on one engine. Flying up to 240 minutes on one engine to an emergency airport in most cases would be safe; however, there is little doubt that a three-engine or four-engine aircraft offers a higher redundancy safety factor under this worst-case scenario.

Another factor that is problematic for all long-distance aircraft is volcanic ash cloud encounters. In the last 20 years there have been over 80 reports of aircraft entering volcanic ash clouds. For example, in 1989, a Boeing 747-400 entered a volcanic ash cloud near Anchorage, Alaska, and suffered four engine failures. Although the crew managed to restart all engines and land safely at Anchorage, the aircraft suffered $80 million of damage and all four engines were subsequently changed. Some volcanic ash cloud encounters in the past have occurred in Indonesia, The Philippine Islands, Japan, Guatemala, Columbia, Chile, Alaska, Zaire, Russia and New Guinea. Despite improved advanced warnings, the number of volcanoes and their relation to air routes remains a threat to aviation. If an aircraft were to encounter a volcanic ash cloud and suffer engine damage as a consequence, then there would be a higher redundancy afforded by having three or four engines instead of two. That is, if two engines failed as a result of volcanic ash damage, then a three-engine or four-engine aircraft could still remain airborne.

A very serious problem for all advanced aircraft is the human-technology interface and resultant loss of pilot operating skills. In the author’s opinion, safety has also been eroded on advanced-technology aircraft by the increased workload placed on the two pilots in emergency situations due to the deletion of the flight engineer position. Disaster can occur when workloads are increased to the point where human error is more likely to occur. For example, if multiple or complex automated systems fail, if data from instruments are misread by pilots under duress or if checklists are mishandled during critical steps, then situations like the following description are possible.

In 1989, a Boeing 737-400 operated by British Midland crashed near the M1 motorway while on approach to East Midlands Airport. While the aircraft had been en route from London to Belfast, the number one engine suffered a series of severe compressor stalls after a fan blade had become detached. Airframe shuddering and smoke infusion into the cockpit occurred as a result of the engine damage. The two-pilot crew mistakenly identified which engine had suffered damage and shut down the number two engine which up until that time had been operating normally. A diversion was initiated to runway 27 at East Midlands Airport; however, the severely damaged number one engine gave out on approach. Hasty attempts to restart the number two engine failed and the aircraft subsequently crashed short of the airfield. This flight could have landed safely had the correct engine been identified and shut down; however, as this incident demonstrates, when problems occur the ensuing workload can stretch the limits of two crew members.

Crew fatigue and its effect on the safe operation of aircraft is a subject of study by agencies such as NASA. In most cases, a two-man crew can be scheduled to operate a flight where the flight time does not exceed nine hours. While this does not seem excessive, fatigue of crew members is cumulative and a crew that is on the tail end of a multi-day pattern might begin a flight already feeling tired. If a two-man crew scheduled flight departs under these circumstances, then judgment, reaction time and motor skills are going to be severely degraded. Such a condition has been mentioned as a possible influencing factor in the recent American Airlines MD-82 accident in Little Rock, Ark.

Serious safety issue, or just nit-picking?

Some economists argue that the point of diminishing returns is being approached in regard to improving airline safety. The public, they say, is expecting too much safety assurance from a transport means that is already astronomically safe by any standard. For example, the traveling public accepts the fact that approximately 42,000 people are killed in road accidents every year in the United States. Yet, if the same accident rate were applicable to the airline industry, that would be equivalent to approximately twelve 300-seat aircraft crashes a month with an ensuing total loss of life. Last year in the United States there were zero fatalities in an industry that experienced approximately 5 billion passenger enplanements in domestic operations alone.

A person has more chance of being killed in his or her own home than in an airline crash and yet demands for increased safety in airline travel continue. At some point the public will have to accept that a zero accident rate in the airline industry is unattainable and the risk factor involved with air travel is about as good as it is going to get. What they do not have to accept, however, is an erosion of existing safety levels purely as a function of airline and aircraft manufacturer economic interests. In the author’s opinion, extension of ETOPS to 240 minutes will seriously challenge existing safety levels of long-distance air travel.

Boeing and Airbus are divergent in their opinions once again. The obvious benefit for Boeing is the prospective large market for its Boeing 777X aircraft and the possible replacement of aging Boeing 747-100 and 200 series aircraft. In addition, ETOPS extension to 240 minutes would enable some emergency airports, such as Midway Island (used for an emergency airport in the Southern Pacific region) that are currently subsidized by Boeing, to be closed. However, such closures, if they occur, would seriously affect all long-distance flights, whether they be two-engine, three-engine or four-engine aircraft that currently use these airports as emergency diversion points. Boeing denies that the approved ETOPS extension to 207 minutes on a provisional basis will be used as justification for Midway Island and other emergency airport closures. However, future financing of emergency airports might be subject to debate among airlines, aircraft manufacturers and aviation industry regulators if they are to be kept operational.

Airbus has decided not to pursue a competing aircraft to the Boeing 777X other than the A340; therefore, both of these companies have a vested interest in the extension or containment of the existing ETOPS limit of 180 minutes. Combined with Airbus Industrie’s possible development of the A3XX and Boeing’s contention that a market will not exist for VLTA (Very Large Transport Aircraft), the future of these companies will depend largely on which one of them is correct in its estimation of industry developments. Therefore, the arguments for and against ETOPS extension to 240 minutes appears to be largely based on economic interests rather than reality-based issues.

In an era when airlines, aircraft manufacturers and aviation regulatory authorities profess to being focused on reducing airline accidents by 50% in the next ten years, it seems odd that the impetus to extend ETOPS to 240 minutes is gathering steam without unanimous support within the industry. This contentious issue is one that will be profound in its effect on the future of commercial aviation. One can only hope that human lives are not lost in proving that operating two-man crew, two-engine aircraft over distances that require ETOPS of 240 minutes is a viable option. However, the author is left wondering, why the hurry?