1990-09-01

Continuing the Etops Debate A Philosophy of Safety Overview 902021

Five years ago, a new experiment in passenger air transportation for Atlantic Ocean crossings was introduced. It was given the acronym known as ETOPS and involves the development of passenger aircraft having only two-engines utilized for flights over such critical routes.
The essence of the concern generated in this study is summarized by the safety analysis of Dr. Robert Besco, who states, “ETOPS is troublesome because the failure of only one system on an aircraft [In this case an engine] should not cause that aircraft to have to operate under emergency conditions.”
Previously, a major cornerstone of civil aviation safety was the concept of providing multiple engine redundancy with a minimum of three-engines required for such critical flights. The accepted safety premise was that many unfavorable factors such as engine failures could jeopardize such flights and therefore the fail-safe method of providing three- or four-engine redundancy for these transports was prudent as well as comforting. Three- and four- engine transports are considered more safety efficient than two-engine transports or a possible one-engine transport of the future. Corporate, military and private flights in two- and one-engine aircraft fly such routes; however, they are not obligated to provide the highest safety standards that are required and expected of civil aviation transport operators.
Formerly, two-engine transports were only permitted to fly over-land and over very short over-water segments primarily during domestic operations, and regulations still require that, when an engine fails, a landing must be made at the nearest suitable airport in point of time where a safe landing can be made. From over the United States and portions of Canada, this can often be accomplished in a relatively short time period of as little as thirty-minutes. Many emergency airfields are continuously available along such domestic routes.
Indeed, in 1983 when one of these new twin-engine transports suffered a failure of both engines (due to fuel starvation problems), the aircraft glided powerless to a safe landing at a nearby emergency airfield. Such emergency airfields do not exist over the vast oceanic and desolate land areas over which ETOPS aircraft now may operate. The requirements for such emergency airfields were warved for ETOPS flights and instead, the - Federal Aviation Administration (FAA) gave credit for better engine reliability. Now, instead of requiring immediate landings of such two-engine transports after an engine failure, it is permissible to fly as long as three hours or cover over one-thousand miles, based heavily on the statistical success of continued favorable operation of the remaining engine. Proponents argue that safety is not compromised when engine redundancy is reduced in the ETOPS concept and certainly a good oceanic-track record during the next several decades is essential in order to promote the idea as sound. However, many aviation safety specialists are not convinced and cite several problem areas. For instance, some two-dozen engine shut-downs and over onehundred other serious situations have occurred where the ETOPS aircraft operated under emergency conditions or otherwise diverted to other destinations. In addition, some close calls have occurred, sirch as a one-engine diversion to an emergency airfield where the weather conditions had deteriorated to less than safe landing limits by the time the aircraft arrived. This was a very dangerous condition and one in which ETOPS aircraft are more vulnerable.
During the summer of 1989 one trans-atlantic air-carrier had its ETOPS authority severely reduced due to the airlines' development of too many engine failures and related maintenance problems.
Thus, aviation specialists continue to raise many and varied questions regarding ETOPS safety issues. It is unclear why these new generation engines with improved reliability were not initially fitfed onto new three- and four-engine air transport designs, thereby achieving the added safety benefits of both increased engine reliability as well as better engine redundancy. Other questions are detailed in the following text.
This research paper contains historical as well as current information regarding the growing world trend in the use of two-engine civil air transports over vast desolate land areas and long oceanic routes.

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