Inspections of Aircraft Engines Under a Microscope Following Southwest Accident

Boeing 737 cockpit

By Paul Riegler on 19 April 2018
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Is a routine visual inspection of an engine enough?

After an engine on a Southwest Airlines Boeing 737 broke apart midflight on Tuesday, killing one person sitting in a window seat near the engine, the answer may be “no.”

That aircraft’s engine had been visually inspected on Sunday, and no problems were noted.

The accident was the first passenger fatality resulting from an accident on a U.S. airline in nine years and the first in Southwest’s history.

As Southwest’s CEO, Gary Kelly, noted during a press conference concerning the accident, “the 737 is the workhorse of the airline industry.”

The fatal accident rate for early Boeing 737s such as the 100 and 200 models was 0.89 for every million departures.  That number fell to 0.25 for the so-called Classic versions – namely the 300, 400, and 500 variants – and fell again to 0.09 for the Next Generation models such as the 600, 700, 800, and 900.  The aircraft involved in Tuesday’s accident was a 700.

These rates compare favorably to those of other aircraft. The Airbus A310, for example, has a fatal accident rate of 1.85 per million departures. The Boeing 777, which is a contemporary of the Next Generation 737s, has a fatal accident rate of 0.2.

With minor exceptions, only brand new aircraft such as the Boeing 787 Dreamliner, the Airbus A350, and the Bombardier C-Series have a fatal accident rate of 0 and the 737 Next Generation’s rate of 0.09 is only bested by the Embraer 170/175/190 series with a rating of 0.07, before accounting for the new aircraft.

The accident came as a shock although it closely resembled a 2016 incident where another Southwest 737 blew an engine as it flew from New Orleans to Orlando that forced an emergency landing, although there were no fatalities. The National Transportation Safety Board found that a fan blade had broken off, apparently due to metal fatigue.

While the plane involved in Tuesday’s incident began flying in July 2000, its engines had undergone regularly scheduled maintenance.  Following the incident in 2016, the engine manufacturer, CFM, a joint venture of General Electric Co. and France’s Safran SA, issued a service bulletin to its customers recommending an ultrasonic inspection of certain fan blades and, if they were to fail the inspection, the replacement of those parts.  It isn’t clear whether the specific 737 involved in the event on Tuesday was inspected as the Federal Aviation Administration never finalized an Airworthiness Directive that would have made such inspections mandatory.

Southwest sought more time to conduct the inspections recommended by CFM, as did other airlines, voicing concern over the sheer number of engines that would require inspection.

Meanwhile, several airlines, including Southwest, said they plan to inspect the fan blades in their engines, a move that they hope will avert future such incidents from taking place.  The FAA said it plans to make such inspections mandatory and will issue an order within the next two weeks.

(Photo: Accura Media Group)

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