Blog

« Back to Blog List
blog image

April 18, 2018

Southwest Airlines engine explosion – Why it could happen again

by: Mary F. Schiavo

When a Southwest Airlines jet experienced an uncontained engine failure over Pennsylvania Tuesday, sending shrapnel into the passenger cabin, causing the plane to depressurize and creating what passengers have described as “extreme turbulence,” it was not a good day for aviation safety, or for those passengers. 

For the first time in almost a decade, a passenger died on board a U.S. commercial flight. 

I applaud the pilots of Southwest flight 1380 for their remarkable flying skills in an incredibly stressful situation and landing the plane safely.

And though the National Transportation Safety Board is still investigating the catastrophic event – an investigation that we will follow closely – we already have some very good clues about what occurred.

But the more important question is not what occurred – but why.

Though this engine loss was certainly unexpected to those on board, it was not entirely unanticipated to those in the industry. On Aug. 27, 2016, Southwest had experienced a very similar catastrophic engine failure of this type, which prompted an investigation by the NTSB, a service bulletin by the engine manufacturer, CFM International, and a proposed Airworthiness Directive by the Federal Aviation Administration.

Every major aviation accident is investigated by the NTSB, and Tuesday’s engine explosion is no different. But FAA officials and Southwest executives will have some tough questions to answer about why inspections of the engine fan blades – as recommended by the NTSB, the engine manufacturer, CFM, and included in a proposed FAA Airworthiness Directive dated August 25, 2017 – were not carried out.

Almost a year ago, CFM issued a service bulletin warning of the known problem with a very specific engine and its fan blades. In that June 13, 2017 service bulletin, it recommended an ultrasonic inspection on fan blades with certain serial numbers, and it further recommended that the inspections be carried out “as soon as possible, and not later than September 24, 2017 for engines that have accumulated more than 15,000 Flight Cycles since last shop visit at the date of March 24, 2017.” 

But service bulletins are not law. Though important and life-saving, they are mere requests, with reasoning and scientific rationale behind them.

What does become law, eventually, are FAA Airworthiness Directives. On Aug. 25, 2017, the FAA proposed an Airworthiness Directive to address this very specific, known problem. The FAA explained, “This proposed AD was prompted by a report of an in-flight fan blade failure and uncontained forward release of debris on a CFM56– 7B turbofan engine.” Yes, the NTSB preliminary report that was issued in September 2016 after the previous Southwest explosion. 

As with many proposed Airworthiness Directives, there is a period during which companies (and the public) can comment on the language in the rule, how they would be affected, and whether any modification of the rule is warranted. Those comments are then considered, and a final rule is published.

Unless that doesn’t happen.

The last day for comment on the rule that would have required mandatory inspections was Oct. 10, 2017. And on that same day, representatives from United Airlines, American Airlines, Delta Air Lines, Alaska Airlines and Southwest Airlines all submitted comments.

I’ll summarize Southwest’s comments, but to read them firsthand, they are available on the Federal Register.

Southwest complained about time and money.

Southwest complained that a 12-month compliance period to carry out the inspections was too short, and said it needed 18 months to complete the inspections. 

Southwest further complained that the Cost of Compliance estimated in the proposed rule was “vastly understated,” for an interesting reason. Despite that CFM fan blades have identifying serial numbers on them, Southwest points out that “no requirement exists to track fan blade part numbers, serial numbers or positions,” so Southwest must inspect 100 percent of its fleet. (American Airlines also admits in its comments that it routinely repositions fan blades without tracking, creating a similar conundrum. Incidentally, American asked for 20 months to complete inspections.)

But this Airworthiness Directive never became law. So airlines were not required to finish, or even start inspections at any given time. It is therefore possible that there are many more of these engines on planes flying today that exhibit metal fatigue, cracks or compromised fan blades.

Following yesterday’s tragedy, Southwest says it will carry out inspections on its fleet within 30 days. It’s a sad state of affairs when it takes the loss of life for meaningful action to take place, whether by market pressures or government mandates. The FAA has said nothing about its failure to timely act.

But waiting for a loss of life to force you to do what you know is right, is simply wrong. The FAA and U.S. airlines cannot brag that we have had the best commercial aviation safety record in decades if we don’t follow those words with actions. There is no excusing inaction in the face of a known problem. We owe it to the traveling public.