The NTSB issued the recommendation as part of its investigation into Southwest Flight 1380 last year. An engine failure killed one passenger.
- Boeing should redesign the cowling that covers the engines on its 737 NG aircraft, the National Transportation Safety Board said Tuesday.
- The NTSB report closed the investigation into Southwest Flight 1380, which suffered an in-flight engine failure in April 2018. The engine came apart, killing a passenger when debris struck the plane's body.
- The redesign and replacement could represent a significant cost to Boeing. The crash and the report is unrelated to the 737 Max scandal.
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Federal transportation safety investigators said that Boeing should redesign the engine housing on its 737 New Generation (NG) planes, following a deadly catastrophe on Southwest flight 1380 in April of last year.
One passenger died after an engine fan blade broke on the Southwest flight from New York's La Guardia Airport to Dallas Love Field. The fan caused the engine housing to break apart — a piece of debris hit the body of the 737-700 and broke a window, causing the cabin to rapidly lose pressure.
Passenger Jennifer Riordan was killed after she was partially sucked out the window, and eight other passengers had minor injuries. The plane made an emergency landing in Philadelphia.
In a report ending a 19 month investigation into the crash, the National Transportation Safety Board (NTSB) called on Boeing to redesign the engine cowling — the removable cover of the engine — to better contain debris if an internal piece breaks in the future.
There are about 7,000 737 NG planes that have been delivered to customers since the plane type was introduced in the late-1990s. The NTSB called on Boeing and the plane's operators to retrofit all existing planes with the newly designed part.
Notably, however, the board did not fault the original design process of the engine.
It instead focused on reconsidering the process of designing the engine to withstand internal impacts during "fan blade out," or FBO, failures, since the fan blade broke and struck the nacelle in way that was different than Boeing and the engine maker, CFM International, expected.
Engines are designed to contain parts in event of a failure. While it did so during the Southwest flight, the engine cowling broke off as the fan blade rattled against the engine.
The NTSB did not recommend grounding the planes, and noted that airlines are inspecting the fan blades of similar CFM56-7B engines more frequently following the accident.
The board also noted that there have only been two reported failures of the engine type, despite there being 14,600 CFM56-7B engines in service, with a total of 365,000 fan blades and 400 million flight cycles over 20 years.
The recommendations are not immediately binding unless the Federal Aviation Administration (FAA) implements them as directives.
However, a spokesperson for Boeing told the Dallas Morning News that the company was already working on "enhancements to the 737 NG cowls."
"Boeing is committed to working closely with the FAA, engine manufacturers, and industry stakeholders to implement enhancements that address the NTSB's safety recommendations," the spokesperson said.
The report comes as Boeing works with the FAA and airlines to determine an inspection and repair schedule to find and fix cracks in the "pickle fork" on 737 NG planes. The pickle fork, a section that reinforces where the planes' wing meets the body, has been found to have developed cracks on 50 planes globally with 20,000 flight hours or more — fewer hours than expected before cracks would develop.
Boeing, regulators, and airlines maintain that there is no safety risk involved. The planes are designed to fly even with damage to the pickle fork thanks to redundant safety features, according to Stephen Fankhauser, a Swinburne University of Technology aviation expert in Australia who was cited by AFP.
The pickle fork issue on the 737 NGs is unrelated to the ongoing crisis surrounding the 737 Max, the newer generation of the workhorse jet.
The Boeing 737 NG — which includes the 737-600, -700, -800, and -900 variants — is a backbone of commercial fleets around the world, with more than 7,000 sold.