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Thread: Southwest 737 Engine Failure - NTSB Find Metal Fatigue

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    Lightbulb Southwest 737 Engine Failure - NTSB Find Metal Fatigue


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    Default Re: Southwest 737 Engine Failure - NTSB Find Metal Fatigue

    ATW Online; Wednesday 18 April 2018
    NTSB: Investigators find metal fatigue in Southwest 737 engine failure

    US National Transportation Safety Board (NTSB) investigators found evidence of metal fatigue in the left engine of the Southwest Airlines Boeing 737-700 that made an emergency landing at Philadelphia International Airport on April 17 after the pilots initially reported an engine fire, then clarified that there was no fire but that engine parts were missing.

    A woman died after an apparent engine explosion blew out a window and caused the cabin to depressurize, nearly pulling her from the aircraft, according to media reports. The passenger fatality was the first on a U.S. airline since 2009.

    There were 144 passengers and five crew aboard for Southwest flight 1380, which had departed New York La Guardia Airport for Dallas Love Field. Southwest initially said the flight carried 143 passengers.

    At a 9 p.m. briefing at the airport the day of the incident, NTSB chairman Robert Sumwalt said investigators immediately focused on a missing fan blade in the damaged CFM56-7B turbofan engine. The number 13 fan blade, one of 24 fan blades that draw air into the engine, was broken at the point where it attached to the hub. “Our preliminary examination of this was that there is evidence of metal fatigue where the blade separated,” he told reporters.

    The engine cowling was found in Bernville, Pennsylvania, about 70 miles northwest of the airport.

    Sumwalt said the NTSB wants to determine if the affected engine part is subject to a pending FAA airworthiness directive (AD) for certain CFM56-7B engines that would require ultrasonic inspections of certain fan blades. The agency proposed the AD after a Southwest 737 experienced a fan blade failure while flying from New Orleans to Orlando in August 2016. The flight crew landed the aircraft safely at Pensacola International Airport.

    In June 2017, engine manufacturer CFM International issued a revised service bulletin that recommended one-time ultrasonic inspection of high-time fan blades “as soon as possible” on CFM56-7B engines.

    By: Bill Carer
    NS Comment: Mercifully the engine cowling didn't cause ground fatalities.
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    Default Re: Southwest 737 Engine Failure - NTSB Find Metal Fatigue


    Engine cowling from CFM56-7B engine that failed on Southwest Airlines flight 1380. Courtesy NTSB
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    Default Re: Southwest 737 Engine Failure - NTSB Find Metal Fatigue

    ATW Online; Thursday 19 April 2018
    FAA to issue CFM56 engine directive after Southwest incident

    FAA will issue an airworthiness directive (AD) in the next two weeks requiring inspections of certain CFM56-7B turbofan engines, the US agency announced one day after the Southwest Airlines Boeing 737-700 engine failure.

    “The directive will require an ultrasonic inspection of fan blades when they reach a certain number of takeoffs and landings. Any blades that fail the inspection will have to be replaced,” FAA said in a statement released on the evening of April 18.

    US National Transportation Safety Board (NTSB) investigators responding to the Philadelphia airport immediately focused on a missing fan blade in the damaged engine. The number 13 fan blade - one of 24 titanium alloy fan blades - had broken at the point where it attached to the disk hub, where there was evidence of fatigue cracking.

    At an April 18 briefing, NTSB chairman Robert Sumwalt said the fan blade separated in two places. “It also fractured roughly halfway through, but it appears the fatigue fracture was the initiating event that later caused that secondary failure,” he told reporters.

    The engine cowling was found in Bernville, Pennsylvania, about 70 miles northwest of the airport. Air traffic control primary radar detected additional debris falling through the atmosphere, and additional pieces of engine cowling later were recovered.

    Last August, FAA released a proposed AD that would require engines with more than 15,000 cycles-in-service since their last engine shop visit to undergo ultrasonic inspection of certain fan blades within six months of the rule’s effective date. The European Aviation Safety Agency (EASA) issued a comparable AD in March that became effective April 2. It requires ultrasonic inspection of each affected fan blade within nine months.

    By: Bill Carer
    NS Comment: More OOPs for USIs.
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    Default Re: Southwest 737 Engine Failure - NTSB Find Metal Fatigue

    Guess by the nine month limit, an increase of three months added to the original proposed AD limit, there seems to be little to worry about!
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    Default Re: Southwest 737 Engine Failure - NTSB Find Metal Fatigue

    Hopefully not all Powerplant Engineers are waiting to call this out at 9 months. The EASA AD 2018-0071 gives credit to affected Fan Blades which have been satisfactorily inspected by Eddy Current, ESM Task 72-21-01-200-001 Rev 55 or later, or the instructions of CFM56-7B SB 72-1019 R0 dated 24 March 2017, or R1 dated 13 June 2017.

    Operators under the FAA will not be bothered by the EASA AD, but the NPRM from last August has given them a chance to submit comments and/or plan for compliance in accordance with the Ref. Publications.
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    Default Re: Southwest 737 Engine Failure - NTSB Find Metal Fatigue

    ATW Online; Friday 20 April 2018
    FAA, EASA issue emergency directives for CFM56-7B inspections

    The FAA and European Aviation Safety Agency (EASA) late April 20 issued emergency airworthiness directives (AD) calling for inspections of fan blades on CFM56-7B engines that power Boeing 737NGs.

    The emergency ADs come three days after a CFM56-7B-powered Southwest Airlines 737-700 carrying 144 passengers and five crew made an emergency landing at Philadelphia International Airport after experiencing an apparent left-engine explosion. One passenger died in the incident.

    The directives follow a service bulletin (CFM56-7B SB 72-1033) engine manufacturer CFM International also issued April 20, recommending that fleet operators perform ultrasonic fan-blade inspections “within the next 20 days” on high-time CFM56-7B turbofans. The SB recommends inspections at different thresholds for all blades, with the highest-time blades - those with 30,000 or more cycles - needing inspections immediately. CFM also recommends repetitive inspections.

    EASA’s AD [AD 2018-0093-E] adopts the SB, while the FAA directive only mandates one-time inspections on the highest time blades. FAA plans to follow up with another directive that would cover the rest of the blade population and possibly require repetitive checks.

    FAA’s directive [EAD 2018-09-51] describes its requirement as “a one-time ultrasonic inspection (USI) of all 24 fan blade dovetail concave and convex sides to detect cracking” within 20 days.

    EASA’s directive supersedes an AD the agency released in March, which became effective on April 2 and was in response to an August 2016 Southwest 737-700 uncontained engine failure. “Since the AD was issued, a further failure of a fan blade of a CFM56-7B engine has been reported,” EASA said.

    The US National Transportation Safety Board (NTSB) initially found that one of the 24 titanium alloy fan blades in the engine in the April 17 Southwest incident had separated from the fan hub, where there was evidence of fatigue cracking. The safety board has said it is too early to say if the 2016 engine failure and the latest incident are directly related.

    CFM, the GE Aviation/Safran Aircraft Engines joint venture, said there are roughly 14,000 CFM56-7B engines in service. The fan-blade inspections recommended within 20 days would be for engines with more than 30,000 cycles since delivered new—each cycle consisting of an engine start, takeoff and landing, and full shut down. That affects about 681 engines worldwide, of which 150 have already been inspected, CFM said. Some 352 engines would be affected in the US, FAA said.

    CFM said it issued the recommendation in “close collaboration” with FAA, EASA, Boeing and CFM56-7B operators. CFM recommends inspections “by the end of August” for fan blades with 20,000 cycles, and inspections of all other fan blades when they reach 20,000 cycles. After the first inspection, the manufacturer recommends operators repeat the inspection every 3,000 cycles, which represents about two years in airline service.

    Inspections can be conducted on-wing with an ultrasonic probe along the surface of the fan blade and take about four hours per engine, CFM said.

    “About 60 customers worldwide operate engines within the cyclic thresholds of the new service bulletin,” CFM stated. “CFM partners GE and Safran Aircraft Engines have about 500 technicians directly involved to support customers and minimize operational disruption.”

    By: Bill Carer and Sean Broderick
    NS Comment: Ratcheted up for sharp-ish compliance.
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