DCA18MA142

NTSB accident investigation · Boeing 737 7H4 · Philadelphia, PA · April 17, 2018

Accident · FatalClass 1 · MajorFinal report
Date
April 17, 2018, 11:03 local (15:03 UTC)
Place
Philadelphia, PA
Injuries
1 fatal, 8 serious, 125 minor, 6 uninjured
Damage
Substantial damage
Phase of flight
Enroute
Aircraft
N772SWBoeing 737 7H4
Defining event
Enroute-climb to cruise: Powerplant sys/comp malf/fail
Weather
Visual (VMC) · Day
Status
Completed · report March 10, 2020
Report
Board-adopted at Board Meeting
Investigation class
Class 1
NTSB office
Major Investigations Division
Safety recommendations
Yes
FAA report
20180417024829A
Case key
97056

From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.

On this page

Probable cause

A low-cycle fatigue crack in the dovetail of fan blade No. 13, which resulted in the fan blade separating in flight and impacting the engine fan case at a location that was critical to the structural integrity and performance of the fan cowl structure. This impact led to the in-flight separation of fan cowl components, including the inboard fan cowl aft latch keeper, which struck the fuselage near a cabin window and caused the window to depart from the airplane, the cabin to rapidly depressurize, and the passenger fatality.

Findings · 5

NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings. Under each, the cases with the same finding.

Engine (turbine/turboprop): compressor sectionAircraft › Aircraft power plant · Fatigue/wear/corrosionBoeing 737-7H4: 2 casesAll aircraft: 53 casesProbable cause
Nacelles/pylons structure: nacelle/pylon misc structureAircraft › Aircraft structures · Damaged/degradedBoeing 737-7H4: 1 caseAll aircraft: 5 casesProbable cause
Windows-windshield system: passenger compartment windowsAircraft › Aircraft structures · Damaged/degradedBoeing 737-7H4: 1 caseAll aircraft: 2 casesProbable cause
Action: lack of actionPersonnel issues › Action/decision · Cabin crewBoeing 737-7H4: 2 casesAll aircraft: 792 cases

Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident. Under each, the cases with the same event anywhere in their sequence.

Analysis

The NTSB's full report is available at http://www.ntsb.gov/investigations/AccidentReports/Pages/AccidentReports.aspx. The Aircraft Accident Report number is NTSB/AAR-19/03. On April 17, 2018, about 1103 eastern daylight time, Southwest Airlines flight 1380, a Boeing 737-7H4, N772SW, experienced a left engine failure while climbing through flight level 320 en route to the flight's assigned cruise altitude. The flight had departed from LaGuardia Airport, Queens, New York, about 30 minutes earlier. As a result of the engine failure, the flight crew conducted an emergency descent and diverted to Philadelphia International Airport (PHL), Philadelphia, Pennsylvania. Portions of the left engine inlet and fan cowl separated from the airplane, and fragments from the inlet and fan cowl struck the left wing, the left-side fuselage, and the left horizontal stabilizer. One fan cowl fragment impacted the left-side fuselage near a cabin window, and the window departed the airplane, which resulted in a rapid depressurization. The airplane landed safely at PHL about 17 minutes after the engine failure occurred. Of the 144 passengers and 5 crewmembers aboard the airplane, 1 passenger received fatal injuries, and 8 passengers received minor injuries. The airplane was substantially damaged. The regularly scheduled domestic passenger flight was operating under the provisions of Title 14 Code of Federal Regulations Part 121 with a destination of Dallas Love Field, Dallas, Texas. The National Transportation Safety Board determines the probable cause(s) of this accident as follows: A low-cycle fatigue crack in the dovetail of fan blade No. 13, which resulted in the fan blade separating in flight and impacting the engine fan case at a location that was critical to the structural integrity and performance of the fan cowl structure. This impact led to the in-flight separation of fan cowl components, including the inboard fan cowl aft latch keeper, which struck the fuselage near a cabin window and caused the window to depart from the airplane, the cabin to rapidly depressurize, and the passenger fatality.

Factual narrative

The NTSB's full report is available at http://www.ntsb.gov/investigations/AccidentReports/Pages/AccidentReports.aspx. The Aircraft Accident Report number is NTSB/AAR-19/03. On April 17, 2018, about 1103 eastern daylight time, Southwest Airlines flight 1380, a Boeing 737-7H4, N772SW, experienced a left engine failure while climbing through flight level 320 en route to the flight's assigned cruise altitude. The flight had departed from LaGuardia Airport, Queens, New York, about 30 minutes earlier. As a result of the engine failure, the flight crew conducted an emergency descent and diverted to Philadelphia International Airport (PHL), Philadelphia, Pennsylvania. Portions of the left engine inlet and fan cowl separated from the airplane, and fragments from the inlet and fan cowl struck the left wing, the left-side fuselage, and the left horizontal stabilizer. One fan cowl fragment impacted the left-side fuselage near a cabin window, and the window departed the airplane, which resulted in a rapid depressurization. The airplane landed safely at PHL about 17 minutes after the engine failure occurred. Of the 144 passengers and 5 crewmembers aboard the airplane, 1 passenger received fatal injuries, and 8 passengers received minor injuries. The airplane was substantially damaged. The regularly scheduled domestic passenger flight was operating under the provisions of Title 14 Code of Federal Regulations Part 121 with a destination of Dallas Love Field, Dallas, Texas.

Aircraft

Registration
N772SW
Reported as
Boeing 737 7H4 (7H4)
Category
Airplane
Serial number
27880
Built
2000
Engines
CFM Intl. CFM56 SERIES, turbo fanCFM Intl. CFM56 SERIES, turbo fan
Damage
Substantial damage
Flight
Part 121
Operator
Southwest Airlines Co
Registered owner
Southwest Airlines Co
Airworthiness certificate
Standard, Transport
Departed
LGA · New York, NY
Destination
DAL · Dallas, TX
Flight plan
IFR
Airport
KPHL · Philadelphia, runway 27L, 12,000 × 200 ft

Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

Weather

Conditions
Visual (VMC) · Day

Docket · 53

The files NTSB released with the investigation on November 14, 2018, on NTSB’s docket system: statements, records, photos and specialists’ reports. 197 MB in all.

1-A Order of HearingItem 1 · .PDF · 159 KB1-B Designation of Chairman Board of InquiryItem 2 · .PDF · 187 KB1-C Designation of Hearing OfficerItem 3 · .PDF · 52 KB1-D Designation of Parties to the HearingItem 4 · .PDF · 168 KB1-E Notice of Investigative HearingItem 5 · .PDF · 47 KB1-F Statement of PurposeItem 6 · .PDF · 140 KB1-G Witness ListItem 7 · .PDF · 70 KB1-H Investigative Hearing Witness Professional BiographiesItem 8 · .PDF · 162 KB2-A Operational Factors Group Chairman's Factual ReportItem 9 · .PDF · 936 KB2-B Operational Factors Group Chairman's Factual Report Attachment 1Item 10 · .PDF · 196 KB2-C Operational Factors Group Chairman's Factual Report Attachment 2Item 11 · .PDF · 290 KB2-D Operational Factors Group Chairman's Factual Report Attachment 3Item 12 · .PDF · 177 KB2-E Operational Factors Group Chairman's Factual Report Attachment 4Item 13 · .PDF · 135 KB2-F Operational Factors Group Chairman's Factual Report Attachment 5Item 14 · .PDF · 174 KB2-G Operational Factors Group Chairman's Factual Report Attachment 6Item 15 · .PDF · 593 KB2-H Operational Factors Group Chairman's Factual Report Attachment 7Item 16 · .PDF · 169 KB3-A Air Traffic Control Specialist ReportItem 17 · .PDF · 198 KB3-B Air Traffic Control Specialist Report - Attachment 1Item 18 · .PDF · 1.7 MB3-L Air Traffic Control - Radar Data Multiple Sensors in Excel FormatItem 19 · XLSX · 238 KB3-M Air Traffic Control - 84TH RADES Primary Radar Data with Height Finder in Excel FormatItem 20 · XLSX · 17 KB3-N Air Traffic Control - FAA Accident PackageItem 21 · .PDF · 23.4 MB3-O Air Traffic Control ASR Google Earth Plots of SWA1380Item 22 · KML · 217 KB3-P Air Traffic Control 84th RADES ARSR 4 Primary Target Radar Data with Height Finder ActiveItem 23 · KML · 35 KB3-Q Air Traffic Control Google Earth Plot SWA1380Item 24 · KML · 217 KB5 - Meteorology - Weather Factual ReportItem 25 · .PDF · 4.1 MB5 - Meteorology - Weather Attachment 1Item 26 · .GIF · 10.1 MB6-A Survival Factors Factual ReportItem 27 · .PDF · 2 photos · 341 KB6-B Survival Factors Factual Report - Attachment 1 - Flight Attendant and Passenger InterviewsItem 28 · .PDF · 92 KB6-C Survival Factors Factual Report - Attachment 2 - SWAU Training Staff InterviewsItem 29 · .PDF · 8.2 MB7-A Structures Factual ReportItem 30 · .PDF · 33 photos · 2.8 MB7-B Boeing Supporting DocumentationItem 31 · .PDF · 757 KB7-C UTAS Supporting DocumentationItem 32 · .PDF · 925 KB7-D FAA Supporting DocumentationItem 33 · .PDF · 789 KB7 - Structures Report 2 Tech Review VersionItem 34 · .PDF · 3.3 MB7 - Report from Party - CollinsItem 35 · .PDF · 7.7 MB7 - Report from Party - CFMItem 36 · .PDF · 4.0 MB7 - Slat EQA ReportItem 37 · .PDF · 9.8 MB7 - T12 eqaItem 38 · .PDF · 6.1 MB7 - Structures Attachment 1 Pressurization System DescriptionItem 39 · .PDF · 164 KB8 - A Powerplant Group Chairman's Factual ReportItem 40 · .PDF · 69 photos · 13.2 MB8 - B CFM Supporting DocumentationItem 41 · .PDF · 1.2 MB8 - Powerplants errataItem 42 · .PDF · 142 KB10 - Flight Data Recorder - FactualItem 43 · .PDF · 8.2 MB10 - Flight Data Recorder - Attachment 1Item 44 · .CSV · 57.8 MB11 - Maintenance RecordsItem 45 · .PDF · 12.0 MB12 - Cockpit Voice Recorder FactualItem 46 · .PDF · 1.1 MB15 - Materials Laboratory Factual Report 18-049Item 47 · .PDF · 7.5 MB17-C Timeline StudyItem 48 · .PDF · 18 photos · 3.5 MBTranscript - Public HearingItem 49 · .PDF · 392 KBParty Submission - BoeingItem 50 · .PDF · 879 KBParty Submission - CFMItem 51 · .PDF · 932 KBParty Submission - CollinsItem 52 · .PDF · 980 KBParty Submission - SWAItem 53 · .PDF · 334 KB

FAA reports on this event · 1

The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.