Accident Boeing 737-7H4 (WL) N766SW, Saturday 27 August 2016
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Date:Saturday 27 August 2016
Time:09:22
Type:Silhouette image of generic B737 model; specific model in this crash may look slightly different    
Boeing 737-7H4 (WL)
Owner/operator:Southwest Airlines
Registration: N766SW
MSN: 29806/537
Year of manufacture:2000
Total airframe hrs:58344 hours
Engine model:CFMI CFM56-7B24
Fatalities:Fatalities: 0 / Occupants: 104
Other fatalities:0
Aircraft damage: Substantial, repaired
Category:Accident
Location:26 km S of Biloxi, MS -   United States of America
Phase: En route
Nature:Passenger - Scheduled
Departure airport:New Orleans International Airport, LA (MSY/KMSY)
Destination airport:Orlando International Airport, FL (MCO/KMCO)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
A Southwest Airlines Boeing 737-7H4 (WL) operating flight WN3472 suffered an in-flight loss of an engine air inlet cowl near Biloxi, Mississippi. A safe diversion was carried out.
The airplane departed New Orleans International Airport, Louisiana at 09:10 hours local time for a flight to Orlando International Airport, Florida. While climbing through FL310, about 26 km south off Biloxi, the air inlet cowl of the nr.1 engine broke away. The flight contacted Houston Center about 09:22, stating: "engine failure...we've lost number one engine, we're descending". Initially the flight was cleared down to FL260. The flight then radioed "472 we need get down below ten". The flight was then cleared down to FL240 and the flight again stated that they needed to get down to 10000 feet.
While descending the crew made two unintentional transmissions to Houston Center in which they can be heard working the related emergency checklist with a sound indicating the possible use of oxygen masks by the crew.
The flight then diverted to Pensacola were it landed about 09:40. After landing damage was observed to the left hand wing root, a 5-inch by 16-inch hole in the fuselage and dents in the left hand horizontal stabilizer leading edge.

The NTSB on September 12 reported the following initial findings from the engine examination include:
- One fan blade separated from the fan disk during the accident flight and
- The root of the separated fan blade remained in the fan hub; however, the remainder of the blade was not recovered.
- The fracture surface of the missing blade showed curving crack arrest lines consistent with fatigue crack growth. The fatigue crack region was 1.14-inches long and 0.217-inch deep,
- The center of the fatigue origin area was about 2.1 inches aft of the forward face of the blade root. No surface or material anomalies were noted during an examination of the fatigue crack origin using scanning electron microscopy and energy-dispersive x-ray spectroscopy.

Probable Cause: A low-cycle fatigue crack in the dovetail of fan blade No. 23, which resulted in the fan blade separating in flight and impacting the fan case. This impact caused the fan blade to fracture into fragments that traveled farther than expected into the inlet, which compromised the structural integrity of the inlet and led to the in-flight separation of inlet components. A portion of the inlet struck the fuselage and created a hole, causing the cabin to depressurize.

Accident investigation:
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Investigating agency: NTSB
Report number: DCA16FA217
Status: Investigation completed
Duration: 3 years and 7 months
Download report: Final report

Sources:

Flightradar24
WDSU
Southwest Airlines

Location

Images:


photo (c) NTSB; Jacksonville International Airport, FL (JAX/KJAX); August 2016; (publicdomain)


photo (c) NTSB; Jacksonville International Airport, FL (JAX/KJAX); August 2016; (publicdomain)


photo (c) NTSB; Jacksonville International Airport, FL (JAX/KJAX); August 2016; (publicdomain)


photo (c) Leslie Snelleman; Las Vegas-McCarran International Airport, NV (LAS/KLAS); 14 March 2012

Revision history:

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