BOEING 737 7H4SOUTHWEST AIRLINES CO
Philadelphia, PA, USA · 2018-04-17·N772SW
What happened
NTSB summary, verbatimThe 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.
Probable cause
the Board's determinationA 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.
Occurrence sequence
1 stepsNTSB coding · CICTT taxonomy- 1 · Enroute-climb to cruisePowerplant sys/comp malf/faildefining event
Findings
3 causal · 2 contributing- CAUSEAircraft › Aircraft power plant › Engine (turbine/turboprop) › Compressor section — Fatigue/wear/corrosion
- CAUSEAircraft › Aircraft structures › Nacelles/pylons structure › Nacelle/pylon misc structure — Damaged/degraded
- CAUSEAircraft › Aircraft structures › Windows-windshield system › Passenger compartment windows — Damaged/degraded
- FACTOROrganizational issues › Management › Resources › Availability of documents/info — FAA/Regulator
- FACTORPersonnel issues › Action/decision › Action › Lack of action — Cabin crew
Safety recommendations
7 issuedwhat changed because of this accidentTO THE FEDERAL AVIATION ADMINISTRATION: Require Boeing to determine the critical fan blade impact location(s) on the CFM56-7B engine fan case and redesign the fan cowl structure on all Boeing 737 next-generation-series airplanes to ensure the structural integrity of the fan cowl after a fan-blade-out event.
TO THE FEDERAL AVIATION ADMINISTRATION: Once the actions requested in Safety Recommendation A-19-17 are completed, require Boeing to install the redesigned fan cowl structure on new-production 737 next-generation-series airplanes.
TO THE FEDERAL AVIATION ADMINISTRATION: Once the actions requested in Safety Recommendation A-19-17 are completed, require operators of Boeing 737 next-generation-series airplanes to retrofit their airplanes with the redesigned fan cowl structure.
TO THE FEDERAL AVIATION ADMINISTRATION: Expand the Title 14 Code of Federal Regulations Part 25 and 33 certification requirements to mandate that airplane and engine manufacturers work collaboratively to (1) analyze all critical fan blade impact locations for all engine operating conditions, the resulting fan blade fragmentation, and the effects of the fan-blade-out-generated loads on the nacelle structure and (2) develop a method to ensure that the analysis findings are fully accounted for in the design of the nacelle structure and its components.
TO THE FEDERAL AVIATION ADMINISTRATION: Develop and issue guidance on ways that air carriers can mitigate hazards to passengers affected by an in-flight loss of seating capacity.
TO SOUTHWEST AIRLINES: Include the lessons learned from the accident involving Southwest Airlines flight 1380 in initial and recurrent flight attendant training, emphasizing the importance of being secured in a jumpseat during emergency landings.
TO THE EUROPEAN AVIATION SAFETY AGENCY: Expand your certification requirements for transport-category airplanes and aircraft engines to mandate that airplane and engine manufacturers work collaboratively to (1) analyze all critical fan blade impact locations for all engine operating conditions, the resulting fan blade fragmentation, and the effects of the fan-blade-out-generated loads on the nacelle structure and (2) develop a method to ensure that the analysis findings are fully accounted for in the design of the nacelle structure and its components.
Sequence of events
16 timed eventsfrom the FDR factual report · claude-sonnet-5- 10:31 (approx)Pre-taxip.4Engines started, number two (right) engine first and number one (left) engine second
- 10:42:34Takeoffp.4Engines began accelerating to takeoff power
- 10:43:11Takeoff rollp.4Pitch began to increase at computed airspeed of 123 kts
- 10:43:20Takeoff/liftoffp.4Gear weight on wheels signal transitioned from ground to air at computed airspeed of 157 kts
- ~10:50Climbp.5Aircraft climbed steadily for about seven minutes to a pressure altitude of about 17,250 ft
- ~10:57Climbp.5After three minutes at 22,000 ft, aircraft began to climb again
- 11:03:33.2Cruise/climbp.5Approximate time of fan blade off event; pressure altitude about 32,648 ft; engine 1 fan and core speeds decreased immediately and engine 1 vibration levels were elevated
- 11:03:33.3Post fan blade offp.5Discontinuity occurred in the data with missing data of at least 0.09 seconds, likely due to a momentary power interruption to the recording system
- 11:03:35Post fan blade offp.5Engine 1 control recorded a flameout protection recovery mode active
- 11 seconds after discontinuity (~11:03:44.3)Upsetp.5Aircraft reached peak recorded value of 41.3 degrees left roll before coming back to level attitude; roll was uncommanded, pilot inputs and force to the right
- 11:03:39Depressurizationp.5Cabin Altitude Warning recorded, signifying cabin altitude exceeded 10,000 ft
- 11:03:43Emergency descentp.5Aircraft began a rapid descent with descent rates in excess of 5,000 feet per minute
- 11:03:48Post fan blade offp.5Engine 1 Fault Dispatch Level A fault was recorded, correlated to a T12 (fan bypass duct temperature) fault
- 11:04:09Post fan blade offp.4Engine 1 fuel switch position transitioned from Run to Cutoff, ending flameout protection recovery mode
- 11:12:24Descentp.5Cabin Altitude Warning ceased when aircraft pressure altitude was about 9,150 ft
- 11:20:30Landingp.5Aircraft touched down with flaps set at 5 degrees at approximately 171 kts; reverse thrust used on right engine
NTSB analysis
from the final reportThe 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.