FlarePath

What happened

NTSB summary, verbatim

The diffuser case of a Pratt & Whitney PW2037(M) engine installed on a B757-200 airplane ruptured during takeoff roll at Hartsfield-Jackson Atlanta International Airport, Atlanta, Georgia (ATL). The force of the case rupture caused the hinge-mounted core cowl halves to distort and strike the leading edge and underside of the airplane's left wing, resulting in minor airplane damage. Metallurgical investigation and review of the engine's maintenance records determined that cracks in the engine's diffuser case rear flange (M-flange) and cracks in the HPT case forward flange (M-flange) were not detected when the cases underwent fluorescent penetrant inspection (FPI) during the engine's last shop visit, 3,479 cycles before the event. The undetected cracks continued to propagate, leading to the in-service diffuser case rupture. The reason for the ineffective inspection was not determined, but was narrowed to chronological- and operator-based scenarios. A suspect population of 50 engines was identified that included sub-populations for both possibilities. The FAA published airworthiness directive (AD) 2014-05-32, requiring the M-flanges of PW2037, PW2037D, PW2037M, PW2040, PW2040D, PW2043, PW2143, PW2240, PW2337, PW2643, and F117-PW-100 engines in the identified suspect population to undergo eddy current inspection within 100 flight cycles or 30 days. No additional cracks were found. As a result of the investigation, the FAA published airworthiness directive (AD) 2014-05-32, which requires the M-flanges of PW2000 engines with certain diffuser and HPT cases installed to undergo eddy current inspection within 100 flight cycles or 30 days. AD 2014-05-32 also requires that high-sensitivity FPI penetrant be used when accomplishing FPI of the PW2037, PW2037D, PW2037M, PW2040, PW2040D, PW2043, PW2143, PW2240, PW2337, PW2643, and F117-PW-100 diffuser case M-flange and the HPT case M-flange. In addition, AD 2014-05-32 makes the performance of diffuser and HPT case M-flange high-sensitivity FPI at every piece part opportunity an airworthiness limitation for PW2037, PW2037D, PW2037M, PW2040, PW2040D, PW2043, PW2146, PW2240, PW2337, PW2643, and F117-PW-100 engines.

Photographs

21the aircraft, and what the investigators found

The aircraft before the accident

Wreckage and site documentation · 20 photographs from the docket

Photographs are NTSB docket attachments — works of the US government, in the public domain. Captions are the Board’s own.

Probable cause

the Board's determination

the return to service of overhauled airplane engine parts with undetected fatigue cracks, resulting in complete loss of engine power and uncontained engine failure. A contributing factor was the inadequate diffuser and HPT case inspection procedure.

Occurrence sequence

2 stepsNTSB coding · CICTT taxonomy

1 · Takeoff-rejected takeoff
Uncontained engine failure
defining event
2 · Takeoff-rejected takeoff
Loss of engine power (partial)

Findings

2 causal · 2 contributing

CAUSE
Aircraft › Aircraft power plant › Engine (turbine/turboprop) › Combustion section — Incorrect service/maintenance
CAUSE
Aircraft › Aircraft power plant › Engine (turbine/turboprop) › Combustion section — Inadequate inspection
FACTOR
Aircraft › Aircraft power plant › Engine (turbine/turboprop) › Combustion section — Fatigue/wear/corrosion
FACTOR
Aircraft › Aircraft power plant › Engine (turbine/turboprop) › Combustion section — Failure

Sequence of events

5 timed eventsfrom the FDR factual report · claude-sonnet-5

15:15:45 EDT (approx.)Pre-event/FDR power onp.3
FDR first powered on and started recording data before the event
~15:19:XX EDT (during takeoff roll, about 9 seconds of acceleration)Takeoff roll - accelerationp.3
Aircraft accelerated for approximately 9 seconds, computed airspeed reached a maximum of 60 knots
~60 kiasTakeoff rollp.1
Flight crew heard a loud bang and noted left engine fire indications; No. 1 (left) engine failure during takeoff roll
Following the bang/fire indicationTakeoff roll - rejected takeoffp.3
Captain aborted the takeoff; aircraft decelerated for approximately 23 seconds
After rejected takeoffPost-event taxip.1
The airplane was taxied back to the gate without further incident and the passengers were deplaned normally

NTSB analysis

from the final report

The diffuser case of a Pratt & Whitney PW2037(M) engine installed on a B757-200 airplane ruptured during takeoff roll at Hartsfield-Jackson Atlanta International Airport, Atlanta, Georgia (ATL). The force of the case rupture caused the hinge-mounted core cowl halves to distort and strike the leading edge and underside of the airplane's left wing, resulting in minor airplane damage. Metallurgical investigation and review of the engine's maintenance records determined that cracks in the engine's diffuser case rear flange (M-flange) and cracks in the HPT case forward flange (M-flange) were not detected when the cases underwent fluorescent penetrant inspection (FPI) during the engine's last shop visit, 3,479 cycles before the event. The undetected cracks continued to propagate, leading to the in-service diffuser case rupture. The reason for the ineffective inspection was not determined, but was narrowed to chronological- and operator-based scenarios. A suspect population of 50 engines was identified that included sub-populations for both possibilities. The FAA published airworthiness directive (AD) 2014-05-32, requiring the M-flanges of PW2037, PW2037D, PW2037M, PW2040, PW2040D, PW2043, PW2143, PW2240, PW2337, PW2643, and F117-PW-100 engines in the identified suspect population to undergo eddy current inspection within 100 flight cycles or 30 days. No additional cracks were found. As a result of the investigation, the FAA published airworthiness directive (AD) 2014-05-32, which requires the M-flanges of PW2000 engines with certain diffuser and HPT cases installed to undergo eddy current inspection within 100 flight cycles or 30 days. AD 2014-05-32 also requires that high-sensitivity FPI penetrant be used when accomplishing FPI of the PW2037, PW2037D, PW2037M, PW2040, PW2040D, PW2043, PW2143, PW2240, PW2337, PW2643, and F117-PW-100 diffuser case M-flange and the HPT case M-flange. In addition, AD 2014-05-32 makes the performance of diffuser and HPT case M-flange high-sensitivity FPI at every piece part opportunity an airworthiness limitation for PW2037, PW2037D, PW2037M, PW2040, PW2040D, PW2043, PW2146, PW2240, PW2337, PW2643, and F117-PW-100 engines.

BOEING 757-251Delta Air Lines Inc