Delta B752 at Atlanta on Sep 5th 2018, uncontained engine failure
Last Update: April 7, 2022 / 15:44:16 GMT/Zulu time
Incident Facts
Date of incident
Sep 5, 2018
Classification
Incident
Airline
Delta Airlines
Flight number
DL-1418
Departure
Atlanta, United States
Destination
Orlando, United States
Aircraft Registration
N668DN
Aircraft Type
Boeing 757-200
ICAO Type Designator
B752
The NTSB reported they are investigating a reported uncontained engine failure on flight DL-1418. The crew shut the engine down and the aircraft returned to Atlanta for a safe landing. There were no injuries.
On Sep 21st 2018 the NTSB added, that the aircraft was climbing through about 18000 feet out of Atlanta when the crew heard a loud bang and received right hand engine failure indications. The right engine was shut down and the aircraft returned to Atlanta. A postflight inspection revealed minor damage to the airframe, an engine inspection revealed holes in the right nacelle inboard core cowl and in the engine high pressure turbine case.
On Mar 27th 2021 the NTSB released a brief preliminary report stating: "On September 05, 2018, about 2332 EDT, a Boeing 757 airplane, N668DN, experienced a right engine failure during climb at ~18,000 feet after departing Hartsfield-Jackson International Airport, Atlanta, Georgia. The flight crew reported hearing a loud bang and noting right engine failure indications. The right engine was shut down and the flight returned to ATL. The airplane damage was minor, and no injuries were reported. The airplane was being operated as a 14 CFR Part 121 scheduled flight from ATL to Orlando International Airport (MCO). The post-incident airplane inspection found holes in the right nacelle inboard core cowl and in the engine high pressure turbine case. "
On Apr 6th 2022 the NTSB opened their investigation docket. The power plant investigation reported:
a rotating seal located between the HPT stage 1 (S1) disk and S2 hub (the lenticular seal) had failed and unwrapped from its inner brace, destroying the turbine, and resulting in debris radially exiting the turbine cases. A segment of the seal displaced forward through the S1 blade path, penetrating the S1 turbine nozzle assembly and combustor, and damaging a fuel nozzle stem.
Metallurgical examination of the lenticular seal fragments identified a primary fracture surface, but the origin area was obliterated by secondary damage. However, the failure shared attributes with prior PW2000 lenticular seal failure events. Root cause investigations of those events led to the release of an improved-design lenticular seal. As a result of this investigation further corrective actions were taken to accelerate the update the PW2000 fleet with the improved-design seal.
...
There was no obvious fan blade damage. The LPT S7 turbine blades were intact. Metal debris was collected from inside the tailpipe.
The engine had accumulated 88,547 hours in 38,161 cycles since new and 14,505 hours in 6,460 cycles since last overhaul.
The airframe received additional minor damage:
There was a cluster of small scrapes and a 6-inch-long horizontal scuff at the aft end of the trunnion fairing. Local scratches and gouges were found on the underside of the right wing inboard and outboard of the trunnion fairing. There were three small sites of impact damage, including a through-puncture, on the right wing-to-body fairing. The right main landing gear (R MLG) door outer surface displayed two small nicks/scratches. Light impact damage was also observed along the right horizontal stabilizer leading edge. All the damage was consistent with external impact.
On Apr 7th 2022 the NTSB released their final report concluding the probable cause of the incident was:
A right engine turbine uncontainment resulting from failure of the high pressure turbine (HPT) lenticular seal due to a fatigue crack originating from an overheated region at a knife edge tip.
Contributing to the failure was Pratt & Whitney’s decision to introduce the temperature-resistant knifeedge coating as a new-part number lenticular seal on an attrition basis without the option to recoat existing lenticular seals, which delayed implementation of the more durable seal material into the fleet.
The NTSB added in their analysis:
Review of the engine service records found that the failed lenticular seal was installed new during a 2008 overhaul when the engine had accumulated 61,385 time since new (TSN) and 25,462 cycles since new (CSN). The seal was visually inspected and reinstalled during a 2013 overhaul at 74,042 TSN and 31,701 CSN. During the 2013 shop visit, 40% of the lenticular seal land honeycomb surface was replaced. The lenticular seal chromium carbide knife edge coating was not renewed, so that the secondrun lenticular seal knife edges with chromium carbide coating ran against new honeycomb material. The lenticular seal failed 6,460 cycles after the 2013 shop visit.
An improved-design lenticular seal with the chromium carbide knife edge coating replaced with a more durable, temperature-resistant aluminum oxide coating was released by PW2000 SB 72-754 in 2011. The new-design seal was introduced as a part replacement on an attrition basis (use down-change part until exhausted).
Aircraft Registration Data
Incident Facts
Date of incident
Sep 5, 2018
Classification
Incident
Airline
Delta Airlines
Flight number
DL-1418
Departure
Atlanta, United States
Destination
Orlando, United States
Aircraft Registration
N668DN
Aircraft Type
Boeing 757-200
ICAO Type Designator
B752
This article is published under license from Avherald.com. © of text by Avherald.com.
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