Delta B752 at Las Vegas on Sep 6th 2017, engine fire

Last Update: October 1, 2019 / 21:04:31 GMT/Zulu time

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Incident Facts

Date of incident
Sep 6, 2017

Classification
Incident

Flight number
DL-1057

Aircraft Registration
N686DA

Aircraft Type
Boeing 757-200

ICAO Type Designator
B752

A Delta Airlines Boeing 757-200, registration N686DA performing flight DL-1057 (sched. dep Sep 5th) from Las Vegas,NV to New York JFK,NY (USA) with 184 people on board, was climbing out of Las Vegas' runway 26R and was about to be handed off to departure, when the crew declared emergency, declined the hand off stating they wanted to remain with tower and advised they needed to return to Las Vegas now. Tower cleared the flight for a left downwind runway 26L, the crew advised they did have a left engine (PW2037) fire and the engine was shut down. The aircraft landed safely on runway 26L about 12 minutes after departure. Attending emergency services reported seeing some smoke from the engine, a few minutes later the fire chief advised the fire was out. The crew subsequently advised the fire indication was out, too, and requested to taxi to the apron. The crew advised they had no fire bottle available anymore and requested fire engines to follow the aircraft and cover the right hand engine, the aircraft taxied to the apron with all fire engines following the aircraft.

A replacement Boeing 757-200 registration N535US reached New York with a delay of 7:45 hours.

On Oct 4th 2017 the NTSB reported that the left hand engine sustained an undercowl fire during takeoff from Las Vegas. The crew received an associated fire indication and warnings during rotation/initial climb, worked the related checklists, shut the engine down and discharged one fire bottle. The aircraft joined a downwind to return to Las Vegas, however, during the downwind a second left engine fire indication occurred, the crew discharged the second fire bottle. The aircraft landed overweight at McCarran Airport, emergency services sprayed fire retardent into the engine and cleared the aircraft to taxi to the apron under own power. The occurrence was rated an incident and is being investigated.

On Sep 19th 2019 the NTSB described tests and research as well as corrective actions:

Engine Examination and Disassembly

The No. 1 engine was removed from the airplane by Delta Air Lines (DAL) maintenance personnel at LAS and shipped to Delta TechOps- Atlanta, Georgia for examination and disassembly. Party members from DAL, Pratt & Whitney (P&W), Boeing, the Air Line Pilots Association (ALPA), the Federal Aviation Administration, and the National Transportation Safety Board met at Delta TechOps from September 26-28, 2017.

The compressor fan blades were all present and complete. Three fan blades located at the 6 o'clock position exhibited midspan shroud shingling and the fan blade tips were dug into the fan case rub strip and displaced about one inch in the aft direction. The fan could not be rotated by hand until the three shingled fan blades were forced back into their normal position with a pry bar. After the fan blades were adjusted, the fan could be spun smoothly by hand with concurrent rotation of the low pressure turbine. All exterior engine surfaces aft of the fan exit case were sooted. The engine had thermal damage and dark discoloration most concentrated over the high pressure compressor (HPC) and diffuser cases on the lower half of the engine (3 to 9 o'clock positions). Fuel components including the stator vane actuator (SVA), fuel flow transmitter (FFT), and associated fuel lines were thermally damaged with melted and missing material. The thermal damage to these components resulted in fuel system leak points. A SVA hose and tube assembly was found separated and hanging freely from the engine. A leak check of the fuel manifolds and fuel nozzle assemblies was performed by porting shop air into the fuel flow divider valve in accordance with engine maintenance manual procedures. When pressurized air was applied, an air leak was detected at fuel nozzle #7, located at the 3 o'clock position. The nozzle was removed from the engine as an assembly by cutting the fuel manifold supply line, so the fuel nozzle b-nut remained torqued. Preliminary x-rays of the nozzle were taken at Delta TechOps. The x-rays indicated the fuel nozzle b-nut was not properly installed. The fuel nozzle assembly SVA hose and tube assembly that was found separated were packaged and shipped to the P&W Materials and Processes Engineering Lab in East Hartford, Connecticut for additional analysis.

Materials Analysis

Fuel nozzle #7 was x-rayed at the P&W Quality and Standard Laboratory in East Hartford, Connecticut. The x-ray images confirmed that the b-nut was tilted relative to the nozzle platform and the end of the b-nut was not centered with the nozzle fuel supply tube (cross threaded). There was one or fewer threads engaged between the nozzle and b-nut.

The fuel nozzle assembly was sectioned. The o-ring on the fuel nozzle side was present and intact. The second o-ring located on the fuel manifold supply line side was damaged and o-ring fragments were recovered outside of the o-ring gland, near the conical washer seal.

The SVA hose and tube assembly was examined to verify there were no anomalies in the SVA flexible hose to rigid tube connection joint. The SVA flexible hose section exhibited thermal damage including a missing fire sleeve and hose liner. The hose liner was separated at one end of the connection to the rigid tube, but other joint connection remained intact. Metallographic sections were taken of both the intact joint and the separated joint and there were no significant differences observed.

Corrective Action

Following the event, DAL voluntarily inspected all PW2000 engines in the Delta TechOps repair shop, test cell, and spares pool for proper fuel nozzle installation, with no additional installation error findings. They also reviewed shop records and identified two in service engines that were overhauled/repaired at approximately the same time as the incident engine. The fuel nozzles on these engines were inspected with no findings. In an effort to avoid future installation errors, the diffuser and combustor assembly work instruction card was updated to add an inspector sign off requirement during the pneumatic leak check step of the fuel system assembly.

On Oct 1st 2019 the NTSB released their final report concluding the probable cause of the incident was:

A No. 1 (left) engine undercowl fire caused by a fuel nozzle installation error during engine overhaul at Delta TechOps. A fuel nozzle b-nut was cross threaded, which allowed fuel to leak on hot engine case surfaces and subsequently ignite.
Incident Facts

Date of incident
Sep 6, 2017

Classification
Incident

Flight number
DL-1057

Aircraft Registration
N686DA

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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