Airbus A330 223 N855NW

Summary

On 26 October 2016 at about 22:50 local time, a Airbus A330 223 registered N855NW, operated by Delta Air Lines Inc, was involved in an incident near Seattle, Washington, United States. 120 people were on board and nobody was injured. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

26 October 2016 at 22:50

Classification

Incident

Location

Seattle, Washington, United States

Nearest airport

Seattle-Tacoma Intl (SEA)

Coordinates

47.4472, -122.3142

Aircraft

Airbus A330 223

Registration

N855NW

Category

Airplane

Year built

2004

Engines

2

Operator

Delta Air Lines Inc

Operating rule

Part 121: Air Carrier

Phase of flight

Not recorded

Route

Seattle → Chep Lap Kok

Aircraft damage

Not recorded

Weather

Unk

Light

Day

NTSB number

ENG17IA003

Nobody was injured.

A No. 1 engine fire caused by a fuel manifold supply line high cycle fatigue crack which led to a fuel leak that subsequently ignited on hot engine case surfaces. The fatigue crack originated and progressed due to elevated fuel manifold assembly vibration levels. Engine vibration testing identified a combustor tone that excites a natural (resonant) frequency of the fuel manifolds at specific engine speeds on Pratt & Whitney PW4000-94 and -100 inch fan series engines that feature a TALON II combustor.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The No. 1 engine fire was caused by a fuel leak that originated from a high cycle fatigue crack on the fuel nozzle No. 1 fuel manifold supply line. Fuel nozzle No. 1 is located at the 12 o'clock position on the engine, so the fuel that leaked from the crack ran down the diffuser case and ignited on the engine case surface. The diffuser case reaches high enough temperatures during engine operation to auto-ignite Jet A fuel. The greatest concentration of soot/discoloration was observed from the 6 to 9 o'clock positions between the forward flange of the HPT case to the aft flange of the diffuser case, consistent with fuel collecting at the bottom of the engine and in the lower half of the thrust reverser cowls and creating a rich fuel to air mixture. Engine vibration testing was performed on multiple PW4000-94 and -100 inch series fan engines featuring a TALON II combustor. The testing identified a combustor tone that excites a natural (resonant) frequency in the fuel manifold assemblies. The amplitude of the combustor tone varied significantly between the four engines tested and the reason for this variation has not yet been determined. Pratt & Whitney released service bulletins for both the PW4000-94 inch and -100 inch fan engines recommending the installation of brackets and clamps on the fuel manifold assemblies. Engine vibration testing was performed on the same engine before and after installation of the brackets and clamps and the testing confirmed that the design was effective in dampening the elevated vibration levels driven by the combustor tone.

Quoted verbatim from the NTSB record.