Boeing 757 N666DN

Summary

On 6 August 2008 at about 22:40 local time, a Boeing 757 registered N666DN, operated by Delta Air Lines Inc, was involved in an incident near Las Vegas, Nevada, United States. 170 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

6 August 2008 at 22:40

Classification

Incident

Location

Las Vegas, Nevada, United States

Nearest airport

McCarran International Airport (KLAS)

Coordinates

36.0800, -115.1522

Aircraft

Boeing 757

Registration

N666DN

Category

Airplane

Engines

2

Operator

Delta Air Lines Inc

Operating rule

Part 121: Air Carrier

Phase of flight

Not recorded

Route

Las Vegas → Jamaica

Aircraft damage

Not recorded

Weather

VMC

Light

Day

NTSB number

ENG08IA038

Nobody was injured.

The engine experienced an uncontained release of high pressure turbine material due to fatigue cracks that occurred on four consecutive blade retainig lugs on the 2nd stage turbine hub. The cracked lugs resulted in the release of four 2nd stage turbine blades that penetrated the engine's cases and nacelle. The lugs cracked due to loss of material and resultant increase in stress load on the blade slot serrations due to excessve grit blasting when the hub was being overhauled by Delta Air Lines. Contributing to the uncontained incident was the FAA's and Pratt & Whitney's failure to act in a timely manner when another PW2037 2nd stage turbine hub was found to have multiple cracks in the blade retaining lugs.

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

Read the full NTSB narrative

The Delta Air Lines Boeing 757 airplane had just started its takeoff roll from the McCarran International Airport, Las Vegas, Nevada, when the right engine, a Pratt & Whitney (P&W) PW2037, experienced an uncontained release of high pressure turbine material. The examination of the engine revealed a hole in the high pressure and low pressure turbine case flanges at the bottom of the engine in line with the 2nd stage turbine rotor. The engine was removed from the airplane and shipped to Delta's Technical Operations Center for disassembly. The disassembly revealed four adjacent 2nd stage turbine blades were missing. In addition, the 2nd stage turbine hub had four blade retaining lugs that were fractured. Metallurgical examination of the fractures determined the fractures were due to fatigue at elevated temperatures from multiple origins along the blade slot serrations. The metallurgical examination also revealed that there were no material defects in the hub. A dimensional inspection of the hub's blades slots showed that they were missing material. Delta reported that they had to use a grit blasting procedure that was more agressive to remove the varnish-like scale from the hub in order to clean it sufficiently to permit the fluorescent penetrant inspection. Although the incident hub was only grit blasted one time, maintenance records for another PW2037 2nd stage hub that was found to have multiple cracks in the blade slots showed that it had been grit blasted multiple times to clean the hub. Grit blasting tests conducted by P&W showed that if the appropriate grit blasting procedures were not adhered to that significant material loss could result.

Quoted verbatim from the NTSB record.