Boeing 767-223(ER) N330AA

Summary

On 2 June 2006 at about 19:27 local time, a Boeing 767-223(ER) registered N330AA, operated by American Airlines Inc, was involved in an incident near Los Angeles, California, United States. 3 people were on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

2 June 2006 at 19:27

Classification

Incident

Location

Los Angeles, California, United States

Nearest airport

Los Angeles (KLAX)

Coordinates

33.9708, -118.2396

Aircraft

Boeing 767-223(ER)

Registration

N330AA

Category

Airplane

Engines

2

Operator

American Airlines Inc

Operating rule

Unknown

Phase of flight

Not recorded

Aircraft damage

Substantial

NTSB number

ENG06IA018

Nobody was injured.

The HPT stage 1 disk failed from an intergranular fatigue crack because of GE's inadequate design of the CF6-80 series HPT stage 1 disk. The inadequate design of the disk resulted in a high stress area in the blade slot bottom aft corner that was at or nearly at the material's capability so that there was no damage tolerance such that a small dent could cause a crack to initiate and propagate to failure. Contributing to the disk's failure was the FAA's failure to mandate an accelerated inspection schedule after a previous CF6-80A uncontained HPT stage 1 disk failure had occurred and after other CF6-80A HPT disks had been found during routine overhaul to have cracks in the blade slot bottom aft corners.

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

Read the full NTSB narrative

The Boeing 767 was undergoing a high-power test of the left-hand General Electric (GE) CF6-80C2 engine to troubleshoot a pilot's report of the engine being unable to make climb thrust. During the test, the engine experienced an uncontained failure of the high pressure turbine (HPT) stage 1 disk. Examination of the pieces of the disk revealed the disk failed from an intergranular fatigue crack that originated from a small depression on the blade slot bottom aft corner radius. There were two other intergranular fatigue cracks that originated from small depressions on other blade slot bottom aft corner radii. Intergranular fatigue cracks are typically associated with very high stresses that exceed the material's capability. GE issued service bulletins (SB) to require inspections of CF6-80A and -80C2 HPT stage 1 disks that the FAA mandated with airworthiness directives (AD), but the SBs and AD did not establish a compliance schedule. When the SBs and AD was revised to establish a compliance schedule, the schedule was such that disks with much higher cycles since new, than those that had previously failed or were found cracked, were permitted to remain in service. On August 26, 2006, the Safety Board issued safety recommendation A-06-60 through A-06-64, which addressed these deficiencies. The recommendations can be found at the following url address: http://www.ntsb.gov/recs/letters/2006/A06_60_64.pdf.

Quoted verbatim from the NTSB record.