British BAE 146-200A N608AW

Summary

On 12 February 1999 at about 01:50 local time, a British BAE 146-200A registered N608AW was involved in an incident near Aspen, Colorado, United States. 88 people were on board and nobody was injured. The aircraft was slightly damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

12 February 1999 at 01:50

Classification

Incident

Location

Aspen, Colorado, United States

Coordinates

39.1900, -106.8198

Aircraft

British BAE 146-200A

Registration

N608AW

Category

Airplane

Engines

4

Operator

Not recorded

Operating rule

Part 121: Air Carrier

Purpose of flight

Unknown

Phase of flight

Not recorded

Route

Unknown → Denver

Aircraft damage

Minor

Weather

VMC

Light

Dusk

NTSB number

DEN99IA038

Nobody was injured.

The inadequate maintenance overhaul of the number four turbine disc by the manufacturer. A factor was the turbine blade's failure due to high cycle fatigue fracture.

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

Read the full NTSB narrative

The airplane experienced an uncontained number 4 engine failure during climb to cruise altitude. Examination of the engine revealed that the number 4 turbine disc had all its blades separated just above the blade platform except 1, which separated just below the blade platform. According to maintenance records, the number 4 turbine disc assembly was installed 22.5 hours or 22 cycles prior to this event. The manufacturer of the turbine disc said that the wheel was new; however, all 60 of the blades had seen previous use. A high-cycle fatigue crack was found in the one blade which had separated below the blade platform. The metallurgist noted that the fatigue crack originated from a fretting damage mark located at the fir-tree portion. The manufacturer reported that 9 blade retention pins, which were used to prevent blade radial movement, did not meet the requirement of no more than 0.005 inch clearance between pen head and wheel. They further reported that blade stress concentration was induced by the wheel broach slots sharp edges.

Quoted verbatim from the NTSB record.