British JETSTREAM 3201 N488UE

Summary

On 20 October 2000 at about 21:00 local time, a British JETSTREAM 3201 registered N488UE, operated by Atlantic Coast Airlines, was involved in an accident near Dulles, Virginia, United States. 12 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

20 October 2000 at 21:00

Classification

Accident

Location

Dulles, Virginia, United States

Coordinates

Not recorded

Aircraft

British JETSTREAM 3201

Registration

N488UE

Category

Airplane

Engines

2

Operator

Atlantic Coast Airlines

Operating rule

Part 121: Air Carrier

Purpose of flight

Unknown

Phase of flight

Not recorded

Route

Newport News → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Night/Dark

NTSB number

IAD01FA006

Nobody was injured.

The manufacturer's lack of dimensional inspection and repair requirements for the gearbox forward and aft diaphragm, which caused the bull gear to shift and resulted in an uncontained separation of the bull gear during flight

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

Read the full NTSB narrative

The airplane was on the arrival to the destination airport, and was cleared to descend from 8,000 feet to 5,000 feet. A descent was initiated by reducing power on both engines. As the airplane descended through 6,500 feet, the crew heard a loud bang, followed by a vibration, and illumination of the right engine 'FIRE' warning light. The right engine RPM dropped to 80 percent and stabilized at that value. The fire bell also sounded. The crew identified the right engine, discharged fire bottle, and the 'FIRE' warning light extinguished. The engine was secured and the airplane landed uneventfully at IAD. Examination of the airplane revealed that the right engine bullgear experienced an uncontained separation in flight. A 4 5/8-inch long section of the bullgear rim penetrated the right side of the fuselage and was recovered from the left side interior cabin wall above seat 1A's seat cushion. Examination of the right engine gearbox revealed that the bull gear was broken into at least six pieces. The gearbox diaphragm's bull gear bearing bore was measured and found to be over the engine manual's allowable wear limit. The engine's maintenance records show that the bull gear was installed new at the last repair, 597 hours and 776 cycles before the event. Metallurgical examination of the bull gear revealed an initial fatigue fracture that originated on the front face of the bull gear outboard of the hub. There were two other fatigue fractures that were on either side of the initial fatigue fracture. The examination also revealed that the bull gear's web thickness and material hardness conformed to the manufacturer's design requirements. As a result of this investigation, the FAA was considering an airworthiness directive that would require a recurring sampling of oil to be analyzed for increased levels of metal that could be indicative to bull and high speed pinion gear wear.

Quoted verbatim from the NTSB record.