Bell 206L-1 N87WC

Summary

On 21 April 1998 at about 04:30 local time, a Bell 206L-1 registered N87WC, operated by Helinet, was involved in an accident near Los Angeles, California, United States. 2 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

21 April 1998 at 04:30

Classification

Accident

Location

Los Angeles, California, United States

Coordinates

34.0602, -118.2400

Aircraft

Bell 206L-1

Registration

N87WC

Category

Helicopter

Engines

1

Operator

Helinet

Operating rule

Part 135: Air Taxi & Commuter

Purpose of flight

Unknown

Phase of flight

Not recorded

Route

Ontario → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Night/Dark

NTSB number

LAX98LA140

Nobody was injured.

An overtemp of the engine during start within 10 hours of the accident, and the failure to report the event to the maintenance facility.

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

Read the full NTSB narrative

The helicopter lost engine power while on approach to a rooftop helipad, approximately 50 feet high and 50 feet short of the building. The pilot landed the helicopter on the roof, severing the tail boom at the horizontal stabilizer. The Safety Board conducted a teardown examination of the engine. Disassembly of the gas producer turbine support from the power turbine support revealed a fractured first stage turbine wheel, which displayed a nine airfoil chordal segment of the rim separated from the larger portion of the wheel. According to the Allison metallurgist, both the first and second stage turbine wheel blades exhibited evidence of operation of temperatures in excess of 2,200 degrees Fahrenheit. Both primary and secondary rim crack fractures exhibited evidence of exposure to extreme temperatures during the engine start sequence. No evidence of engine oil fire was observed on the gas producer turbine components. Chemical analysis of the affected gas producer turbine components indicated conformance to the specified material types. The Allison metallurgist reported that an overtemperature event occurred as a result of a hot start when both wheels were not at operating temperature; an overtemperature event occurring when the engine was at operating temperatures would have melted the first stage turbine wheel blades. The size of the gamma prime at the altered locations indicated the event occurred approximately within the last 10 hours of engine operation. No hot start or overtemperature event was reported to the maintenance facility.

Quoted verbatim from the NTSB record.