McDonnell Douglas 520N N112HD

Summary

On 20 May 1998 at about 15:00 local time, a McDonnell Douglas 520N registered N112HD was involved in an accident near Lanai City, Maui, Hawaii, United States. 5 people were on board and one had minor injuries. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

20 May 1998 at 15:00

Classification

Accident

Location

Lanai City, Maui, Hawaii, United States

Coordinates

20.8303, -156.9199

Aircraft

McDonnell Douglas 520N

Registration

N112HD

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 135: Air Taxi & Commuter

Purpose of flight

Unknown

Phase of flight

Not recorded

Route

Maui → Lanai City

Aircraft damage

Destroyed

Weather

VMC

Light

Night/Dark

NTSB number

LAX98LA166

1 person had minor injuries.

An oil starvation failure of the number 5 bearing for undetermined reasons.

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

Read the full NTSB narrative

The engine chip light illuminated during cruise and about 10 seconds later the engine out light flickered and then fully illuminated. As the pilot was performing an autorotation he and his passengers heard a loud bang, the helicopter landed on uneven terrain, and subsequently rolled over onto its side. A postcrash fire consumed the helicopter. The third turbine wheel was not located. The fourth turbine wheel was found remote from the helicopter with missing airfoils. In the 5 months prior to the accident, the power turbine had been removed for inspection and repaired several times due to one instance of an N2 lockup and chipped drive splines, and several instances of engine chip light illuminations with high temperatures and turbine rub. In each case, the plugs were removed, inspected per the manufacturer's maintenance manuals, and the oil system flushed. The day before the accident the engine chip light illuminated and the operator found a pasty substance on the chip detector. The chip detector was inspected in accordance with the manufacturer's maintenance manuals and the helicopter was then returned to service. Postaccident disassembly of the engine revealed an oil starvation failure of the No. 5 bearing and a subsequent failure of the No. 3 bearing due to a transfer of the axial loads normally carried by the No. 5 bearing. After the loss of the No. 5 bearing, there was an uncontained overspeed failure of the power turbine rotor to loss of power turbine gear train tooth engagement. Metal debris was encased on the tip of one of the chip detectors. The oil delivery tube that supplies oil to the No. 5 bearing was not recovered and was assumed to have been consumed in the postimpact fire.

Quoted verbatim from the NTSB record.