Sikorsky S-58ET N15AH

Summary

On 12 July 2003 at about 17:28 local time, a Sikorsky S-58ET registered N15AH was involved in an accident near Rancho P.Verdes, California, United States. One person was on board and one was seriously injured. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

12 July 2003 at 17:28

Classification

Accident

Location

Rancho P.Verdes, California, United States

Coordinates

33.7544, -118.3300

Aircraft

Sikorsky S-58ET

Registration

N15AH

Category

Helicopter

Engines

2

Operator

Not recorded

Operating rule

Part 133: Rotorcraft Ext. Load

Purpose of flight

Other Work Use

Phase of flight

Not recorded

Route

Rancho P.Verdes → Rancho P.Verdes

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

LAX03FA232

1 person was seriously injured.

A total loss of antitorque control, due to the fatigue-induced failure of a gear within the drive shaft's intermediate gear box (IGB). Contributing factors were the pilot's improper on-ground decision to continue flight operations following discovery of material on the IGB's chip plug, and his failure to immediately jettison the external load.

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

Read the full NTSB narrative

The helicopter experienced a loss of tail rotor drive while maneuvering during a Federal Aviation Administration authorized low altitude external long line host operation, and collided with the ground in the subsequent descent. At the time, the operation was being performed in an area of the height-velocity curve that did not allow for a successful autorotative landing. Witnesses reported that minutes prior to the accident the pilot had made a precautionary landing due to illumination of the intermediate gearbox (IGB) chip light. The pilot removed, inspected, and cleaned the chip plug that contained metallic-like particles. During this action, the pilot was overheard to express concern to a ground crewmember by stating "this can be a problem." The pilot elected to continue flight operations. About 13 minutes later, within 200 feet above ground level while lifting an air conditioner (AC) unit from a school building, the pinion gear (part number S1635-64114-101) going into the drive side of the helicopter's intermediate gearbox (IGB) failed. This resulted in a total loss of antitorque control, and the helicopter yawed and spun in a clockwise direction while descending, and the helicopter impacted the unoccupied schoolyard. The pinion gear for the intermediate gearbox was examined. The laboratory reported that the initiating failure event had resulted from a fatigued gear tooth. The failure occurred about 175 hours prior to the part reaching its 2,000-hour life limit. The external long line was still connected to the cargo hook. Examination of the cockpit disclosed that the electrical cargo release switch was not armed. Post accident tests established that both the electrical release and manual backup cargo release mechanisms functioned.

Quoted verbatim from the NTSB record.