Bell 206B N474SF

Summary

On 12 July 2001 at about 20:30 local time, a Bell 206B registered N474SF, operated by McClelland, John and Teri, was involved in an accident near San Francisco, California, United States. 4 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

12 July 2001 at 20:30

Classification

Accident

Location

San Francisco, California, United States

Nearest airport

San Francisco International (SFO)

Coordinates

37.6104, -122.3807

Aircraft

Bell 206B

Registration

N474SF

Category

Helicopter

Engines

1

Operator

McClelland, John and Teri

Operating rule

Part 91: General Aviation

Purpose of flight

Business

Phase of flight

Not recorded

Route

San Francisco → San Francisco

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

LAX01LA243

Nobody was injured.

The failure of the accessory gearbox 2 1/2 bearing in fatigue resulting in the complete loss of engine power and a subsequent forced landing. The pilot's failure to maintain directional control during the autorotational flare maneuver is also causal. The operator's failure to comply with the recommendations in the engine service manual regarding removal of the engine from service for detailed inspection is a factor.

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

Read the full NTSB narrative

The helicopter made a hard landing and severed the tail boom after an in-flight engine failure and autorotation. The pilot reported seeing an engine chip light and hearing a whining sound in the engine about 700 feet agl. An engine out light followed by a complete engine failure occurred about 1 minute later. The pilot had been descending to land in an open field by that time. The collective was lowered to enter an autorotation and aft cyclic applied to slow the forward airspeed. As he neared the bottom of the maneuver, he pulled collective pitch to cushion the landing; however, the helicopter abruptly spun 90 degrees to the left. The main rotor blades struck the tail boom and the ground. The tail boom was separated from the helicopter. After an inspection and teardown of the engine, the 2 1/2 bearing was found to have failed in fatigue. Records revealed that a chip light had been reported in the same helicopter on a flight (4) days prior. Before being returned to service, a magnetic plug inspection/cleaning and an engine ground test run were performed. According to the Allision 250 Series Operation and Maintenance Manual, when either a chip light is encountered after a gearbox flush and a second ground test run has been performed or when a total of (4) chip lights have been encountered within 50 hours of engine operation, the engine must be removed from service and sent to the manufacturer's authorized maintenance center.

Quoted verbatim from the NTSB record.