What aircraft was involved and where did it happen?

The accident on 2000-03-19 involved a Bell 212, registration N415B, at Snelling, CA.

Helicopter Impacted Terrain Following Mast Bumping and Loss of Control (N415B)

On March 19, 2000, a Bell 212 (registration N415B) was involved in an aviation accident near Snelling, CA. Investigators recorded the probable cause as: the in-flight separation of the main rotor mast while in cruise flight following a mast bumping event. The reason for the mast bumping event was not determined. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

A twin-engine helicopter struck terrain after a mast bumping event and loss of control. The pilot had a cast on his right leg and had recently returned to flying after a 3-month hiatus. The initiating event of the mast bumping remains unknown.

Accident Sequence

A twin-engine helicopter impacted terrain following a mast bumping event and subsequent loss of control. The helicopter was the second in a flight of two and trailed the lead helicopter by a short distance. The lead pilot noticed the second helicopter wreckage after the pilot did not receive a radio response from the accident pilot. The lead pilot reported receiving no distress transmissions from the accident pilot. The lead pilot stated they were in cruise flight between 400–500 feet AGL at 100 knots and encountered a large bird about 1 mile before the accident.

Wreckage Evidence

A 12-foot section of one of the main rotor blades was found early in the wreckage debris path, which was approximately 1,000 feet in length and oriented along the flight's course. Cut portions of the left skid, battery door, and left elevator were also found early in the debris path. The separated main rotor blade underwent an overhaul approximately 8.3 hours prior to the accident. The main rotor mast displayed evidence of a mast bumping event, with indentations corresponding to the blade stops. The mast separated at the blade stop area.

Pilot Background

The commercial helicopter pilot was wearing a cast on his right leg that extended from below his knees to his toes. The pilot received a checkout flight after not flying for 3 months. According to the pilot who provided the checkout flight, the accident pilot performed a few traffic pattern operations and was deemed able to fly. A mechanic who flew with the accident pilot during the first legs of the flight indicated the pilot was able to fly with no problems.

Investigation Findings

Though there was evidence of a mast bumping event, the initiating event is unknown. Examination of the wreckage disclosed no anomalies that would have prevented normal system operation. The engines displayed evidence of rotation at the time of ground impact. The main rotor blade with the separated section was examined, and its failure was a result of overload separation and did not delaminate in flight.

2000-03-19: Bell 212 (N415B) — Snelling, CA