Robinson R22 BETA N7779M

Summary

On 27 June 2011 at about 17:23 local time, a Robinson R22 BETA registered N7779M, operated by Don S. Arsenault, was involved in an accident near Del Valle, Texas, United States. One person was on board and one died. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

27 June 2011 at 17:23

Classification

Accident

Location

Del Valle, Texas, United States

Coordinates

30.1597, -97.5997

Aircraft

Robinson R22 BETA

Registration

N7779M

Category

Helicopter

Engines

1

Operator

Don S. Arsenault

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Taylor → Luling

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN11FA422

1 person died.

The divergence of the main rotor from its normal plane of rotation for reasons that cannot be determined because the pilot’s control inputs leading up to the event are unknown, resulting in mast bumping and main rotor blade separation.

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

Read the full NTSB narrative

The helicopter was flying across a river when witnesses heard a loud "pop" or "bang" and saw something fall from the helicopter into the river. They heard the helicopter crash, saw smoke, and ran to the crash site. One main rotor blade was found approximately 780 feet from the wreckage. The other main rotor blade was found approximately 975 feet from the wreckage in the opposite direction. Both blades had separated from the main rotor hub at their coning hinges. All components of the helicopter were accounted for with the exception of portions of both coning bolts. The investigation was unable to locate the object observed falling from the helicopter or determine what it was. Examination of the rotor head components, including the recovered portions of the coning bolts, revealed fracture features consistent with overload failure and mechanical damage indicative of mast bumping (contact between the main rotor blades and the mast). The main rotor blade pitch links and attaching hardware displayed compression buckling and bending overload features consistent with an out-of-control main rotor that had diverged from its normal plane of rotation. The helicopter manufacturer reported that the damage signatures were consistent with both low-G mast bumping and low rotor rpm rotor stall. Low-G mast bumping is a phenomenon specific to two-bladed teetering rotor systems in which the rotor disc becomes unloaded, typically due to a cyclic pushover. Low rotor rpm rotor stall is a different phenomenon in which the main rotor blades experience an aerodynamic stall due to low rotor rpm caused either by the pilot raising the collective too much or by a loss of engine power followed by the pilot lowering the collective too slowly. Rotor blade stall can lead to mast bumping. The pilot’s control inputs leading up to the event are unknown, and, therefore, the reason for the main rotor divergence could not be determined.

Quoted verbatim from the NTSB record.