Pilot Debrief

ROBINSON HELICOPTER R22 BETA II near Phoenix, AZ — 2014-12-30

Final reportWPR15IA080
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Date
2014-12-30
Location
Phoenix, AZ, USA
Airport
IWA
Aircraft
ROBINSON HELICOPTER R22 BETA II
Registration
N7041X
Category
Helicopter
Highest injury
None
Fatalities
0
Phase of flight
Climb

Probable cause

The failure of the fanshaft due to fatigue.

NTSB narrative

The private pilot reported that he was practicing for the commercial pilot helicopter examination and was operating in the airport traffic pattern. The pilot stated that, while entering downwind, he climbed the helicopter to 1,900 ft and was accelerating it to 75 knots when he felt an "abnormal vibration" and smelled "something…burning." The low rotor rpm light illuminated, and the low rotor rpm horn sounded. He subsequently entered an autorotation, made an emergency call, and landed successfully off the runway on dirt. Postaccident examination of the helicopter revealed that the fanshaft had fractured circumferentially; the helicopter had a total time of 337 hours. Examination of the fanshaft revealed a crack in the fanwheel's base, which had beach marks that ran from the fanshaft's bearing surface out and down to the mounting surface, consistent with fatigue. The roller bearings and the races bearing surfaces had minor surface damage. The bearings and races were cut away from the fan shaft, which revealed a v-shaped fracture surface that had two cracks emanating from it. This area had sustained damage from the two halves contacting each other with every rotation of the crankshaft, and some material was missing. The fracture origin could not be determined due to the damage. The only anomaly identified during the examination was that the fanwheel was out of balance; however, this likely resulted from the fanshaft failure.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have aborted the flight after feeling abnormal vibration.

NTSB coding

  • Sys/Comp malf/fail (non-power) · Approach-VFR pattern downwind

Evidence available

  • 5 docket documents
View NTSB final reportView NTSB docket

Docket documents5

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