Pilot Debrief

Sikorsky S58 near Azusa, CA — 2019-09-11

Final reportWPR19LA255
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Date
2019-09-11
Location
Azusa, CA, USA
Aircraft
Sikorsky S58
Registration
N1168U
Category
Helicopter
Highest injury
None
Fatalities
0
Phase of flight
Cruise

Probable cause

The in-flight separation of a section of the tail rotor blade due to a fatigue crack, which resulted in the pilot’s forced autorotation into a field.

NTSB narrative

The pilot was conducting a ferry flight. During cruise flight while at an altitude of about 1,000 ft above ground level and at an airspeed of about 110 knots, one of the helicopter’s tail rotor blades separated, which resulted in a partial separation of the remaining tail rotor assembly and a forced autorotation. The remaining tail rotor assembly subsequently impacted the vertical stabilizer. The mechanic who performed the daily inspection of the helicopter before the accident flight did not observe any evidence of a crack on the tail rotor blades. The separated section of the tail rotor blade was not recovered. Postaccident fractographic examination of the tail rotor blade piece containing the root end revealed that most of the blade had cracked due to fatigue. No nicks, gouges, damage, or contamination were observed. Further examination revealed that the blade met the design specifications of the engineer drawings. Maintenance records revealed that the rotor blade was most recently repaired in April 2007, but details of the repair work were not available.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Maintenance records did not retain information on the last repair of the tail rotor blade.

NTSB coding

Evidence available

  • Photos
  • 7 docket documents
View NTSB final reportView NTSB docket

Docket documents7

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