- Date
- March 21, 1992, 11:00 local (19:00 UTC)
- Place
- Huron, CA
- Injuries
- 1 uninjured
- Damage
- Destroyed
- Phase of flight
- Maneuvering
- Aircraft
- N93478Hiller UH-12E
- Weather
- Visual (VMC) · Day
- Status
- Completed · report August 26, 1993
- Report
- Approved by Office Director
- Safety recommendations
- Yes
- FAA report
- 19920321007009A
- Case key
- 27578
From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.
On this page
Probable cause
A separation of the control rotor cuff due to fatigue.
Sequence of events
NTSB’s coding before 2008: each occurrence and phase of flight, and the causes and factors under it. The codes are defined in NTSB’s coding manual.
Analysis
The pilot experienced a sudden violent main rotor vibration while on a spray run over an orchard. While maneuvering at about 12 feet above the tree tops, one of the control rotor blade assemblies separated from the rotor hub. An examination of the separated control rotor assembly revealed a fatigue crack that originated at the rotor cuff retaining bolt hole. The control rotor cuff is the subject of a 100-hour recurring inspection as a result of an airworthiness directive (AD). The AD was complied with during the last 100-hour inspection. The cuff had accumulated 88.8 hours of service since the last 100-hour inspection.
Aircraft
- Registration
- N93478
- Reported as
- Hiller UH-12E
- Category
- Helicopter
- Serial number
- 1608
- Airframe hours
- 5,440
- Engine
- Lycoming VO-540-C2A, 305 horsepower, reciprocating
- Damage
- Destroyed
- Flight
- Aerial application · Part 137
- Operator
- Huron Ag Helicopters Inc.
- Registered owner
- Huron Ag Helicopters Inc.
- Airworthiness certificate
- Special, Restricted (Special)
- Last inspection
- 100 hour · September 22, 1991 · 89 hours before
Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.
Flight crew
As NTSB recorded them. NTSB leaves out names.
- Role
- Pilot
- Age
- 46
- Certificate
- Commercial
- Airplane ratings
- Single-engine land
- Medical
- Class 2, Valid Medical--w/ waivers/lim
- Seat
- Center
- Flight hours
- 5,500 total · 4,000 in this make and model · 5,200 as pilot in command · 40 in the last 90 days · 40 in the last 30 days · 1 in the last 24 hours
Weather
- Conditions
- Visual (VMC) · Day
- Wind
- 180° at 3 knots
- Visibility
- 15 statute miles
- Lowest ceiling
- None
- Temperature
- 64 °F
FAA reports on this event · 1
The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.
Other investigations on N93478 · 1
Matched to the same aircraft by N-number and date.