- Date
- July 31, 1989, 13:35 local (20:35 UTC)
- Place
- Rialto, CA
- Injuries
- 2 uninjured
- Damage
- Substantial damage
- Phase of flight
- Landing
- Aircraft
- N10857Bell 206B
- Weather
- Visual (VMC) · Day
- Status
- Completed · report March 29, 1991
- Report
- Approved by Office Director
- FAA report
- 19890731026159A
- Case key
- 26458
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
Failure to install two of the four required nuts which retain the high speed coupling input drive shaft to the transmission.
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
During a practice autorotation with a power recovery, the flight instructor heard a noise from the rear of the helicopter. When the power recovery was attempted, the engine responded to the throttle application but the low RPM warning horn activated and the helicopter struck the ground in a level attitude which caused the main rotor blades to sever the tailboom. Examination of the high speed output driveshaft coupling, transmission end, showed that the four bolts were installed but the four nuts and four washers could not be found in the assembly. Two nuts were found in the scupper drain of the transmission deck.
Aircraft
- Registration
- N10857
- Reported as
- Bell 206B
- Category
- Helicopter
- Serial number
- 2974
- Airframe hours
- 2,688
- Engine
- Allison 250-C20-B, 420 horsepower, turbo shaft
- Damage
- Substantial damage
- Flight
- Instructional · Part 91
- Operator
- Ca. Amer. Research Information
- Registered owner
- California American Research
- Airworthiness certificate
- Standard, Normal
- Last inspection
- Annual · July 20, 1989 · 20 hours before
- Airport
- L67 · Rialto Munic. Arpt
Flight crew
As NTSB recorded them. NTSB leaves out names.
- Role
- Pilot
- Age
- 41
- Certificates
- Commercial, Flight instructor
- Airplane ratings
- Single-engine land, Multi-engine land
- Instrument ratings
- Airplane
- Medical
- Class 2, Valid Medical--no waivers/lim.
- Seat
- Left
- Flight hours
- 5,600 total · 1,400 in this make and model · 80 in the last 90 days · 22 in the last 30 days · 2 in the last 24 hours
Weather
- Conditions
- Visual (VMC) · Day
- Wind
- 240° at 5 knots
- Visibility
- 5 statute miles
- Lowest ceiling
- None
- Temperature
- 81 °F
FAA reports on this event · 1
The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.