- Date
- April 21, 1990, 13:10 local (21:10 UTC)
- Place
- Williamsport, AK
- Injuries
- 4 uninjured
- Damage
- Substantial damage
- Phase of flight
- Enroute
- Aircraft
- N1075GBell 206B3
- Weather
- Visual (VMC) · Day
- Status
- Completed · report December 30, 1992
- Report
- Approved by Office Director
- NTSB office
- Alaska Regional Office
- FAA report
- 19900421010399A
- Case key
- 5358
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
The manufacturer's inadequate part design and the improper maintenance techniques by the operator.
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 helicopter pilot reported a total loss of power and a subsequent hard autorotation landing. An examination of the engine disclosed a fractured pc tube from the compressor to the pc filter. Failure of this tube will cause the engine to lose power below idle or flame out. An NTSB metallurgist who examined the tube believes that the tube fractured due to fretting and fatigue, most likely precipitated by misalignment of the pc tube during field maintenance. Allison, the engine manufacturer, has recently redesigned the tube with a thicker wall and a different shape to facilitate maintenance procedures in the field, and to make the tube more resistant to fatigue.
Aircraft
- Registration
- N1075G
- Reported as
- Bell 206B3
- Category
- Helicopter
- Serial number
- 2958
- Engine
- Allison 250-C20B, 420 horsepower, turbo shaft
- Damage
- Substantial damage
- Flight
- Part 135
- Registered owner
- Maritime Helicopters
- Airworthiness certificate
- Standard, Normal
- Last inspection
- Annual · April 14, 1990 · 20 hours before
- Departed
- HOM · Homer, AK
- Destination
- HOM · Homer, AK
- Flight plan
- VFR
- Airport
- NONE · Iliamna Bay
Flight crew
As NTSB recorded them. NTSB leaves out names.
- Role
- Pilot
- Age
- 43
- Certificates
- Airline transport, Flight instructor, Commercial
- Airplane ratings
- Single-engine sea, Multi-engine land, Single-engine land
- Instrument ratings
- Helicopter, Airplane
- Medical
- Class 1, Valid Medical--no waivers/lim.
- Seat
- Right
- Flight hours
- 7,069 total · 600 in this make and model · 6,626 as pilot in command · 146 in the last 90 days · 146 in the last 30 days · 5 in the last 24 hours
Weather
- Conditions
- Visual (VMC) · Day
- Wind
- 115° at 10 knots, gusting 5
- Visibility
- 100 statute miles
- Lowest ceiling
- None
- Temperature
- 39 °F
FAA reports on this event · 1
The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.