- Date
- June 25, 1997, 12:43 local (19:43 UTC)
- Place
- Riverside, CA
- Injuries
- 3 minor
- Damage
- Substantial damage
- Phase of flight
- Enroute
- Aircraft
- N99YCEnstrom F-28-F
- Weather
- Visual (VMC) · Day
- Status
- Completed · report February 2, 1998
- Report
- Approved by Office Director
- FAA report
- 19970625040829A
- Case key
- 29821
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 by unknown maintenance personnel to retorque the nuts on the retainer cover.
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 takeoff, the helicopter lost power and landed hard. Postaccident examination revealed the No. 2 cylinder intake valve rocker shaft migrated out of the shaft bosses of the cylinder head. The shaft, cover, and nuts were found; the washers were not. According to owner/pilot there were internal star washer imprints on the cover plate commonly caused by torque or tightening of the nut. The helicopter had 61.5 total hours since new, and received one 50-hour inspection since delivery to the owner/pilot. The owner/pilot changed the oil and filter just prior to the inspection.
Factual narrative
On June 25, 1997, at 1243 hours Pacific daylight time, an Enstrom F-28-F helicopter, N99YC, was substantially damaged after a loss of power during a takeoff/climb at Riverside, California. The pilot and two passengers received minor injuries. Visual meteorological conditions prevailed for the local flight and no flight plan was filed. The flight was destined for Corona Airport, Corona, California.
According to the pilot, the loss of engine power occurred less than 200 feet agl. He attempted an auto rotation and landed hard. Postaccident examination of the engine revealed that the intake valve rocker shaft migrated out of the shaft bosses of the cylinder head. The shaft, cover, and nuts were found; the washers were not. The pilot stated that there were internal star washer imprints on the cover plate that is commonly caused by the torque or tightening of the nut. The helicopter had 61.5 total hours since new and received one inspection at 50.9 hours since delivery to the owner/pilot.
The owner/pilot changed the oil and filter prior to the formal 50-hour inspection by a private contractor. The inspection form revealed no specific inspection of the retainer plates are required except for a general condition inspection of the engine, accessories, and of the fluid systems for leaks.
Aircraft
- Registration
- N99YC
- Reported as
- Enstrom F-28-F
- Category
- Helicopter
- Serial number
- 809
- Airframe hours
- 61
- Engine
- Lycoming HIO-360-F1AD, 205 horsepower, reciprocating
- Damage
- Substantial damage
- Flight
- Personal · Part 91
- Operator
- Stits Aircraft
- Registered owner
- Enstrom Helicopter
- Airworthiness certificate
- Standard, Normal
- Last inspection
- Unknown · May 19, 1997 · 1 hours before
- Departed
- RAL · CA
- Destination
- L66 · Corona, CA
- Airport
- RAL · Riverside Municipal
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
- 76
- Certificate
- Commercial
- Airplane ratings
- Single-engine sea, Multi-engine sea, Single-engine land, Multi-engine land
- Instrument ratings
- Airplane
- Medical
- Class 3, Valid Medical--w/ waivers/lim
- Seat
- Left
- Flight hours
- 2,500 total
Weather
- Conditions
- Visual (VMC) · Day
- Wind
- 300° at 9 knots
- Visibility
- 4 statute miles
- Lowest ceiling
- None
- Observed at
- KRA
FAA reports on this event · 1
The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.