- Date
- April 4, 1991, 19:40 local (Apr 5, 1991, 03:40 UTC)
- Place
- Stockton, CA
- Injuries
- 2 uninjured
- Damage
- Substantial damage
- Phase of flight
- Enroute
- Aircraft
- N733MQCessna 172N
- Weather
- Visual (VMC) · Night/dark
- Status
- Completed · report May 3, 1993
- Report
- Approved by Office Director
- FAA report
- 19910404009099A
- Case key
- 27158
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 installation by maintenance personnel of an incorrect gasket that resulted in the loss of the engine magneto.
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 certificated commercial pilot/certified flight instructor and a certificated private pilot/instrument student were in a holding pattern, in VFR conditions, while on an instrument training flight when the engine quit. The CFI made a forced landing in an open field. During the landing roll, the airplane encountered soft terrain and nosed over. Examination of the engine revealed that the magneto assembly fell off the engine. An improper gasket was installed under the magneto housing that prevented the magneto from being properly tightened to the required torque setting. Gasket material under the nut provided a cushion affect that allowed the nut to vibrate loose.
Aircraft
- Registration
- N733MQ
- Reported as
- Cessna 172N
- Category
- Airplane
- Serial number
- 17268400
- Airframe hours
- 5,600
- Engine
- Lycoming O-320-H2AD, 160 horsepower, reciprocating
- Damage
- Substantial damage
- Flight
- Instructional · Part 91
- Operator
- West Valley Flying Club Inc.
- Registered owner
- Ken Gottfredson
- Airworthiness certificate
- Standard, Normal
- Last inspection
- Annual · September 14, 1990 · 230 hours before
- Departed
- PAO · Palo Alto, CA
- Destination
- SCK · Stockton, CA
- Flight plan
- IFR
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
- 27
- Certificates
- Commercial, Flight instructor
- Airplane ratings
- Single-engine sea, Multi-engine land, Single-engine land, Multi-engine sea
- Instrument ratings
- Airplane
- Medical
- Class 1, Valid Medical--w/ waivers/lim
- Seat
- Right
- Flight hours
- 7,000 total · 300 in this make and model · 6,950 as pilot in command · 400 in the last 90 days · 100 in the last 30 days · 7 in the last 24 hours
Weather
- Conditions
- Visual (VMC) · Night/dark
- Wind
- 270° at 8 knots
- Visibility
- 30 statute miles
- Lowest ceiling
- None
- Temperature
- 64 °F, dew point 45 °F
- Altimeter
- 30.00 inHg
- Observed at
- SCK, 6 nm away
FAA reports on this event · 1
The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.