Aircraft Accident/Incident Report

Stockton, California 95201
Thursday, April 4, 1991 19:40 PST

NTSB Narrative Summary Released at Completion of Accident

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.

NTSB Probable Cause Narrative

THE INSTALLATION BY MAINTENANCE PERSONNEL OF AN INCORRECT GASKET THAT RESULTED IN THE LOSS OF THE ENGINE MAGNETO.

Event Information

Type of Event Accident
Event Date 4/4/1991
Event Day of the Week Thursday
Time of Event 1940
Event Time Zone Pacific Standard Time
Event City STOCKTON
Event State CALIFORNIA
Event Country --
Zipcode of the event site 95201
Event Date Year 1991
Event Date Month 4
MidAir Collision Indicator No
On Ground Collision occurred ? No
Event Location Latitude
Event Location Longitude
Event Location Airport
Event Location Nearest Airport ID
Indicates whether the acc/inc occurred off or on an airport Off Airport/Airstrip
Distance from airport in statute miles 0
Degrees magnetic from airport 0
Airport Elevation --
Weather Briefing Completeness Not pertinent
Investigator's weather source Weather Observation Facility
Time of the weather observation 1935 Pacific Standard Time
Direction of event from weather observation facility (degrees) 290
Weather Observation Facility ID SCK
Elevation of weather observation facility 30
Distance of event from weather observation facility (units?) 6
Time Zone of the weather observation PST
Lighting Conditions Night/Dark
Lowest Ceiling Height 0
Lowest Non-Ceiling Height 25000
Sky/Lowest/Cloud Conditions Scattered
Sky Condition for Lowest Ceiling None
Visibility Runway Visual Range (Feet) 0
Visibility Runway Visual Value (Statute Miles) 0
Visibility (Statute Miles) 30
Air Temperature at event time (in degrees celsius) 18
Dew Point at event time (in degress fahrenheit) 7
Wind Direction (degrees magnetic) 270
Variable Wind Indicator Unknown
Wind Speed (knots) 8
Wind Velocity Indicator Unknown
Wind Gust Indicator Unknown
Wind Gust (knots) 0
Altimeter Setting at event time (in. Hg) 30
Density Altitude (feet) --
Intensity of Precipitation Unknown
METAR weather report --
Event Highest Injury None
On Ground, Fatal Injuries 0
On Ground, Minor Injuries 0
On Ground, Serious Injuries 0
Injury Total Fatal --
Injury Total Minor --
Injury Total None 2
Injury Total Serious --
Injury Total All --
Investigating Agency NTSB
NTSB Docket Number (internal use) 1120
NTSB Notification Source --
NTSB Notification Date --
NTSB Notification Time 0
Fiche Number and/or location -used to find docket information 44132
Date of most recent change to record Dec 12 2000 9:44AM
User who most recently changed record dbo
Basic weather conditions Visual Meteorological Cond
FAA District Office --

Aircraft Involved

Aircraft #1

Aircraft Registration Number N733MQ
NTSB Number LAX91LA157
Missing Aircraft Indicator N
Federal Aviation Reg. Part Part 91: General Aviation
Type of Flight Plan filed IFR
Flight plan Was Activated? --
Damage Substantial
Aircraft Fire None
Aircraft Explosion None
Aircraft Manufacturer's Full Name CESSNA
Aircraft Model 172N
Aircraft Series Identifier 172N
Aircraft Serial Number 17268400
Certified Max Gross Weight 2300
Aircraft Category Airplane
Aircraft Registration Class U.S. Registered/U.S. Soil
Aircraft is a homebuilt? No
Flight Crew Seats --
Cabin Crew Seats --
Passenger Seats --
Total number of seats on the aircraft 4
Number of Engines 1
Fixed gear or retractable gear Fixed
Aircraft, Type of Last Inspection Annual
Date of Last Inspection Sep 14 1990 12:00AM
Airframe hours since last inspection 230
Airframe Hours 5600
ELT Installed Yes
ELT Activated Yes
ELT Aided Location of Event Site Unknown
ELT Type --
Aircraft Owner Name KEN GOTTFREDSON
Aircraft Owner Street Address 164 HEATHER LANE
Aircraft Owner City PALO ALTO
Aircraft Owner State CA
Aircraft Owner Country
Aircraft Owner Zipcode 94303
Operator is an individual? --
Operator Name WEST VALLEY FLYING CLUB INC.
Operator Same as Owner? No
Operator Is Doing Business As --
Operator Address Same as Owner? No
Operator Street Address 1901 EMBARCADERO RD. SU 100
Operator City PALO ALTO
Operator State CA
Operator Country
Operator Zip code 94303
Operator Code
Owner has at least one certificate None
Other Operator of large aircraft? No
Certified for Part 133 or 137 Operation Unknown
Operator Certificate Number --
Indicates whether an air carrier operation was scheduled or not --
Indicates Domestic or International Flight --
Operator carrying Pax/Cargo/Mail --
Type of Flying (Per_Bus / Primary) Instructional
Second Pilot on Board Yes
Departure Point Same as Event No
Departure Airport Code PAO
Departure City PALO ALTO
Departure State CA
Departure Country
Departure Time 1850
Departure Time Zone PST
Destination Same as Local Flt --
Destination Airport Code SCK
Destination City STOCKTON
Destination State CA
Destination Country
Specific Phase of Flight Cruise
Report sent to ICAO? --
Evacuation occurred --
Date of most recent change to record Jan 2 2001 10:30AM
User who most recently changed record dbo
Since inspection or accident --
Event Location Runway Number and Location 0
Runway Length --
Runway Width --
Sight Seeing flight No
Air Medical Flight No
Medical Flight --