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December 8, 1985 · Mooney M20E · N5516Q

Selma, CA

Overview

Report Status
Preliminary report
Event Type
Accident
Date
December 8, 1985
Injury Outcomes
No injuries (1 uninjured)
Location
Selma, CA
Aircraft
Mooney M20E
Tail Number
N5516Q
Injuries
None
Aircraft Damage
Substantial
NTSB Number
LAX86LA059

DURING CRUISE ON A VFR X-COUNTRY FLT, THE PLT STATED THAT THE ENG BECAME ROUGH WITH MODERATE VIBRATION LEVELS. AFTER SHUTTING DOWN THE ENG, THE PLT MADE A FORCED LANDING IN A FLD, COLLIDED WITH GND OBSTRUCTIONS & COLLAPSED ALL 3 LANDING GEAR. EXAMINATION OF THE ENG REVEALED THAT THE NUTS ON THE HOLD DOWN STUDS FOR THE #3 CYLINDER HAD BACKED OFF WHICH OVERSTRESSED THE REMAINING NUTS & CAUSED THEM TO FAIL. THE #3 CYLINDER WAS FOUND SEPARATED FROM THE CASE. ACCORDING TO THE IA WHO EXAMINED THE ENG, THE NUTS ON THE NUMBERS 3 & 4 CYLINDERS WERE UNDERTORQUED DURING A PRIOR MAINTENANCE PERIOD. THE IMPROPER TORQUE LEVELS ALLOWED SOME OF THE NUTS TO LOOSEN & EVENTUALLY BACK OFF, PRECIPITATING THE SEQUENCE OF EVENT.

Full Narrative

DURING CRUISE ON A VFR X-COUNTRY FLT, THE PLT STATED THAT THE ENG BECAME ROUGH WITH MODERATE VIBRATION LEVELS. AFTER SHUTTING DOWN THE ENG, THE PLT MADE A FORCED LANDING IN A FLD, COLLIDED WITH GND OBSTRUCTIONS & COLLAPSED ALL 3 LANDING GEAR. EXAMINATION OF THE ENG REVEALED THAT THE NUTS ON THE HOLD DOWN STUDS FOR THE #3 CYLINDER HAD BACKED OFF WHICH OVERSTRESSED THE REMAINING NUTS & CAUSED THEM TO FAIL. THE #3 CYLINDER WAS FOUND SEPARATED FROM THE CASE. ACCORDING TO THE IA WHO EXAMINED THE ENG, THE NUTS ON THE NUMBERS 3 & 4 CYLINDERS WERE UNDERTORQUED DURING A PRIOR MAINTENANCE PERIOD. THE IMPROPER TORQUE LEVELS ALLOWED SOME OF THE NUTS TO LOOSEN & EVENTUALLY BACK OFF, PRECIPITATING THE SEQUENCE OF EVENT.

Flight

Event TypeAccident
Event Time15:20 PST
Nearest Airport0nm N
Runway0
Runway Length0
Runway Width0
Flight Plan FiledNone
Aircraft FireNo
Aircraft ExplosionNo

Aircraft

AircraftMooney M20E
Tail NumberN5516Q
Aircraft CategoryAir
DamageSubstantial
Operating RulePart 91
Engines1
Engine TypeReciprocating
Engine DetailsLycoming · IO-360-A1A · Reciprocating · 200
Seats4

People & Injuries

Injury SummaryNo injuries (1 uninjured)
Fatal0
Serious0
Minor0
Uninjured1
Total1
Crew 1Age 46 · Third Class

Conditions

ConditionsVMC
LightDaylight
Wind360° @ 4 kt
Visibility7 sm
CeilingOvercast 3000 ft
Temperature / Dew Point54 / 0 C
Altimeter30.00 inHg
Observation Time22:54
Weather SourceWFAC

Appendix: Source Data