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NTSB Report
May 6, 1987 · Ayres S-2R · N4216X
Williams, CA
Overview
Report Status
Preliminary report
Event Type
Accident
Date
May 6, 1987
Injury Outcomes
1 injury (1 minor injury)
Location
Williams, CA
Aircraft
Ayres S-2R
Tail Number
N4216X
Operator
Robert B Caldwell
Injuries
Minor
Aircraft Damage
Substantial
NTSB Number
LAX87DVG06
THE PLT REPORTED HE HEARD SOMETHING BREAK. THE SOUND WAS FOLLOWED BY A VIBRATION. THE PLT THEN TURNED TO LAND ON A ROAD. HE WAS UNABLE TO MAINTAIN ALT AND AIRSPEED. THE ROCKWELL S2R LANDED IN A CULTIVATED FIELD AND NOSED OVER AFTER A COLLISION WITH A DIRT BANK. POST ACCIDENT EXAM OF THE PROP HUB ASSEMBLY REVEALED THAT THE COUNTERWEIGHT BEARING SHAFT WAS FRACTURED ON ONE OF THE PROP BLADES. THIS WOULD ALLOW ONE PROP BLADE TO ROTATE AT A DIFFERENT PITCH ANGLE. THE ROCKWELL S2R HAD A TWO BLADED HAMILTON STANDARD 12D40-305 PROP INSTALLED. IT HAD BEEN MODIFIED IN ACCORDANCE WITH STC #SP1408NW WHICH REPLACES THE HAMILTON STANDARD COUNTERWEIGHT BEARINGS WITH MIDWEST AVIATION ROLLERS.
Full Narrative
THE PLT REPORTED HE HEARD SOMETHING BREAK. THE SOUND WAS FOLLOWED BY A VIBRATION. THE PLT THEN TURNED TO LAND ON A ROAD. HE WAS UNABLE TO MAINTAIN ALT AND AIRSPEED. THE ROCKWELL S2R LANDED IN A CULTIVATED FIELD AND NOSED OVER AFTER A COLLISION WITH A DIRT BANK. POST ACCIDENT EXAM OF THE PROP HUB ASSEMBLY REVEALED THAT THE COUNTERWEIGHT BEARING SHAFT WAS FRACTURED ON ONE OF THE PROP BLADES. THIS WOULD ALLOW ONE PROP BLADE TO ROTATE AT A DIFFERENT PITCH ANGLE. THE ROCKWELL S2R HAD A TWO BLADED HAMILTON STANDARD 12D40-305 PROP INSTALLED. IT HAD BEEN MODIFIED IN ACCORDANCE WITH STC #SP1408NW WHICH REPLACES THE HAMILTON STANDARD COUNTERWEIGHT BEARINGS WITH MIDWEST AVIATION ROLLERS.
Flight
Event TypeAccident
Event Time19:15 PDT
Nearest Airport0nm W
Runway0
Flight Plan FiledNone
Aircraft FireNo
Aircraft ExplosionNo
Aircraft
AircraftAyres S-2R
Tail NumberN4216X
Aircraft CategoryAir
DamageSubstantial
OperatorRobert B Caldwell
Operating RulePart 137
Engines1
Engine TypeReciprocating
Engine DetailsP&W · R-1340-AN-1 · Reciprocating · 600
Seats1
People & Injuries
Injury Summary1 injury (1 minor injury)
Fatal0
Serious0
Minor1
Uninjured0
Total1
Crew 1Age 36 · Second Class
Conditions
ConditionsVMC
LightDaylight
WindCalm
Visibility15 sm
CeilingNone
Temperature / Dew Point54
Altimeter29.00 inHg
Observation Time01:46
Weather SourceWFAC