# NTSB LAX87DVG06: Ayres S-2R, N4216X, Williams, CA, May 6, 1987

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Final report
- Date: May 5, 1987, 19:15 local (May 6, 1987, 02:15 UTC)
- Place: Williams, CA
- Coordinates: 39.109085, -122.270927 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=39.1091&lon=-122.2709&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor
- Status: Completed, report November 29, 1988
- Report: Approved by Office Director
- NTSB case key (mKey): 25343
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX87DVG06
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/25343/pdf
- Page: https://openairdocs.org/ntsb/LAX87DVG06

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, maneuvering - aerial application
  - propeller system/accessories,counterweight - failure,total (cause)
- Forced landing, descent - emergency
- Nose over, landing - flare/touchdown
  - terrain condition - dirt bank/rising embankment (contributing factor)

## Analysis

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.

## Aircraft

- Registration: [N4216X](https://openairdocs.org/deregistered/N4216X-2000-03-23), registration cancelled 2000-03-23, S/N 1973R (OpenAirDocs)
- Reported make and model: Ayres S-2R
- Registry model: [Rockwell International S-2R](https://openairdocs.org/model/rockwell-international-s-2r) (registry code 7630202) (OpenAirDocs)
- Category: Airplane
- Serial number: 1973R
- Airframe hours: 6616
- Engines: P&W R-1340-AN-1 600 horsepower reciprocating
- Damage: Substantial damage
- Flight: Aerial application, Part 137
- Operator: Robert B. Caldwell, doing business as Caldwell Flying Service
- Registered owner: Robert B. Caldwell
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: Annual, April 26, 1987, 79 hours before

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 36; commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: center; flight hours: 5,165 total, 5,029 in this make and model, 5,809 as pilot in command, 174 in the last 90 days, 55 in the last 30 days, 10 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 15 statute miles
- Lowest ceiling: none
- Temperature: 91 °F, dew point 54 °F
- Altimeter: 29.00 inHg
- Observed at: MVY, 30 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 (OpenAirDocs).

- [Accident 19870505012349A](https://openairdocs.org/incident/19870505012349A), May 5, 1987: Ayres S2RRESTD, Williams, CA, Substantial damage. Engine malfunction on climbout. Stalled. Struck the ground. Hit a levee. Flipped over on its back.

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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