# NTSB LAX91LA090: Riddell Lancair 235, N17S, Agua Caliente, CA, February 1, 1991

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Limited investigation · Final report
- Date: February 1, 1991, 12:30 local (20:30 UTC)
- Place: Agua Caliente, CA
- Coordinates: 32.789661, -116.959495 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=32.7897&lon=-116.9595&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 2 serious
- Status: Completed, report March 31, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 27107
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX91LA090
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/27107/pdf
- Page: https://openairdocs.org/ntsb/LAX91LA090

## Probable cause

THE FAILURE OF THE PROPELLER BLADES DUE TO A WEAKENING OF THE WOOD STRUCTURE DUE TO ACID HYDROLYSIS.  A FACTOR IN THE ACCIDENT WAS THE INADEQUATE MAINTENANCE OF THE PROPELLER ASSEMBLY BY ALLOWING EXPOSURE TO EXCESSIVE MOISTURE AND HEAT.

## Sequence of events

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

- Airframe/component/system failure/malfunction, climb - to cruise
  - propeller system/accessories,blade - delamination (cause)
  - propeller system/accessories,blade - failure,total (cause)
  - maintenance,service of aircraft/equipment - inadequate, other maintenance personnel (contributing factor)
- Forced landing, descent - emergency

## Analysis

THE AIRCRAFT WAS ON CLIMB OUT WHEN A LOUD BANG WAS HEARD, FOLLOWED BY AN ENGINE OVERSPEED THEN ENGINE STOPPAGE.  AFTER THE FORCED LANDING, THE PILOTS FOUND THAT BOTH WOODEN PROPELLER BLADES HAD SEPARATED FROM THE STEEL HUB ASSEMBLY.  THE PROPELLER HUB WAS REMOVED FROM THE ENGINE AND SENT TO THE MANUFACTURER FOR FUNCTIONAL ANALYSIS AND DISASSEMBLY UNDER THE SUPERVISION OF FAA INSPECTORS.  THE MANUFACTURER STATED THAT ALL INTERNAL COMPONENTS WERE FUNCTIONAL, HOWEVER, THE CAM ADJUSTMENT FOR THE HIGH AND LOW PITCH STOP SETTINGS HAD BEEN ALTERED FROM THE FACTORY SETTINGS. THE BLADE BUTT ENDS RETAINED IN THE HUB WERE REMOVED AND SUBMITTED TO THE FOREST PRODUCTS LABORATORY OF THE US DEPARTMENT OF AGRICULTURE FOR ANALYSIS.  ACCORDING TO THE LABORATORY THE WOODEN BLADES FRACTURED AND SEPARATED DUE TO A HYDROLYSIS INTERACTION BETWEEN THE WOOD AND THE ADHESIVE CAUSED BY EXCESS MOISTURE AND HEAT.  THE HYDROLYSIS IS A CHEMICAL DECOMPOSITION PROCESS OF THE WOOD AND GLUE RELATIONSHIP.

## Aircraft

- Registration: [N17S](https://openairdocs.org/deregistered/N17S-1992-05-15), registration cancelled 1992-05-15, S/N OJ1988 (OpenAirDocs)
- Reported make and model: RIDDELL LANCAIR 235 (LANCAIR 23)
- Registry model: [Riddell Orin J L 320](https://openairdocs.org/model/riddell-orin-j-l-320) (registry code 05616BK) (OpenAirDocs)
- Category: Airplane, amateur-built
- Serial number: OJ-1988
- Engines: LYCOMING O-320 160 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: Kenneth E. Parks
- Registered owner: Kenneth E. Parks
- Last inspection: Unknown, January 2, 2000
- Departed: MYF, SAN DIEGO, CA

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 47; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; flight hours: 1,500 total, 400 in this make and model, 4,500 as pilot in command

## Weather

- Conditions: Visual (VMC), Day
- Wind: 90° at 15 knots
- Visibility: 10 statute miles
- Lowest ceiling: none

## 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 19910201003529A](https://openairdocs.org/incident/19910201003529A), Feb 1, 1991: Amtrnc 235LANCAIR, Auga Caliente, CA, Substantial damage. Loud bang on takeoff. Engine overspeed and quit. Both wood prop blades separated. Hydrolysis action of wood and glue

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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