# NTSB LAX91LA359: Benson/Ambrocini/Wentzel B-8MJ, N8241, Turlock, CA, August 15, 1991

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Limited investigation · Final report
- Date: August 15, 1991, 13:20 local (20:20 UTC)
- Place: Turlock, CA
- Coordinates: 37.469642, -120.85041 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=37.4696&lon=-120.8504&mi=10
- Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping)
- Highest injury: Fatal
- Injuries: 1 fatal
- Status: Completed, report March 24, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 27328
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX91LA359
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/27328/pdf
- Page: https://openairdocs.org/ntsb/LAX91LA359

## Probable cause

THE PILOT'S OVER ROTATION OF THE GYROCOPTER DURING THE TAKEOFF SEQUENCE WHICH RESULTED IN A LOSS OF CONTROL. CONTRIBUTING TO THE ACCIDENT WAS THE POOR MAINTENANCE PRACTICES PERFORMED ON THE MACHINE.

## Sequence of events

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

- Loss of control - in flight, takeoff - initial climb
  - flight controls - improper use of, pilot in command (cause)
  - rotation - excessive, pilot in command (cause)
  - aircraft control - not maintained, pilot in command (cause)
  - maintenance - poor, pilot in command (contributing factor)
- On ground/water collision with object, landing - roll
  - aborted takeoff - attempted, pilot in command
  - object - vehicle

## Analysis

THE NON HELICOPTER RATED PILOT WAS USING AN UNAPPROVED TAKEOFF AND LANDING AREA BETWEEN HANGERS ON THE AIRPORT. NUMEROUS MAINTENANCE AND CERTIFICATION IRREGULARITIES WERE FOUND.  THE GYROCOPTER HAD NOT HAD AN ANNUALLY REQUIRED CONDITION INSPECTION SINCE 1986. NUMEROUS GROUND WITNESSES REPORTED THAT AFTER THE PILOT COMPLETED THE MODIFICATIONS, HE MADE ONE ABORTED ATTEMPT TO TAKEOFF.  THE PILOT WAS NEXT SEEN TO TAXI THE GYROCOPTER BACK TO HIS HANGAR WHERE HE MADE SOME MINOR ADJUSTMENTS TO THE ROTOR SYSTEM.  THE PILOT THEN TAXIED THE AIRCRAFT BACK TO THE ORIGINAL TAKEOFF SPOT, SPUN UP THE ROTOR SYSTEM AND INITIATED ANOTHER TAKEOFF.  THE WITNESSES SAW THE MACHINE LIFT OFF IN A STEEPER THAN NORMAL NOSE HIGH ATTITUDE, THEN THE ROTOR BLADES BEGAN TO WAVE ERRATICALLY 'LIKE SPAGHETTI.'  THE GYROCOPTER HIT THE GROUND ON ITS WHEELS AND ROLLED INTO A PICKUP TRUCK.  THE GYROCOPTER WAS EXAMINED BY AN FAA AIRWORTHINESS INSPECTOR FAMILIAR WITH THE MACHINES.  HE REPORTED THAT HE FOUND NO IDENTIFIABLE PREIMPACT MALFUNCTIONS OR FAILURES.

## Aircraft

- Registration: [N8241](https://openairdocs.org/deregistered/N8241-1993-04-08), registration cancelled 1993-04-08, S/N A1443 (OpenAirDocs)
- Reported make and model: BENSON/AMBROCINI/WENTZEL B-8MJ
- Registry model: [Bensen Gyrocopter B-8MJ](https://openairdocs.org/model/bensen-gyrocopter-b-8mj) (registry code 130070H) (OpenAirDocs)
- Category: Gyroplane, amateur-built
- Serial number: A-1443
- Engines: MCCULLOCH 4318A 71 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: Wentzel, Alfred S.
- Registered owner: Wentzel, Alfred S.
- Airworthiness certificate: Special, Experimental (Special)
- Last inspection: Unknown, January 2, 2000
- Airport: Turlock

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 79; private; airplane ratings: single-engine land; medical: class 3, valid medical--w/ waivers/lim; seat: center; toxicology performed

## Weather

- Conditions: Visual (VMC), Day
- Visibility: 20 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 19910815034419A](https://openairdocs.org/incident/19910815034419A), Aug 15, 1991: Amtrbx BENSEN8M, Turlock, CA, Substantial damage, 1 fatal. Lost control on takeoff. Waivered,descended and struck a truck. No recent homebuilt inspections. Modification made.

## Other investigations on N8241 (1)

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.

- [NTSB OAK70DVD28](https://openairdocs.org/ntsb/OAK70DVD28), Jun 21, 1970: Bensen B-8M (N8241), Tracy, CA, substantial damage

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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