# NTSB ATL91LA066: Benson B8M, N6572K, Hartselle, AL, March 16, 1991

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Limited investigation · Final report
- Date: March 16, 1991, 14:05 local (20:05 UTC)
- Place: Hartselle, AL
- Coordinates: 34.429634, -86.929107 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=34.4296&lon=-86.9291&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Fatal
- Injuries: 1 fatal
- Status: Completed, report May 5, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 8384
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ATL91LA066
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/8384/pdf
- Page: https://openairdocs.org/ntsb/ATL91LA066

## Probable cause

THE IMPROPER INSTALLATION OF THE MAIN ROTOR BEARING BLOCK BY THE OWNER/PILOT WHICH RESULTED IN THE SEPARATION OF THE MAIN ROTOR SYSTEM.

## Sequence of events

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

- Airframe/component/system failure/malfunction, cruise
  - rotor system - separation (cause)
  - maintenance,installation - improper, pilot in command (cause)
- Loss of control - in flight, cruise
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

WITNESSES STATED THAT THE AIRCRAFT WAS FLYING AT ABOUT 200 FEET ABOVE GROUND LEVEL WHEN THE GYROCOPTER'S MAIN ROTOR SEPARATED FROM THE AIRCRAFT. INVESTIGATION REVEALED THAT THE COMMERCIAL PILOT, WHO WAS NOT RATED IN GYROCOPTER'S HAD BUILT AND DID ALL THE MAINTENANCE ON THE GYROCOPTER. FURTHER INVESTIGATION REVEALED THAT THE RETAINER WASHER WAS MISSING FROM THE MAIN ROTOR BEARING BLOCK ASSEMBLY.

## Aircraft

- Registration: [N6572K](https://openairdocs.org/deregistered/N6572K-2013-10-28), registration cancelled 2013-10-28, S/N S-223 (OpenAirDocs)
- Reported make and model: BENSON B8M
- Registry model: [Spivey Franklin G B8M](https://openairdocs.org/model/spivey-franklin-g-b8m) (registry code 13021SC) (OpenAirDocs)
- Category: Gyroplane, amateur-built
- Serial number: S-223
- Engines: MCCULLOCH 90 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: Spivey, Franklin G.
- Airport: 5MO, Rountree Field

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 54; commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; toxicology performed; flight hours: 9,300 total, 250 in the last 90 days

## Weather

- Conditions: Visual (VMC), Day
- Wind: 80° at 8 knots
- Visibility: 15 statute miles
- Lowest ceiling: 25,000 ft overcast
- Temperature: 64 °F, dew point -0 °F
- Observed at: HSV, 18 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 19910316005439A](https://openairdocs.org/incident/19910316005439A), Mar 16, 1991: Amtr B8M, Brewster, WA, Substantial damage, 1 fatal. Main rotor system departed gyroplane in flight. Impact was near vertical. Builder pilot failed use retainer washer.

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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