# NTSB DEN91FA068: Bell 206B-3, N717NH, Houston, TX, May 7, 1991

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Field investigation · Final report
- Date: May 7, 1991, 13:10 local (18:10 UTC)
- Place: Houston, TX
- Coordinates: 29.770204, -95.310897 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=29.7702&lon=-95.3109&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 2 serious, 2 minor; on the ground: 1 minor
- Status: Completed, report March 24, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 18022
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN91FA068
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/18022/pdf
- Page: https://openairdocs.org/ntsb/DEN91FA068

## Probable cause

ENGINE MOUNT DELAMINATION AND LACK LUBRICATION, CAUSING THE DRIVE SHAFT TO FAIL. POOR SERVICING OF THE HELICOPTER WAS A RELATED FACTOR.

## Sequence of events

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

- Airframe/component/system failure/malfunction, cruise - normal
  - maintenance - inadequate, company maintenance personnel (cause)
  - maintenance,lubrication - inadequate, company maintenance personnel (cause)
  - engine installation,suspension mounts - delamination (cause)
  - turboshaft engine,power output shaft - failure,total (cause)
- Forced landing, descent - emergency
  - autorotation - performed, pilot in command
- In flight collision with object, landing
  - object - residence

## Analysis

WHILE ON A FLIGHT OVER METROPOLITAN HOUSTON TO GET AERIAL VIDEO FOOTAGE, THE MAIN DRIVE SHAFT COUPLING FAILED & THE PILOT WAS FORCED TO MAKE AN AUTOROTATION. HE TRIED TO LAND IN A PARKING LOT, BUT WAS UNABLE TO REACH IT. SUBSEQUENTLY, THE HELICOPTER CRASH LANDED ON THE ROOF OF AN APARTMENT HOUSE. AN INVESTIGATION DISCLOSED THE ENGINE MOUNT WAS OIL SOAKED & HAD DELAMINATED, CAUSING MISALIGNMENT OF THE DRIVE SHAFT. ALSO, A LACK OF LUBRICATION WAS NOTED IN THE MAIN DRIVE SHAFT COUPLING. OTHER MAINTENANCE DISCREPANCIES WERE ALSO NOTED DURING THE INVESTIGATION.

## Aircraft

- Registration: [N717NH](https://openairdocs.org/deregistered/N717NH-1991-08-10), registration cancelled 1991-08-10, S/N 2847 (OpenAirDocs)
- Reported make and model: BELL 206B-3
- Registry model: [Bell 206B](https://openairdocs.org/model/bell-206b) (registry code 1181511) (OpenAirDocs)
- Category: Helicopter
- Serial number: 2847
- Airframe hours: 2966
- Engines: ALLISON 250-C20B 317 horsepower turbo shaft
- Damage: Destroyed
- Flight: Part 135
- Registered owner: Contractors Helicopters
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, October 27, 1990, 98 hours before
- Departed: N/A, HOUSTON, TX

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 57; commercial, flight instructor, airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; seat: right; toxicology performed; flight hours: 8,021 total, 1,415 in this make and model, 7,414 as pilot in command, 62 in the last 90 days, 15 in the last 30 days, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 90° at 8 knots
- Visibility: 7 statute miles
- Lowest ceiling: 1,400 ft broken
- Temperature: 73 °F, dew point 70 °F
- Altimeter: 30.00 inHg
- Observed at: HOU, 9 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 19910507014309A](https://openairdocs.org/incident/19910507014309A), May 7, 1991: Bell 206B3, Houston, TX, Destroyed. Main rotor drive bolts failed. Crashed on apartment roof on forced landing. Shaft was overheated. Poor maintenance.

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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