# NTSB NYC91DNA02: Bell 47-G3B1, N1166W, Harwich, MA, April 20, 1991

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Final report
- Date: April 20, 1991, 08:00 local (12:00 UTC)
- Place: Harwich, MA
- Location: 41.6862° N, 70.0759° W: Placed by OpenAirDocs: center of Harwich, MA, within about 6 miles (OpenAirDocs)
- Nearby events: https://openairdocs.org/map.md?lat=41.6862&lon=-70.0759&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor
- Status: Completed, report May 7, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 36760
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=NYC91DNA02
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/36760/pdf
- Page: https://openairdocs.org/ntsb/NYC91DNA02

## Probable cause

A FAILURE OF THE CLUTCH DURING TAKEOFF DUE TO IMPROPER MAINTENANCE PROCEDURES.  FACTORS RELATED TO THE ACCIDENT WERE INSUFFICIENT ALTITUDE TO ESTABLISH AN AUTOROTATION.

## Sequence of events

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

- Loss of engine power(partial) - mech failure/malf, maneuvering - aerial application
  - rotor drive system,clutch assembly - worn (cause)
  - maintenance - improper, company maintenance personnel (cause)
- Forced landing, descent - emergency
- Hard landing, landing - flare/touchdown
  - remedial action - not possible, pilot in command (contributing factor)

## Analysis

THE HELICOPTER EXPERIENCED A LOSS OF LIFT THROUGH THE MAIN ROTOR SYSTEM AND MADE A HARD LANDING.  POST CRASH EXAMINATION SHOWED THE CLUTCH HAD RECENTLY BEEN REMOVED AND DISASSEMBLED FOR INSPECTION.  THE CLUTCH WAS RETURNED TO SERVICE WITH ONLY 25 PERCENT SHOE/DRUM CONTACT.  MAINTENANCE PERSONNEL HAD NOT FOLLOWED THE PROCEDURES CONTAINED IN THE OVERHAUL MANUAL.

## Aircraft

- Registration: N1166W (not matched to a registry record)
- Reported make and model: BELL 47-G3B1
- Category: Helicopter
- Serial number: 2055
- Engines: LYCOMING TVO-435-B1A 260 horsepower reciprocating
- Damage: Substantial damage
- Flight: Aerial application, Part 137
- Operator: Firefly Leasing, Inc.
- Registered owner: Firefly Leasing, Inc.
- Airworthiness certificate: Standard, Normal; Special, Restricted (Special)
- Last inspection: Unknown, January 2, 2000
- Airport: NONE

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 35; commercial; airplane ratings: single-engine land; medical: class 2, valid medical--w/ waivers/lim; flight hours: 4,240 total, 2,500 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 20° at 6 knots
- Visibility: 20 statute miles
- Lowest ceiling: none
- Temperature: 45 °F, dew point 34 °F
- Altimeter: 30.00 inHg
- Observed at: HYA, 10 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 19910420011599A](https://openairdocs.org/incident/19910420011599A), Apr 20, 1991: Bell 47G3B1, Harwich, MA, Substantial damage. Rotor rpms decayed and engine overspeed on climbout. Landed hard in cranberry bog. Clutch drum scored and worn out.

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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