Bell 47-G3B1 accident near Harwich, Massachusetts, April 20, 1991
On April 20, 1991 at about 12:00 pm local time, a Bell 47-G3B1 (helicopter), registered N1166W, was substantially damaged in an accident near Harwich, Massachusetts. It was an aerial application (crop spraying) flight under agricultural flying rules (Part 137). 1 person had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
A FAILURE OF THE CLUTCH DURING TAKEOFF DUE TO IMPROPER MAINTENANCE PROCEDURES. FACTORS RELATED TO THE ACCIDENT WERE INSUFFICIENT ALTITUDE TO ESTABLISH AN AUTOROTATION.
Source: NTSB aviation accident database, copy made November 2, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 20, 1991 · about 12:00 pm local time · cases in 1991
- Place
- Harwich, Massachusetts
- Type
- Accident
- Injuries
- 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell 47-G3B1 · all 47-G3B1s on the register
- Registration
- N1166W · registry record · serial 2055
- Damage
- Substantial damage
- Flight
- Aerial application (crop spraying) flight · agricultural flying rules (Part 137)
The NTSB's narrative final · quoted from the NTSB record
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.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
Pilot
- Certificate: commercial pilot
- Ratings: single-engine land; rotorcraft: helicopter
- Flight time: 4,240 hours in all; 2,500 in this make and model
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: unk
The aircraft
- Last inspection: inspection type not recorded, January 2, 2000
- Maximum gross weight: 2,950 lb
- Seats: 3
- Landing gear: fixed
- Engine: Lycoming TVO-435-B1A (piston); 0 hours total
- Operator: Firefly Leasing, INC.
The flight
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 020° at 6 knots
- Visibility: 20 statute miles
- Sky: scat
- Temperature: 45°F (7°C), dew point 34°F (1°C)
- Altimeter: 30.00 inHg
- Observation at 11:45 am from HYA, 10 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Other NTSB records under N1166W the same tail number, which may have belonged to a different aircraft at the time
Connections how this case links to the rest of the register
- N1166W on the register today · the tail number may have moved to another aircraft since
- Bell 47 478 registered today · the model family and its accident history
- Bell 3,080 aircraft on the register
- Engine: Lycoming TVO-435-B1A 2 aircraft carry this series today · as the NTSB recorded it
- Accidents and incidents in Massachusetts 987 since 1982 · 90 in the last ten years
- Massachusetts 2,646 aircraft registered
- Other NTSB records under N1166W 1 records · the number may have belonged to another aircraft at the time
The whole map of how records connect · these connections as data: /graph/accident/NYC91DNA02.json.
The bigger picture in Aviation Analytics: accidents over time since 1982, by model, by phase of flight and conditions, by place and on the map.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text does not name anyone involved, its policy at this time. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.