Bell 47D1 accident near Marathon, Florida, April 22, 1994
On April 22, 1994 at about 3:28 pm local time, a Bell 47D1 (helicopter), registered N9660, was destroyed in an accident near Marathon, Florida. It was a flight of an unrecorded kind under general aviation rules (Part 91). 2 people were killed and 1 person was seriously injured. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
SEPARATION OF THE TAIL ROTOR GEARBOX AND TAIL ROTOR BLADES FOR AN UNDETERMINED REASON. FACTORS RELATED TO THE ACCIDENT WERE: FAILURE OF MAINTENANCE PERSONNEL TO FOLLOW THE PROPER MAINTENANCE PROCEDURE AFTER A PREVIOUS TAIL ROTOR STRIKE, AND FAILURE TO CONDUCT A 100-HOUR INSPECTION WHEN DUE.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 22, 1994 · about 3:28 pm local time
- Place
- Marathon, Florida · map
- Type
- Accident
- Injuries
- 2 people were killed and 1 person was seriously injured.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell 47D1 · all 47D1s on the register
- Registration
- N9660 · no longer on the register · serial 486
- Damage
- Destroyed
- Flight
- Flight of an unrecorded kind · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
WITNESSES HEARD A LOUD NOISE AS THE HELICOPTER WAS FLYING AT 100' TO 150' AGL & SAW SOMETHING FALL FROM THE TAIL BOOM. THE HELICOPTER IMMEDIATELY NOSED DOWN & BEGAN SPINNING TO THE RIGHT. IT IMPACTED ON A ROCK ISLAND & CAME TO REST IN WATER NEXT TO THE ISLAND. THE TAIL ROTOR GEARBOX, TAIL ROTOR HUB & ONE TAIL ROTOR BLADE WERE NOT LOCATED AFTER THE ACCIDENT. ONE TAIL ROTOR BLADE WAS FOUND ALONG THE FLIGHTPATH IN 2 PIECES, ABOUT 150' FROM THE MAIN WRECKAGE. THE TAIL ROTOR GEARBOX HAD SEPARATED DUE TO OVERSTRESS; ALL FRACTURES OF THE RECOVERED TAIL ROTOR BLADE WERE TYPICAL OF OVER- STRESS. THE TAIL ROTOR BLADE HAD NO IMPACT MARKS ON THE LEADING EDGE OR TIP. NO PRECRASH FAILURE/MALFUNCTION OF THE REMAINING STRUCTURE, FLIGHT CONTROLS, MAIN ROTOR BLADES, TRANSMISSION OR ENGINE WAS FOUND. A TAIL ROTOR STRIKE OCCURRED 130 FLIGHT HRS BEFORE THE ACCIDENT; THE TAIL ROTOR BLADES WERE CHANGED, BUT THE HUB WAS NOT CHANGED AS REQUIRED BY THE MANUFACTURER'S INSTRUCTION. THOUGH OPERATING FOR HIRE, HELICOPTER HAD FLOWN 130 HRS SINCE THE LAST MAINTENANCE INSPECTION. CALCULATIONS SHOWED THAT DURING TAKEOFF, THE HELICOPTER'S CG WAS 3.4' FORWARD OF THE FORWARD LIMIT. WITH LOSS OF THE SEPARATED PARTS, THE CG WOULD HAVE MOVED ABOUT 2' FURTHER FORWARD.
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: instructor: helicopter; rotorcraft: helicopter
- Flight time: 677 hours in all; 93 in this make and model; 93 in the last 90 days; 53 in the last 30 days; 551 as pilot in command; 266 on instruments
- Medical certificate: Class 1 (valid medical--w/ waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 7,502 hours
- Last inspection: approved inspection programme, March 10, 1994; 105 hours since
- Maximum gross weight: 2,350 lb
- Seats: 3
- Landing gear: fixed
- Engine: Franklin 6V4-200-C32 (piston); 0 hours total
The flight
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 170° at 7 knots
- Visibility: 10 statute miles
- Sky: broken clouds at 20,000 ft; scat at 2,000 ft
- Temperature: 84°F (29°C), dew point 75°F (24°C)
- Altimeter: 29.00 inHg
- Observation at 3:52 pm from EYW, 42 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | |||
| Passengers | 2 |
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.
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 never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.