Bell 47G-2A accident near Porterville, California, July 20, 2003
On July 20, 2003 at about 8:30 am local time, a Bell 47G-2A (helicopter), registered N4774S, was substantially damaged in an accident near Porterville, California. It was an aerial application (crop spraying) flight under agricultural flying rules (Part 137). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
Fatigue-induced failure of bolts in the helicopter's rotor drive flange, which resulted in a total loss of torque to the rotor drive shaft.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 20, 2003 · about 8:30 am local time
- Place
- Porterville, California · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell 47G-2A · all 47G-2As on the register
- Registration
- N4774S · no longer on the register · serial WAV182
- Damage
- Substantial damage
- Flight
- Aerial application (crop spraying) flight · agricultural flying rules (Part 137)
The NTSB's narrative final · quoted from the NTSB record
During an agricultural spray flight, when the helicopter's drive system disconnected from the engine, the helicopter yawed and descended about 10 feet into the underlying cotton field. The helicopter rolled upon impacting the uneven terrain. Prior to the event, the pilot heard the transmission make a loud noise and the engine oversped. The helicopter's drive system was examined, and 12 bolts on the planetary gear flange were found broken due to fatigue.
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: flight instructor, commercial pilot
- Ratings: single-engine land; instructor: helicopter; rotorcraft: helicopter
- Flight time: 5,500 hours in all; 3,000 in this make and model; 120 in the last 90 days; 30 in the last 30 days; 5,400 as pilot in command; 1,000 on instruments
- Last flight review: January 5, 2003
- Medical certificate: Class 2 (valid medical--no waivers/lim.)
- Seat: ctr
- Injury: no injuries
The aircraft
- Airframe total time: 2,800 hours
- Last inspection: annual inspection, July 17, 2002; 78 hours since
- Maximum gross weight: 2,850 lb
- Landing gear: fixed
- Engine: Lycoming VO-435-A1F (piston); 0 hours total
The flight
- Departed from: Porterville CA at 7:00 am
- Destination: Porterville CA
- Flight plan: none
Weather at the time
- Light: night, dark
- Wind: from 140° at 6 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 75°F (24°C), dew point 59°F (15°C)
- Altimeter: 29.90 inHg
- Observation at 10:15 am from PVT, 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 N4774S the same tail number, which may have belonged to a different aircraft at the time
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.