Bell 204-B accident near Calderwood, Tennessee, April 16, 1997
On April 16, 1997 at about 7:50 pm local time, a Bell 204-B (helicopter), registered N4580Y, was destroyed in an accident near Calderwood, Tennessee. It was a public-use flight under general aviation rules (Part 91). 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
The inadequate maintenance inspection of the helicopter resulting in loss of lubrication from the main drive shaft going undetected until failure of the drive shaft.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 16, 1997 · about 7:50 pm local time
- Place
- Calderwood, Tennessee · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell 204-B · all 204-Bs on the register
- Registration
- N4580Y · no longer on the register · serial 2066
- Damage
- Destroyed
- Flight
- Public-use flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The main drive failed at the transmission end resulting in loss of transmission drive. The pilot performed a autorotation landing in trees and the helicopter rolled inverted and descended through the trees coming to rest on a river bank. Metallurgical examination showed the main drive shaft teeth had separated at the transmission end due to wear from frictional overheating which is a result of loss of lubrication. The helicopter manufacturer instructions require that the main drive shaft be inspected by a mechanic for loss of lubrication and signs of overheating during a daily inspection before the first flight of each day. The operator did not have records to show that the daily inspection had been performed prior to the accident flight.
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: 11,700 hours in all; 1,900 in this make and model; 50 in the last 90 days; 20 in the last 30 days; 11,300 as pilot in command
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 6,645 hours
- Last inspection: annual inspection, January 13, 1997; 80 hours since
- Maximum gross weight: 9,500 lb
- Seats: 6
- Landing gear: fixed
- Engine: Lycoming T-53 (turboshaft); 0 hours total
- Fire on the ground
- Operator: U.S. Forest Svc./State Of Tn.
The flight
- Departed from: 1A3 Copperhill TN at 7:00 pm
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 230° at 12 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 70°F (21°C), dew point 37°F (3°C)
- Altimeter: 30.00 inHg
- Observation at 7:53 pm from TYS, 25 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 N4580Y 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.