Bell 407 incident near Madera, California, February 19, 2004
On February 19, 2004 at about 11:20 pm local time, a Bell 407 (helicopter), registered N601MT, suffered minor damage in an incident near Madera, California (Madera Municipal airport). It was an instructional flight under general aviation rules (Part 91). No one was hurt; 2 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
the failure of the number 6 hangar bearing due to overheating. A factor in the accident was the operator's likely inadequate compliance with service bulletins and airworthiness directives on this issue, along with an inadequate maintenance inspection program for the bearings.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- February 19, 2004 · about 11:20 pm local time
- Place
- Madera, California · Madera Municipal · map
- Type
- Incident
- Injuries
- No one was hurt; 2 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell 407 · all 407s on the register
- Registration
- N601MT · registry record · serial 53428
- Damage
- Minor damage
- Flight
- Instructional flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot executed an autorotative emergency landing following the failure of the number 6 tail rotor drive shaft hangar bearing while maneuvering. The check pilot and pilot were maneuvering the helicopter when it shuddered momentarily, followed by a heavier airframe vibration. The helicopter rolled left as it climbed to 500 feet. The check pilot attempted to turn right towards the airport; however, the helicopter rolled to the left again. The check pilot regained control, shut the engine down, and completed an autorotation to a field. The tail rotor drive shaft coupling was supported by the aft hangar bearing, and inspection revealed that it had sheared in torsional overload due to an overheated and seized number 6 hangar bearing. Post accident examination revealed that the hangar bearing inner race and the balls had large heat affected zones from overheating during operation (the metal in the races ball path had been molten and then had resolidified). The grease was also black and dry, with imbedded metal particles. A series of service bulletins, alert service bulletins, and airworthiness directives (including an emergency AD issued by the FAA) had been issued beginning in October 2001 through 2004 concerning the overheating and failure of the hangar bearings. The bulletins and airworthiness directives dealt with, in part, the modification of the helicopter to include cooling ducts and changes to existing bearings to prevent overheating and eventual bearing failure. The ADs mandated inspections of the hangar bearings every 25 hours of flight; bearing replacement before further flight was called out if metal particles or "black" grease was observed at any bearing.
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 (unmanned)
- Certificate: commercial pilot
- Ratings: instrument: helicopter; rotorcraft: helicopter
- Flight time: 6,192 hours in all; 140 in this make and model; 34 in the last 90 days; 14 in the last 30 days; 5,420 as pilot in command; 1,820 on instruments
- Last flight review: April 17, 2003
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: left
- Injury: no injuries
Pilot
- Certificate: airline transport pilot, commercial pilot
- Ratings: multi-engine land; single-engine land; instrument: airplane; instrument: helicopter; rotorcraft: helicopter
- Flight time: 5,560 hours in all; 4,500 as pilot in command
- Last flight review: December 2, 2003
- Medical certificate: Class 1 (valid medical--no waivers/lim.)
- Seat: rgt
- Injury: no injuries
The aircraft
- Airframe total time: 1,681.3 hours
- Last inspection: continuous airworthiness programme, January 29, 2004; 34.2 hours since
- Maximum gross weight: 5,250 lb
- Seats: 5
- Landing gear: fixed
- Engine: Allison 250 C47B (turboshaft); 0 hours total
The flight
- Departed from: Madera CA at 10:00 pm
- Flight plan: none
- Runway 120, 5,544 ft by 150 ft
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: at 3 knots
- Visibility: 8 statute miles
- Sky: clear
- Temperature: 55°F (13°C), dew point 46°F (8°C)
- Altimeter: 30.12 inHg
- Observation at 11:53 pm from MAE, 1 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 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.