Bell 407 accident near San Antonio, Texas, November 3, 2015
On November 3, 2015 at about 1:23 am local time, a 1999 Bell 407 (helicopter), registered N496AE, was substantially damaged in an accident during maneuvering (hover) near San Antonio, Texas (San Antonio International airport). It was flown under charter and air-taxi rules (Part 135). No one was hurt; 3 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 No. 3 tail rotor adapter and shaft due to a loss of torque on the retaining nut. Contributing to the accident was the lack of a requirement to inspect the tail rotor assembly for security in the helicopter manufacturer's maintenance manual and the operator's approved aircraft inspection program.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- November 3, 2015 · about 1:23 am local time
- Place
- San Antonio, Texas · San Antonio International · map
- Type
- Accident
- Injuries
- No one was hurt; 3 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell 407, built 1999 · all 407s on the register
- Registration
- N496AE · registry record · serial 53328
- Damage
- Substantial damage
- Flight
- Flight · charter and air-taxi rules (Part 135)
The NTSB's narrative final · quoted from the NTSB record
The commercial pilot was conducting an emergency medical services flight. The pilot reported that, when he climbed the helicopter to a 3-ft hover, he heard a loud bang, and the helicopter began an uncommanded right yaw. The pilot applied full left pedal, but this did not arrest the yaw. The pilot then lowered the collective, and the helicopter touched down and then rotated 270 degrees to the right before it came to a stop. The tail rotor was examined, and it could be manually rotated, but a grinding noise could be heard coming from the damaged No. 3 hanger bearing. The main rotor blades did not rotate in synchronization with the tail rotor blades. The No. 3 tail rotor shaft adapter and shaft splines were completely ground down, the adapter and shaft had failed, and there was evidence of excessive torsion beyond the intended allowable tolerances. The aluminum adapter washer hole was elongated, consistent with a loose through bolt, and the drive shaft through bolt had worn threads. There was a 1/8-inch gap between the adapter and the base of the hanger bearing, consistent with the adapter not being fully in contact with the bearing and potential stress within the adapter and shaft splines. The retaining nut had migrated almost .025 inch outward and was very loose, consistent with the loss of torque, which would have allowed movement between the tail rotor adapter and shaft and led to their eventual failure. A review of the helicopter maintenance manual and operator's approved aircraft inspection program revealed that neither had a requirement for the tail rotor assembly to be inspected for security.
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
What happened, in order
- Aircraft structural failure during maneuvering (hover) defining event
The NTSB's findings
- cause Aircraft › Aircraft propeller/rotor › Tail rotor drive system › Tail rotor drive shaft › Fatigue/wear/corrosion
- cause Aircraft › Aircraft propeller/rotor › Tail rotor drive system › Tail rotor drive shaft › Failure
- factor Organizational issues › Management › Policy/procedure › Adequacy of policy/proc › Manufacturer
- factor Organizational issues › Management › Policy/procedure › Adequacy of policy/proc › Operator
Pilot
- Certificate: commercial pilot
- Ratings: instructor: instrument helicopter; instrument: helicopter; rotorcraft: helicopter
- Flight time: 2,201 hours in all; 28 in this make and model; 97 in the last 90 days; 2,626 in the last 30 days; 1,207 as pilot in command
- Last flight review: October 15, 2015
- Medical certificate: Class 1 (without waivers/limitations)
- Seat: rgt
- Injury: no injuries
The aircraft
- Airframe total time: 7,939 hours
- Last inspection: approved inspection programme, November 2, 2015
- Maximum gross weight: 5,250 lb
- Seats: 4
- Landing gear: fixed
- Engine: Rolls Royce M250-C47B (turboshaft); 4,162 hours total
- Operator: Air Evac Ems, Inc.
The flight
- Departed from: KSAT San Antonio TX at 1:23 am
- Destination: XS83 San Antonio TX
Weather at the time
- Light: night
- Wind: from 130° at 5 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 70°F (21°C), dew point 54°F (12°C)
- Altimeter: 29.95 inHg
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight 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.