Bell 407 accident near Aberdeen, South Dakota, April 14, 2012
On April 14, 2012 at about 7:55 am local time, a Bell 407 (helicopter), registered N509MT, was substantially damaged in an accident during enroute near Aberdeen, South Dakota. It was a positioning flight under general aviation rules (Part 91). 1 person had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The fatigue failure of two turbine engine blades due to vibration.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 14, 2012 · about 7:55 am local time
- Place
- Aberdeen, South Dakota · map
- Type
- Accident
- Injuries
- 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell 407 · all 407s on the register
- Registration
- N509MT · registry record · serial 53281
- Damage
- Substantial damage
- Flight
- Positioning flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot reported that, shortly after departure, the helicopter yawed left and that he heard a "loud howling/grinding sound" emanating from the upper area of the helicopter. He subsequently reduced power and performed a minimum power descent to an open area. During the landing, the helicopter touched down hard. A postimpact examination of the engine found that two third-stage turbine wheel blades had cracked and separated due to high-cycle fatigue at the trailing edge during operation of one or more natural frequencies of the wheel. Four additional blades displayed fatigue cracks. Metallurgy examinations revealed that the blades had no evidence of material anomalies and met the material hardness and composition specifications. The observed high-cycle fatigue initiation and propagation characteristics were consistent with operating in a condition conducive to vibration. The engine manufacturer plans to release design changes that will increase the operating speed natural frequency margin and improve the vibration margin.
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
- Powerplant sys/comp malf/fail during enroute defining event
- Loss of engine power (partial) during enroute
- Off-field or emergency landing during emergency descent
- Hard landing during landing (flare/touchdown)
The NTSB's findings
- cause Aircraft › Aircraft power plant › Engine (turbine/turboprop) › Turbine section › Fatigue/wear/corrosion
Pilot
- Certificate: commercial pilot
- Ratings: single-engine land; instrument: airplane; instrument: helicopter; rotorcraft: helicopter
- Flight time: 3,790 hours in all; 23 in this make and model; 9 in the last 90 days; 4 in the last 30 days; 2,150 as pilot in command
- Last flight review: April 12, 2012
- Medical certificate: Class 2 (with waivers/limitations)
- Seat: rgt
- Injury: minor injuries
The aircraft
- Airframe total time: 7,379 hours
- Last inspection: approved inspection programme, March 26, 2012; 36 hours since
- Maximum gross weight: 5,250 lb
- Seats: 4
- Landing gear: fixed
- Engine: Rolls-Royce 250-C47B (turboshaft); 3,117 hours total
- Operator: Med-Trans CORP
The flight
- Departed from: KABR Aberdeen SD at 7:50 am
- Destination: SD54 Aberdeen SD
Weather at the time
- Light: night
- Wind: from 240° at 3 knots
- Visibility: 5 statute miles
- Sky: clear
- Temperature: 37°F (3°C), dew point 36°F (2°C)
- Altimeter: 29.70 inHg
- Observation at 7:53 am from KABR, 2 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight 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.
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.