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 November 2, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 14, 2012 · about 7:55 am local time · cases in 2012
- 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 other cases naming the engine
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
6 documents, released by the NTSB on November 14, 2013. View them here, or download them; the NTSB redacts some personal details before release, and this site shows the NTSB's own titles rather than its file names.
| # | Document | What it is | |
|---|---|---|---|
| 1 | Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 | PDF, 9 pages | View Download |
| 2 | Witness Statement | PDF, 1 page | View Download |
| 3 | Photo 1: Wreckage Overview (Photo from Med-trans) | PDF, 1 page | View Download |
| 4 | Reports from Parties to the Investigation: Engine Examination Summary | PDF, 1 page | View Download |
| 5 | Statement of Party Representatives to NTSB Investigation | PDF, 2 pages | View Download |
| 6 | Release of Aircraft Wreckage, NTSB Form 6120.15 | PDF, 1 page | View Download |
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
Connections how this case links to the rest of the register
- N509MT on the register today · the tail number may have moved to another aircraft since
- Bell 407 984 registered today · the model family and its accident history
- Bell 3,080 aircraft on the register
- Engine: Rolls-Royce 250-C47B 536 aircraft carry this series today · as the NTSB recorded it
- Aberdeen Regional · departed from
- Avera St. Luke'S Heliport · bound for
- Accidents and incidents in South Dakota 469 since 1982 · 69 in the last ten years
- South Dakota 2,276 aircraft registered
The whole map of how records connect · these connections as data: /graph/accident/CEN12LA242.json.
The bigger picture in Aviation Analytics: accidents over time since 1982, by model, by phase of flight and conditions, by place and on the map.
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 does not name anyone involved, its policy at this time. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.