Mbb BK-117A-1 accident near Janesville, Wisconsin, January 30, 1990
On January 30, 1990 at about 7:10 pm local time, a Mbb BK-117A-1 (helicopter), registered N117M, was substantially damaged in an accident near Janesville, Wisconsin. It was a flight of an unrecorded kind under general aviation rules (Part 91). No one was hurt; 2 people were on board or involved. The weather was visual conditions (good weather).
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The NTSB's probable cause their words, unchanged
THE PILOT-IN-COMMAND FAILED TO ENSURE THAT THE ENGINE COWLING LATCHES WERE PROPERLY SECURED PRIOR TO DEPARTING ON THE MAINTENANCE TEST FLIGHT; THE COWLING CAME LOOSE DURING FLIGHT, AND CONTACTED THE MAIN ROTOR BLADES BEFORE IT SEPARATED FROM THE HELICOPTER.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- January 30, 1990 · about 7:10 pm local time
- Place
- Janesville, Wisconsin · map
- Type
- Accident
- Injuries
- No one was hurt; 2 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Mbb BK-117A-1
- Registration
- N117M · registry record · serial S-7023
- Damage
- Substantial damage
- Flight
- Flight of an unrecorded kind · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
THE PILOT STATED THAT HE AND A COMPANY MECHANIC WERE IN CRUISE FLIGHT AT 2,000 FEET MSL ON A MAINTENANCE FLIGHT TEST, WHEN HE HEARD A NOISE, 'OBSERVED DEBRIS IN ALL DIRECTIONS FROM THE MAIN ROTOR...(AND) SEVERE VIBRATION WAS EXPERIENCED.' THE PILOT MADE AN EMERGENCY LANDING IN A SNOW-COVERED FIELD. POST-ACCIDENT EXAMINATION REVEALED THAT THE ENGINE COWLING ON THE LEFT SIDE OF THE AIRCRAFT HAD SEPARATED WHILE IN FLIGHT, CONTACTING AND DAMAGING THE MAIN ROTOR BLADES. SEVERAL PIECES OF THE SEPERATED COWLING WERE RECOVERED AND INSPECTED. THE LATCHES SHOWED NO MALFORMATION/STRETCHING, AND APPEARED TO BE CAPABLE OF NORMAL OPERATION.
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: 5,869 hours in all; 62 in this make and model; 78 in the last 90 days; 16 in the last 30 days; 5,799 as pilot in command
- Medical certificate: Class 2 (valid medical--no waivers/lim.)
- Seat: rgt
The aircraft
- Airframe total time: 3,397 hours
- Last inspection: approved inspection programme, January 12, 1990; 10 hours since
- Maximum gross weight: 7,056 lb
- Seats: 8
- Landing gear: fixed
- Engine: Lycoming LTS-101-650B1 (turboshaft); 0 hours total
- Operator: Omni Flight Helicopters, INC.
The flight
- Departed from: JVL Janesville WI at 7:00 pm
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 280° at 18 knots, gusting 25
- Visibility: 15 statute miles
- Sky: clear
- Temperature: 41°F (5°C), dew point 0°F (-18°C)
- Altimeter: 29.00 inHg
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | |||
| Passengers | 1 |
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The docket at the NTSB holds the report as a PDF and the investigation's photographs and documents. This site never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number CHI90LA074.