# NTSB CHI90LA074: MBB BK-117A-1, N117M, Janesville, WI, January 30, 1990

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: January 30, 1990, 13:10 local (19:10 UTC)
- Place: Janesville, WI
- Coordinates: 42.679656, -89.009078 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=42.6797&lon=-89.0091&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report December 30, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 14626
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI90LA074
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/14626/pdf
- Page: https://openairdocs.org/ntsb/CHI90LA074

## Probable cause

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.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, cruise
  - engine compartment - not secured (cause)
  - aircraft preflight - inadequate, pilot in command (cause)
  - nacelle/pylon,fairing - separation (cause)
  - rotor system,main rotor blade - failure,partial
- Forced landing, descent - emergency
  - terrain condition - open field
  - run on landing - performed, pilot in command
  - terrain condition - snow covered

## Analysis

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.

## Aircraft

- Registration: [N117M](https://openairdocs.org/deregistered/N117M-2013-02-22), registration cancelled 2013-02-22, S/N 7023 (OpenAirDocs)
- Reported make and model: MBB BK-117A-1
- Registry model: [MBB BK 117 A-3](https://openairdocs.org/model/mbb-bk-117-a-3) (registry code 5626015) (OpenAirDocs)
- Category: Helicopter
- Serial number: S-7023
- Airframe hours: 3397
- Engines: LYCOMING LTS-101-650B1 600 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Part 91
- Operator: Omni Flight Helicopters, Inc.
- Registered owner: First Security Bank Of Utah
- Airworthiness certificate: Standard, Normal
- Last inspection: AAIP, January 12, 1990, 10 hours before
- Departed: JVL, JANESVILLE, WI

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 36; commercial; airplane ratings: single-engine land; medical: class 2, valid medical--no waivers/lim.; seat: right; flight hours: 5,869 total, 62 in this make and model, 5,799 as pilot in command, 78 in the last 90 days, 16 in the last 30 days, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 280° at 18 knots, gusting 25
- Visibility: 15 statute miles
- Lowest ceiling: none
- Temperature: 41 °F
- Altimeter: 29.00 inHg

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19900130001369A](https://openairdocs.org/incident/19900130001369A), Jan 30, 1990: Bolkms BK117A1, Janesville, WI, Substantial damage. Engine cowling came loose on test flight. Emergency landing due to damaged rotors.

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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