# NTSB CHI91LA097: Hughes 269C, N8955F, North Mankato, MN, February 20, 1991

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Limited investigation · Final report
- Date: February 20, 1991, 10:00 local (16:00 UTC)
- Place: North Mankato, MN
- Coordinates: 44.159736, -93.9897 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=44.1597&lon=-93.9897&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 2 serious, 1 minor
- Status: Completed, report October 8, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 15012
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI91LA097
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/15012/pdf
- Page: https://openairdocs.org/ntsb/CHI91LA097

## Probable cause

THE FATIQUE FAILURE OF THE TAIL BOOM SUPPORT STRUT ATTACHMENT CLUSTER AND THE IMPROPER INSPECTION OF THE CLUSTER ATTACHMENT.

## Sequence of events

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

- Airframe/component/system failure/malfunction, maneuvering
  - misc rotorcraft - fatigue (cause)
  - maintenance,inspection - inadequate (cause)
  - rotor drive system,tail rotor drive shaft - failure,total
- Loss of control - in flight, maneuvering
  - aircraft handling - not possible, pilot in command
- In flight collision with terrain/water, descent - uncontrolled
  - object - tree(s)

## Analysis

THE PILOT REPORTED THAT DURING THE AERIAL OBSERVATION FLIGHT HE HEARD A LOUD NOISE FROM THE BACK OF THE HELICOPTER. THE HELICOPTER THEN BEGAN ROTATING CLOCKWISE AND DESCENDED TO IMPACT WITH THE TERRAIN IN A WOODED AREA.  POST ACCIDENT IMSPECTION REVEALED A FATIGUE FAILURE OF THE TAIL BOOM SUPPORT STRUT CLUSTER FITTING (LEFT SIDE).  AN AIRWORTHINESS DIRECTIVE ISSUED IN 1976 CALLED FOR A DAILY VISUAL INSPECTION AND A 200 HOUR DYE PENETRANT INSPECTION OF THE FITTING. A LOGBOOK ENTRY DATE AUGUST 15, 1990, STATED ALL AD'S HAD BEEN COMPLIED WITH.

## Aircraft

- Registration: [N8955F](https://openairdocs.org/deregistered/N8955F-1995-01-30), registration cancelled 1995-01-30, S/N 1120172 (OpenAirDocs)
- Reported make and model: HUGHES 269C
- Registry model: [Hughes 269C](https://openairdocs.org/model/hughes-269c) (registry code 4470504) (OpenAirDocs)
- Category: Helicopter
- Serial number: 1120172
- Engines: LYCOMING HIO-360-D1A 190 horsepower reciprocating
- Damage: Destroyed
- Flight: Business, Part 91
- Operator: Helicopter Flight, Inc.
- Departed: MKT, MANKATO, MN

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 41; commercial; medical: class 2, valid medical--no waivers/lim.; flight hours: 2,244 total, 38 in this make and model, 2,207 as pilot in command, 58 in the last 90 days, 34 in the last 30 days, 8 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 210° at 6 knots
- Visibility: 15 statute miles
- Lowest ceiling: 10,000 ft overcast
- Temperature: -0 °F, dew point -0 °F

## 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 19910220002889A](https://openairdocs.org/incident/19910220002889A), Feb 20, 1991: Hughes 269C, North Mankato, MN, Destroyed. Lost tail rotor control. Descended into trees. Tailboom cluster fittings fatigue failed. Shifted boom broke shaft.

## Other investigations on N8955F (1)

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.

- [NTSB SEA74DYE17](https://openairdocs.org/ntsb/SEA74DYE17), Sep 16, 1973: Hughes 269C (N8955F), Eagle Lake, WA, substantial damage

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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