# NTSB CHI89DEP04: Hiller UH-12E, N3829, Waterford, WI, May 22, 1989

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Final report
- Date: May 22, 1989, 09:00 local (14:00 UTC)
- Place: Waterford, WI
- Coordinates: 42.759864, -88.209365 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=42.7599&lon=-88.2094&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report August 2, 1990
- Report: Approved by Office Director
- NTSB case key (mKey): 14206
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI89DEP04
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/14206/pdf
- Page: https://openairdocs.org/ntsb/CHI89DEP04

## Probable cause

THE PILOT'S INABILITY TO MAINTAIN CONTROL DURING AN AUTOROTATIONAL LANDING ATTEMPT FOLLOWING THE FAILURE OF THE MAIN ROTOR DRIVE TRAIN TORSIONAL COUPLING.

## Sequence of events

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

- Airframe/component/system failure/malfunction, cruise - normal
  - rotor drive system - failure,total (cause)
- Forced landing, descent - emergency
- Loss of control - in flight, descent - emergency
  - autorotation - not possible (cause)
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

WHILE IN NORMAL CRUISE FLIGHT THE HELICOPTER EXPERIENCED A VIBRATION. THE PILOT ELECTED TO MAKE A PRECAUTIONARY LANDING AND DURING ATTEMPTED AUTOROTATION CONTROL WAS LOST. THE INVESTIGATION REVEALED THE MAIN ROTOR DRIVE TRAIN TORSIONAL COUPLING HAD FAILED.

## Aircraft

- Registration: [N3829](https://openairdocs.org/aircraft/N3829), registered now, S/N 1425 (OpenAirDocs)
- Reported make and model: HILLER UH-12E
- Registry model: [Hiller UH-12E](https://openairdocs.org/model/hiller-uh-12e) (registry code 4360122) (OpenAirDocs)
- Category: Helicopter
- Serial number: 1425
- Airframe hours: 5851
- Engines: LYCOMING VO-540-C2A 305 horsepower reciprocating
- Damage: Substantial damage
- Flight: Positioning, Part 91
- Operator: A.I.R. Helicopter Service, Inc
- Registered owner: Jon Mar Leasing Corp.
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: Annual, May 1, 1988, 64 hours before
- Departed: WATERFORD, WI

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 58; commercial; airplane ratings: single-engine land; medical: class 2, valid medical--no waivers/lim.; seat: center; flight hours: 4,200 total, 800 in this make and model, 4,200 as pilot in command, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 70 °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 19890522012119A](https://openairdocs.org/incident/19890522012119A), May 22, 1989: Hiller UH12E, Waterford, WI, Substantial damage. Main rotor torsion coupling failed. Helicopter became uncontrollable and impacted vertically.

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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