# NTSB CHI89DEM09: Hiller UH-12E, N4028T, Hudsonville, MI, September 28, 1989

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Final report
- Date: September 28, 1989, 07:45 local (11:45 UTC)
- Place: Hudsonville, MI
- Coordinates: 42.860935, -85.859397 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=42.8609&lon=-85.8594&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor
- Status: Completed, report June 30, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 14201
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI89DEM09
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/14201/pdf
- Page: https://openairdocs.org/ntsb/CHI89DEM09

## Probable cause

THE FATIGUE FAILURE OF ONE OF THE TENSION-TORSION PINS.

## Sequence of events

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

- Airframe/component/system failure/malfunction, cruise
  - rotor system - fatigue (cause)
  - rotor system - failure,partial (cause)
- Forced landing, descent - emergency
  - autorotation - performed, pilot in command
- Loss of control - in flight, descent - emergency
  - misc rotorcraft,tail boom - separation
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

APPROXIMATELY 10 MINUTES AFTER TAKEOFF AT AN ALTITUDE OF 300 FT AGL AND AN AIRSPEED OF 60 KTS, THE PILOT EXPERIENCED A SEVERE VIBRATION AND A DECREASE IN RESPONSE TO CONTROL INPUTS. THE PILOT ENTERED AN AUTOROTATION AND WHEN APPROXIMATELY 10 - 15 FT AGL, THE TAIL BOOM WAS SEPARATED BY THE MAIN ROTOR. THE HELICOPTER THEN DESCENDED, NOSE FIRST, TO TERRAIN IMPACT. INSPECTION REVEALED A TENSION-TORSION PIN HAD FAILED AT THE DRAG BRACE BOLT HOLE. PRE-EXISTING CRACKS WERE FOUND EXTENDING FROM THE PIN SHANK TO THE BOLT HOLE.

## Aircraft

- Registration: [N4028T](https://openairdocs.org/deregistered/N4028T-1999-06-10), registration cancelled 1999-06-10, S/N 5097 (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: 5097
- Airframe hours: 1197
- Engines: LYCOMING VO-540-C2A 305 horsepower reciprocating
- Damage: Substantial damage
- Flight: Aerial application, Part 137
- Registered owner: Byron Ag Aviation, Inc.
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, February 18, 1989, 77 hours before
- Departed: NONE, BYRON CENTER, MI
- Destination: NONE, HUDSONVILLE, MI

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 42; airline transport, flight instructor; airplane ratings: single-engine land; instrument ratings: airplane, helicopter; medical: class 1, valid medical--no waivers/lim.; seat: center; flight hours: 8,900 total, 220 in this make and model, 8,800 as pilot in command, 120 in the last 90 days, 34 in the last 30 days, 1 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 210° at 7 knots
- Visibility: 15 statute miles
- Lowest ceiling: none
- Temperature: 46 °F, dew point 39 °F
- Altimeter: 30.00 inHg
- Observed at: GRR, 18 nm away

## 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 19890928036999A](https://openairdocs.org/incident/19890928036999A), Sep 28, 1989: Hiller UH12E, Hudsonville, MI, Substantial damage. Vibration on climbout, main rotor severed tailboom. Crashed nose down. Main rotor torsion pins broke. Prior cracks.

## Other investigations on N4028T (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 FTW98LA253](https://openairdocs.org/ntsb/FTW98LA253), Jun 2, 1998: Hiller UH-12E (N4028T), Delaplaine, AR, substantial damage. Probable cause: The failure of maintenance personnel to comply with and airworthiness directive, which resulted in failure of the planetary gear due to lack of lubrication. A contributing factors was the lack of…

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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