# NTSB DEN88LA046: Hiller UH-12E, N400AH, Vernal, UT, January 2, 1988

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: January 2, 1988, 15:30 local (22:30 UTC)
- Place: Vernal, UT
- Coordinates: 40.549015, -109.570037 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=40.5490&lon=-109.5700&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 3 uninjured
- Status: Completed, report March 30, 1989
- Report: Approved by Office Director
- NTSB case key (mKey): 17432
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN88LA046
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/17432/pdf
- Page: https://openairdocs.org/ntsb/DEN88LA046

## Sequence of events

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

- Loss of engine power(total) - mech failure/malf, cruise - normal
  - engine assembly,connecting rod - fatigue (cause)
  - maintenance,rebuild/remanufacture - poor, other maintenance personnel (cause)
  - engine assembly,connecting rod bolt - stripped thread (cause)
  - engine assembly,connecting rod cap - failure,total (cause)
- Forced landing, descent - emergency
  - autorotation - initiated
- Hard landing, landing - flare/touchdown
  - altitude - misjudged, pilot in command (cause)
  - flare - improper, pilot in command (cause)
  - misc rotorcraft,tail boom - sheared

## Analysis

THE COMMERCIAL PLT AND TWO PASSENGERS WERE SURVEYING A ROAD ROUTE IN MOUNTAINOUS TERRAIN. AT CRUISE, THE PILOT NOTICED A DROP IN MANIFOLD PRESSURE, FOLLOWED BY A LOSS OF OIL PRESSURE. THE PLT REPORTED THAT THE ENGINE QUIT. AN AUTOROTATION TO A SNOW COVERED ROAD RESULTED IN A HARD LANDING. THE MAIN ROTOR BLADES SEVERED THE TAIL BOOM AND THE LANDING SKIDS COLLAPSED. A POST ACCIDENT ENGINE TEAR DOWN REVEALED EVIDENCE CONSISTENT WITH CONNECTING ROD FAILURE. THE NUMBER FIVE ROD BEARING HAD DISINTEGRATED AND THE ROD END CAP HAD BROKEN IN SERVICE. THE DAMAGED ROD END CAP AND CONNECTING ROD WERE EXAMINED FOR FAILURE MODE DETERMINATION. THE METALLURGIST'S FACTUAL REPORT STATES THAT THE ROD SHOWS FRACTURE DETAILS CHARACTERISTICS OF HIGH CYCLE FATIGUE.

## Aircraft

- Registration: [N400AH](https://openairdocs.org/deregistered/N400AH-2003-04-22), registration cancelled 2003-04-22, S/N 1177, built 1975 (OpenAirDocs)
- Reported make and model: HILLER UH-12E
- Registry model: [Hiller UH-12E](https://openairdocs.org/model/hiller-uh-12e) (registry code 4360122) (OpenAirDocs)
- Registry engine: [Lycoming TI0-540 series](https://openairdocs.org/engine/lycoming-ti0-540-series) (registry code 41533, turbo-prop) (OpenAirDocs)
- Category: Helicopter
- Serial number: 1177
- Airframe hours: 6732
- Engines: LYCOMING TIVO-540-A2A 315 horsepower reciprocating
- Damage: Substantial damage
- Flight: Business, Part 91
- Registered owner: Ben J. Richards
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, August 29, 1987, 9 hours before
- Departed: VEL, VERNAL, UT

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 35; commercial; airplane ratings: single-engine land; medical: class 2, valid medical--no waivers/lim.; seat: center; flight hours: 5,450 total, 5,100 in this make and model, 5,100 as pilot in command, 30 in the last 30 days, 1 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 50 statute miles
- Lowest ceiling: none
- Temperature: 5 °F
- Observed at: RKS

## 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 19880102000119A](https://openairdocs.org/incident/19880102000119A), Jan 2, 1988: Hiller UH12E, Vernal, UT, Substantial damage. Engine quit en route. Made hard autorotation landing on a road. Connecting rod broken from engine overtemp operation

## Other investigations on N400AH (4)

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 DEN86LA016](https://openairdocs.org/ntsb/DEN86LA016), Nov 1, 1985: Hiller UH-12E (N400AH), Vernal, UT, substantial damage
- [NTSB DEN83LA204](https://openairdocs.org/ntsb/DEN83LA204), Aug 31, 1983: Hiller UH-12E (N400AH), Manning, ND, substantial damage
- [NTSB DEN81DTE08](https://openairdocs.org/ntsb/DEN81DTE08), Nov 17, 1981: Hiller UH12E (N400AH), Craig, CO, substantial damage
- [NTSB DEN79FTE64](https://openairdocs.org/ntsb/DEN79FTE64), Jul 24, 1979: Hiller 12E (N400AH), Longmont, CO, 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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