# NTSB LAX91LA191: Hiller UH-12E, N4414, Delano, CA, May 4, 1991

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: May 3, 1991, 19:00 local (May 4, 1991, 02:00 UTC)
- Place: Delano, CA
- Coordinates: 35.780582, -119.230796 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=35.7806&lon=-119.2308&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report January 25, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 27187
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX91LA191
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/27187/pdf
- Page: https://openairdocs.org/ntsb/LAX91LA191

## Probable cause

THAT THE PILOT IMPROPERLY PERFORMED THE AUTOROTATION BY MISJUDGING THE FLARE ALTITUDE.  CONTRIBUTING TO THIS ACCIDENT WAS THE TOTAL FAILURE OF THE FREEWHEELING SPRAG CLUTCH DUE TO EXCESSIVE WEAR AND THE SOFT DIRT TERRAIN.

## 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,freewheeling sprag unit - failure,total (contributing factor)
  - rotor drive system,freewheeling sprag unit - worn (contributing factor)
- Forced landing, descent - emergency
  - autorotation - performed, pilot in command
- Hard landing, landing - flare/touchdown
  - flare - improper, pilot in command (cause)
  - altitude - misjudged, pilot in command (cause)
- Roll over, landing - flare/touchdown
  - terrain condition - soft (contributing factor)

## Analysis

SHORTLY AFTER LIFING OFF A PRIVATELY OWNED AIRSTRIP THE ENGINE EXPERIENCED AN OVERSPEED CONDITION.  THE PILOT EXECUTED AN AUTOROTATION INTO AN OPEN FIELD.  DURING THE AUTOROTATION THE PILOT MISJUDGED THE FLARE ALTITUDE, LANDED HARD CAUSING THE MAIN ROTOR BLADES TO SEVERE THE TAILBOOM ASSEMBLY. THE HELICOPTER ROLLED OVER ONTO ITS LEFT SIDE AS THE FORWARD LEFT SKID DUG INTO THE SOFT TERRAIN.

## Aircraft

- Registration: [N4414](https://openairdocs.org/deregistered/N4414-2014-12-17), registration cancelled 2014-12-17, S/N 2205, built 1962 (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 VO-540 series](https://openairdocs.org/engine/lycoming-vo-540-series) (registry code 41534, reciprocating) (OpenAirDocs)
- Category: Helicopter
- Serial number: 2205
- Airframe hours: 12556
- Engines: LYCOMING VO-540-C2A 305 horsepower reciprocating
- Damage: Substantial damage
- Flight: Aerial application, Part 137
- Operator: San Joaquin Helicopters Inc.
- Registered owner: San Joaquin Helicopters Inc
- Last inspection: Annual, April 11, 1991, 18 hours before

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 37; commercial; airplane ratings: single-engine land; medical: class 2, valid medical--w/ waivers/lim; flight hours: 1,000 total, 38 in this make and model, 960 as pilot in command, 58 in the last 90 days, 30 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Visibility: 15 statute miles
- Lowest ceiling: none

## 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 19910503014169A](https://openairdocs.org/incident/19910503014169A), May 3, 1991: Hiller UH12E, Delano, CA, Substantial damage. Engine went into overspeed on liftoff. Aborted,landed hard. Main rotors severed tailboom. Spraque clutch worn out.

## Other investigations on N4414 (2)

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 LAX80FVA03](https://openairdocs.org/ntsb/LAX80FVA03-201195), Oct 17, 1979: Hiller UH-12E (N4414), Mendota, CA, substantial damage
- [NTSB SEA69D0043](https://openairdocs.org/ntsb/SEA69D0043), Jul 27, 1968: Hiller UH-12E (N4414), Rockford, ID, 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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