# NTSB LAX94LA235: Bell 47D-1, N14412, Chino, CA, June 2, 1994

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: June 2, 1994, 12:46 local (19:46 UTC)
- Place: Chino, CA
- Coordinates: 34.000858, -117.68077 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=34.0009&lon=-117.6808&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report November 14, 1994
- Report: Approved by Office Director
- NTSB case key (mKey): 28756
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX94LA235
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/28756/pdf
- Page: https://openairdocs.org/ntsb/LAX94LA235

## Probable cause

loss of aircraft control due to the pilot's failure to correctly configure the hydraulic system prior to takeoff.

## Sequence of events

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

- Loss of control - in flight, hover
  - hydraulic system - not engaged (cause)
  - aircraft preflight - inaccurate, pilot in command (cause)
  - aircraft control - not maintained, pilot in command (cause)
- Roll over, hover

## Analysis

The pilot reported that she lifted into a hover in preparation for takeoff and the helicopter began a pilot inducted oscillation due to heavy cyclic control forces. The pilot stated that she overcompensated on the controls and the helicopter rolled over.  The pilot reported that during the run-up procedure she disengaged the hydraulic system to check the rotor tip path plane and forgot to reengage the system prior to lifting into a hover. The pilot said there was no mechanical malfunction or failure of any system.

## Factual narrative

On June 2, 1994, at 1246 Pacific daylight time, a Bell 47D-1 helicopter, N14412, rolled over during hover at the Chino, California, airport.  The aircraft was in a hover in preparation for takeoff from a helipad on the airport.  The helicopter was owned and operated by Mike Zemlock Helicopters of Chino and was rented by the pilot for a local area personal flight.  Visual meteorological conditions prevailed at the time and no flight plan was filed for the operation.  The aircraft incurred substantial damage.  The certificated private pilot, the sole occupant, was not injured.  The flight was originating at the time of the occurrence.

In a telephone interview, the pilot reported that she lifted into a hover in preparation for takeoff and the helicopter began a pilot inducted oscillation due to heavy cyclic control forces.  The pilot stated that she overcompensated on the controls and the helicopter rolled over.  The pilot reported that during the run-up procedure she disengaged the hydraulic system to check the rotor tip path plane and forgot to reengage the system prior to lifting into a hover.  The pilot said there was no mechanical malfunction or failure of any system.

## Aircraft

- Registration: [N14412](https://openairdocs.org/deregistered/N14412-2001-08-02), registration cancelled 2001-08-02, S/N 996 (OpenAirDocs)
- Reported make and model: BELL 47D-1
- Registry model: [Bell 47D1](https://openairdocs.org/model/bell-47d1) (registry code 1180802) (OpenAirDocs)
- Category: Helicopter
- Serial number: 996
- Airframe hours: 7661
- Engines: FRANKLIN 6V4-200-C32 200 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: Zemlock, Mike, doing business as Zemlock Helicopter Service
- Registered owner: Zemlock, Mike
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, May 6, 1994, 61 hours before
- Airport: CNO, Chino

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 47; private; airplane ratings: single-engine land; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 1,619 total, 216 in this make and model, 1,428 as pilot in command

## Weather

- Conditions: Visual (VMC), Day
- Wind: 240° at 5 knots
- Visibility: 6 statute miles
- Temperature: 81 °F
- Altimeter: 29.00 inHg
- Observed at: CNO

## 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 19940602013379A](https://openairdocs.org/incident/19940602013379A), Jun 2, 1994: Bell 47D1, Chino, CA, Substantial damage. Lifted off pad to hover. Began pilot induced oscillation due heavy cylic force. Forgot to engage hydraulic system.

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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