# NTSB LAX88LA179: McDonnell Douglas 369D, N4943T, Waialua, HI, May 13, 1988

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Limited investigation · Final report
- Date: May 13, 1988, 10:15 local (20:15 UTC)
- Place: Waialua, HI
- Coordinates: 21.570901, -158.12059 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=21.5709&lon=-158.1206&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 1 serious
- Status: Completed, report July 9, 1990
- Report: Approved by Office Director
- NTSB case key (mKey): 25999
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX88LA179
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/25999/pdf
- Page: https://openairdocs.org/ntsb/LAX88LA179

## Probable cause

FAILURE TO FOLLOW PROCEDURES ESTABLISHED BY THE MANUFACTURE FOR UNCOMMANDED TRIM INPUTS AND HIS DECISION TO MAKE A HOVER APPROACH TO LANDING.

## Sequence of events

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

- Loss of control - in flight, hover
  - rotorcraft flight control system,collective trim - shorted (contributing factor)
  - trim setting - uncontrolled, pilot in command (contributing factor)
  - procedures/directives - not followed, pilot in command (cause)
  - in-flight planning/decision - improper, pilot in command (cause)
- In flight collision with terrain/water, descent - uncontrolled
  - terrain condition - ditch

## Analysis

THE HELICOPTER WAS RETURNING TO ITS LONG LINE PICKUP POINT FOR ANOTHER LOAD WHEN IT ENTERED AN UNCOMMANDED LEFT ROLL. THE PILOT REGAINED CONTROL OF THE HELICOPTER, RELEASED THE LONG LINE CABLE AND ENTERED A SHALLOW, SLOW APPROACH TO A HOVER IN A VACANT AREA. AS THE SKIDS NEARED THE GROUND THE HELICOPTER ROLLED LEFT TO AN ANGLE OF 45 DEGREES, BEGAN TO CLIMB, THEN CRASHED INTO AN IRRIGATION DITCH. THE EXAMINATION REVEALED METAL PARTICLES CONTAMINATING THE TRIM ACTUATOR SWITCH. ACCORDING TO THE MANUFACTURER, THE HELICOPTER IS CONTROLLABLE WITH A MALFUNCTIONING TRIM SYSTEM; HOWEVER, THE CIRCUIT BRAKERS SHOULD BE PULLED. THE PILOT STATED HE RESET THE CIRCUIT BREAKERS.

## Aircraft

- Registration: [N4943T](https://openairdocs.org/deregistered/N4943T-2013-07-10), registration cancelled 2013-07-10, S/N 1190614D, built 1979 (OpenAirDocs)
- Reported make and model: McDonnell Douglas 369D
- Registry model: [Hughes Helicopters HUGHES 369D](https://openairdocs.org/model/hughes-helicopters-hughes-369d) (registry code 4470706) (OpenAirDocs)
- Registry engine: [Allison 250-C20 series](https://openairdocs.org/engine/allison-250-c20-series) (registry code 03020, turbo-prop) (OpenAirDocs)
- Category: Helicopter
- Serial number: 400694D
- Airframe hours: 3102
- Engines: ALLISON 250-C20B 420 horsepower turbo shaft
- Damage: Destroyed
- Flight: Part 133
- Operator: Cherry Helicopters, Inc.
- Registered owner: Cherry Helicopters Inc
- Airworthiness certificate: Standard, Normal; Standard, Utility
- Last inspection: 100 hour, April 10, 1988, 82 hours before
- Departed: WAIALUA, HI
- Airport: Field

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 41; airline transport, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane, helicopter; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 8,600 total, 5,000 in this make and model, 8,600 as pilot in command, 250 in the last 90 days, 80 in the last 30 days, 1 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 20° at 3 knots, gusting 7
- Visibility: 7 statute miles
- Lowest ceiling: 2,000 ft broken
- Temperature: 75 °F, dew point 66 °F
- Altimeter: 30.00 inHg
- Observed at: HHI

## 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 19880513046499A](https://openairdocs.org/incident/19880513046499A), May 13, 1988: Hughes 369D, Waialua, HI, Destroyed. Began uncommanded turn while hovering to land. Reported cyclic hardover. Possible malfunctioned cyclic trim switch.

## Other investigations on N4943T (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 LAX94LA241](https://openairdocs.org/ntsb/LAX94LA241), Jun 7, 1994: Hughes 369D (N4943T), Kaneohe, HI, substantial damage. Probable cause: the operator's and pilot's failure to ensure that the cargo net containing empty paper bags was sufficiently ballasted to prevent it from flying up into the tail rotor.

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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