# NTSB LAX85LA403: Hughes 369D, N29707, Porterville, CA, September 25, 1985

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Limited investigation · Final report
- Date: September 24, 1985, 18:00 local (Sep 25, 1985, 01:00 UTC)
- Place: Porterville, CA
- Coordinates: 35.960166, -118.920677 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=35.9602&lon=-118.9207&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 2 serious
- Status: Completed
- Report: Approved by Office Director
- NTSB case key (mKey): 24845
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX85LA403
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/24845/pdf
- Page: https://openairdocs.org/ntsb/LAX85LA403

## Sequence of events

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

- Loss of control - in flight, cruise - normal
  - rotorcraft flight control,tail rotor control - fatigue (cause)
  - airspeed(vmo) - exceeded, pilot in command (cause)
  - rotor drive system,tail rotor gearbox(90 deg) - separation (cause)
- In flight collision with terrain/water, landing - flare/touchdown
  - terrain condition - mountainous/hilly
  - directional control - not obtained, pilot in command (cause)

## Analysis

AFTER CLIMBING TO A CRUISE ALT OF 13500 FT MSL TO CROSS THE SIERRA NEVADA MOUNTAINS, SOUTH OF MT WHITNEY, THE PLT ENTERED CRUISE FLT AT AN INDICATED AIRSPEED OF APRX 120 TO 130 KTS. THE PLT'S FLT MANUAL LISTS 110 KTS AS THE VELOCITY VELOCITY TO NEVER EXCEED AT THIS PRESSURE ALT AND TEMP. THE PLT STATED THAT HE FIRST FELT A RAPID VIBRATION IN THE ANTI-TORGUE PEDALS. HE SAID HE THEN ENTERED A DESCENT. AS THE ACFT DESCENDED TO APRX 300 FT AGL IT WAS JOLTED AND DIRECTIONAL CONTROL WAS LOST. THE PLT STATED THAT HE MADE AN UNCONTROLLED FORCED LANDING AND CRASHED ON A MOUNTAIN AT AN ELEVATION OF 9000 FT. BOTH THE PLT AND HIS PASSENGER SURVIVED FOR 2 1/2 DAYS BEFORE BEING FOUND BY HUNTERS.

## Aircraft

- Registration: [N29707](https://openairdocs.org/deregistered/N29707-2013-06-06), registration cancelled 2013-06-06, S/N 670148D, built 1977 (OpenAirDocs)
- Reported make and model: HUGHES 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: 670148D
- Airframe hours: 1424
- Engines: ALLISON 250-C20B 420 horsepower turbo shaft
- Damage: Destroyed
- Flight: Personal, Part 91
- Operator: Michael G. Dawson, doing business as North Valley Helicopter
- Airworthiness certificate: Standard, Utility; Standard, Normal
- Last inspection: Annual, September 3, 1985, 7 hours before
- Departed: FAT, FRESNO, CA
- Destination: LAS, LAS VEGAS, NV

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 36; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 4,000 total

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 50 statute miles
- Lowest ceiling: none
- Temperature: 91 °F, dew point 41 °F
- Altimeter: 30.00 inHg
- Observed at: NID, 37 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 19850924075939A](https://openairdocs.org/incident/19850924075939A), Sep 24, 1985: Hughes 369D, Porterville, CA, Destroyed. Rapid vibration while exceeding recommended velocity. Descent, lost directional control. Fracture in pitch housing.

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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