# NTSB LAX86LA283: Texas Helicopter OH-13H/M, N51856, Valencia, CA, July 6, 1986

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Limited investigation · Final report
- Date: July 6, 1986, 08:20 local (15:20 UTC)
- Place: Valencia, CA
- Coordinates: 34.409622, -118.558998 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=34.4096&lon=-118.5590&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 1 serious
- Status: Completed
- Report: Approved by Office Director
- NTSB case key (mKey): 25206
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX86LA283
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/25206/pdf
- Page: https://openairdocs.org/ntsb/LAX86LA283

## Sequence of events

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

- Airframe/component/system failure/malfunction, maneuvering - aerial application
  - rotor drive system,main gearbox/transmission - failure,total (cause)
  - rotor drive system,main gearbox/transmission - overload (cause)
- Forced landing, descent - emergency
- In flight collision with terrain/water, landing - flare/touchdown

## Analysis

THE PILOT REPORTED THAT HE HEARD A LOUD BANG AND GRINDING NOISE FROM THE ENGINE/MAIN TRANSMISSION AREA WHILE ON A SWATH RUN. HE STATED THAT THE MAIN ROTOR RPM DECAYED IMMEDIATELY AFTER HE HEARD THE NOISE. AS THE HELICOPTER DESCENDED TO ABOUT 50 FEET ABOVE THE GROUND THE PILOT SAID HE FLARED FOR THE TOUCHDOWN. THE HELICOPTER LANDED HARD SEVERING THE SKIDS, TAIL AND SPRAY BOOMS. THE PILOT SAID THE ENGINE CONTINUED TO RUN AFTER THE ACCIDENT, HOWEVER, THE ROTOR WAS NOT TURNING. POST ACCIDENT INSPECTION OF THE TRANSMISSION REVEALED A MASSIVE OVERLOAD FAILURE OF THE LOWER PINION GEAR ASSEMBLY. BOGUS PINION GEARS WERE FOUND INSTALLED IN THE TRANSMISSION.

## Aircraft

- Registration: [N51856](https://openairdocs.org/deregistered/N51856-2022-02-08), registration cancelled 2022-02-08, S/N 78-023, built 1978 (OpenAirDocs)
- Reported make and model: TEXAS HELICOPTER OH-13H/M
- Registry model: [Texas Helicopter OH-13H/M74A](https://openairdocs.org/model/texas-helicopter-oh-13h-m74a) (registry code 8930105) (OpenAirDocs)
- Registry engine: [Lycoming VO-435-A1F](https://openairdocs.org/engine/lycoming-vo-435-a1f) (registry code 42200, reciprocating) (OpenAirDocs)
- Category: Helicopter
- Serial number: 78-023
- Airframe hours: 2743
- Engines: LYCOMING VO-435A/F 260 horsepower reciprocating
- Damage: Substantial damage
- Flight: Aerial application, Part 137
- Registered owner: Roy G. Cox
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: 100 hour, June 2, 1986, 47 hours before
- Departed: VALENCIA, CA
- Airport: VNY, Van Nuys

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 39; commercial; medical: class 2, valid medical--no waivers/lim.; seat: center; flight hours: 8,850 total, 1,500 in this make and model, 7,858 as pilot in command, 120 in the last 90 days, 40 in the last 30 days, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 7 statute miles
- Lowest ceiling: 2,000 ft overcast
- Temperature: 61 °F, dew point 61 °F
- Altimeter: 30.00 inHg
- Observed at: VNY, 10 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 19860706034439A](https://openairdocs.org/incident/19860706034439A), Jul 6, 1986: Bell OH13HTEXHELI, Van Nuys, CA, Substantial damage. Loud bang on spray run. Impacted field high sink rate. Main rotor pinion gear failed. Bogus in transmission.

## Other investigations on N51856 (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 LAX81DUQ26](https://openairdocs.org/ntsb/LAX81DUQ26), Jul 3, 1981: Texas Hel M74A (N51856), Rosamond, CA, 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.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.