# NTSB LAX90LA029: Bell-Kitz Kopters 47D1, N6324X, Chino, CA, November 10, 1989

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: November 10, 1989, 14:39 local (22:39 UTC)
- Place: Chino, CA
- Coordinates: 33.999855, -117.679786 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=33.9999&lon=-117.6798&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report January 23, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 26682
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX90LA029
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/26682/pdf
- Page: https://openairdocs.org/ntsb/LAX90LA029

## Probable cause

A FATIGUE FAILURE OF BOTH THE MAIN ROTOR STABILIZER BAR TUBE AND THE TIE ROD. IN ADDITION, THE TIE ROD NUT WAS LOOSE AND DID NOT CONFORM TO ENGINEERING DRAWING SPECIFICATIONS. COMPANY PERSONNEL FAILED TO DETECT THE FATIGUE CRACKS DURING DAILY INSPECTIONS.

## Sequence of events

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

- Airframe/component/system failure/malfunction, approach - vfr pattern - downwind
  - rotor system,stabilizer bar - failure,total (cause)
  - rotor system,stabilizer bar - bent (cause)
  - rotor system,stabilizer bar - fatigue (cause)
  - rotor system - unapproved part (cause)
  - maintenance,inspection - inadequate, company maintenance personnel (cause)
  - maintenance,installation - intentional, company maintenance personnel (cause)
- Forced landing, landing - flare/touchdown
  - autorotation - performed, pilot in command
- Roll over, landing - flare/touchdown
  - terrain condition - soft (contributing factor)

## Analysis

THE STUDENT PILOT WAS PRACTICING TOUCH AND GO TAKEOFFS AND LANDINGS. WHILE ON THE DOWNWIND LEG THE STUDENT PILOT RPTD THAT THE HELICOPTER BEGAN TO VIBRATE AND THEN VIOLENTLY PITCHED UP. THE STUDENT PILOT IMMEDIATELY EXECUTED AN AUTOROTATION INTO A COW PASTURE. THE WRECKAGE EXAM DSCLSD THE MAIN ROTOR STABILIZER BAR SEPARATED IN FLT AND IT WAS NOT FOUND. THE ATTACH SECTION OF THE BAR REMAINED CONNECTED AT ITS ATTACH POINTS. METALLURGICAL EXAM DSCLSD THE INNER BAR AND THE TIE ROD FRACTURED IN FATIGUE WHICH HAD PROPAGATED VERY SLOWLY, AND CRACKS WOULD HAVE BEEN EVIDENT. BELL HELICOPTER HAD ISSUED SERVICE BULLETIN 47-(04-2)73-1 REQUIRING DAILY INSPECTION OF THE BAR FOR CRACKS. THE TIE ROD NUT WAS A BOGUS PART AND EXCESSIVELY WORN.

## Aircraft

- Registration: N6324X (not matched to a registry record)
- Reported make and model: Bell-Kitz Kopters 47D1
- Category: Helicopter
- Serial number: T-610
- Engines: FRANKLIN 6V4 200 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: Petkow, Raymond, doing business as Meadowlark Aviation
- Registered owner: Raymond Petkow
- Airworthiness certificate: Standard, Normal
- Departed: CNO
- Destination: CNO
- Airport: CNO, Chino

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 28; student; medical: class 3, valid medical--no waivers/lim.; seat: left; flight hours: 40 total, 40 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 30 statute miles
- Lowest ceiling: none
- 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 19891110044899A](https://openairdocs.org/incident/19891110044899A), Nov 10, 1989: Bell 47D1, Chino, CA, Substantial damage. Vibration and pitch-up. Autorotated but touched nose down in berm,nosed over. Stabilizer bar failed. Bogus rod nuts

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.