# NTSB SEA89LA177: Bell 47G, N47VS, Corvallis, OR, September 25, 1989

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: September 25, 1989, 10:10 local (17:10 UTC)
- Place: Corvallis, OR
- Coordinates: 44.630947, -123.270072 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=44.6309&lon=-123.2701&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor, 1 uninjured
- Status: Completed, report June 22, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 41084
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA89LA177
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/41084/pdf
- Page: https://openairdocs.org/ntsb/SEA89LA177

## Probable cause

STUDENT PILOT'S IMPROPER USE OF THE COLLECTIVE CONTROL WHILE PERFORMING HOVERING AUTOROTATIONS, AND THE INSTRUCTOR'S INADEQUATE SUPERVISION OF THE STUDENT'S ACTIONS, WHICH RESULED IN HARD LANDINGS. IN ADDITION, THE ENGINE MOUNT WAS SIGNIFICANTLY WEAKENED STRUCTUALLY AS A RESULT OF CORROSION.

## Sequence of events

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

- Hard landing, hover
  - autorotation - performed, dual student
  - collective - improper use of, dual student (cause)
  - supervision - inadequate, pilot in command(cfi) (cause)
- Loss of control - in flight, hover
  - engine assembly,mount - corroded (cause)
  - engine assembly,mount - fractured (cause)
  - engine assembly,mount - previous damage (cause)
- Roll over, hover

## Analysis

WHILE PRACTICING HOVERING AUTOROTATIONS ON AN ASPHALT TAXIWAY SEVERAL HARD LANDINGS OCCURRED AS A RESULT OF THE STUDENT'S DIFFICULTY LEARNING THE PROPER APPLICATION OF COLLECTIVE PITCH. THE CFI THEN INSTRUCTED THE STUDENT TO MOVE TO A SOD AREA ADJACENT TO THE TAXIWAY FOR THE CUSHIONING EFFECT TO REDUCE IMPACT FORCES ON THE AIRCRAFT. THE CFI SAID HE DID NOT INSPECT THE AIRCRAFT FOR DAMAGE AFTER THE HARD LANDINGS ON THE TAXIWAY. THE STUDENT THEN PERFORMED ONE HOVERING AUTOROTATION ON THE SOD AREA, AND DURING THE SUBSEQUENT HOVER CONTROL WAS LOST. THE AIRCRAFT ROLLED OVER AND IMPACTED THE GROUND. HEAVY SKID IMPACT MARKS WERE FOUND ON THE TAXIWAY. THE ENGINE MOUNT TUBULAR STRUCTURE AT THE BOTTOM MOUNT, AND THE CROSS MEMBER SUPPORT TUBES, WERE FRACTURED. THE WALLS OF THE TUBES WERE OF IRREGULAR THICKNESS, CONTAINED EXTENSIVE CORROSION SCALING, AND IN SOME PLACES COULD BE BENT BY HAND. THE BOTTOM OF THE ENGINE, WHICH IS MOUNTED TO THE TRANSMISSION AND MAIN ROTOR MAST, WAS FREE TO MOVE. LAST ANNUAL INSP. FIVE DAYS BEFORE ACCIDENT.

## Aircraft

- Registration: [N47VS](https://openairdocs.org/deregistered/N47VS-1990-07-20), registration cancelled 1990-07-20, S/N 1394 (OpenAirDocs)
- Reported make and model: BELL 47G
- Registry model: [Bell 47G](https://openairdocs.org/model/bell-47g) (registry code 1181002) (OpenAirDocs)
- Category: Helicopter
- Serial number: 1394
- Airframe hours: 8148
- Engines: FRANKLIN 6V335-B 200 horsepower reciprocating
- Damage: Destroyed
- Fire: On-Ground
- Flight: Instructional, Part 91
- Registered owner: Ali A. Brown
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, September 20, 1989, 1 hours before
- Departed: CVO, CORVALLIS, OR
- Airport: CVD, Corvallis

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 33; commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: right; flight hours: 1,294 total, 105 in this make and model, 1,043 as pilot in command, 16 in the last 90 days, 11 in the last 30 days, 1 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 10 statute miles
- Lowest ceiling: 4,000 ft overcast
- Temperature: 70 °F, dew point 55 °F
- Altimeter: 29.00 inHg
- Observed at: CVO

## 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 19890925036039A](https://openairdocs.org/incident/19890925036039A), Sep 25, 1989: Bell 47G, Corvallis, OR, Destroyed. Allowed student to hit runway several times during hover. Helicopter rolled over corroded motor mount fractured.

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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