# NTSB LAX91LA097: Robinson R22A, N8491A, Piru, CA, February 10, 1991

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: February 10, 1991, 15:20 local (23:20 UTC)
- Place: Piru, CA
- Coordinates: 34.430744, -118.749679 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=34.4307&lon=-118.7497&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report March 31, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 27112
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX91LA097
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/27112/pdf
- Page: https://openairdocs.org/ntsb/LAX91LA097

## Probable cause

FAILURE OF THE CFI TO MAINTAIN MAIN ROTOR RPM DURING A DEMONSTRATED AUTOROTATION.

## Sequence of events

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

- In flight collision with terrain/water, maneuvering
  - autorotation - intentional, pilot in command(cfi)
  - rotor rpm - not maintained, pilot in command(cfi) (cause)
- Roll over, landing - flare/touchdown

## Analysis

THE CFI WAS DEMONSTRATING A 180 DEGREE AUTOROTATION TO HIS STUDENT IN A 25 KT WIND. THE CFI ALLOWED THE MAIN ROTOR RPM TO BLEED OFF AND WAS UNABLE TO RECOVER THE RPM BEFORE TOUCHDOWN. THE HELICOPTER LANDED HARD AND THE MAIN ROTOR SEVERED THE TAILBOOM. THE HELICOPTER THEN ROLLED OVER.

## Aircraft

- Registration: [N8491A](https://openairdocs.org/aircraft/N8491A), registered now, S/N 0404, built 1984 (OpenAirDocs)
- Reported make and model: ROBINSON R22A
- Registry model: [Robinson Helicopter R22 ALPHA](https://openairdocs.org/model/robinson-helicopter-r22-alpha) (registry code 7640104) (OpenAirDocs)
- Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs)
- Category: Helicopter
- Serial number: 0404
- Airframe hours: 6154
- Engines: LYCOMING O-320-B2C 124 horsepower reciprocating
- Damage: Substantial damage
- Flight: Instructional, Part 91
- Operator: Watson Helicopters Inc.
- Registered owner: Tourtelot, Robert
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, January 12, 1991, 37 hours before
- Departed: WHP, PACOIMA, CA

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 30; commercial, flight instructor; medical: class 2, valid medical--no waivers/lim.; flight hours: 2,370 total, 2,351 in this make and model, 2,290 as pilot in command, 167.1 in the last 90 days, 102.5 in the last 30 days, 3.7 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 275° at 25 knots
- Visibility: 30 statute miles
- Lowest ceiling: none
- Temperature: 75 °F, dew point -0 °F

## 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 19910210002409A](https://openairdocs.org/incident/19910210002409A), Feb 10, 1991: Robsin R22ALPHA, Piru, CA, Substantial damage. Rotor RPM too low on practice power recovery from autorotation. Ground impact caused tail boom chopped and rollover

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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