# NTSB LAX92FA025: Aerospatiale AS350B, N9001S, Scottsdale, AZ, October 26, 1991

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Field investigation · Final report
- Date: October 26, 1991, 15:15 local (22:15 UTC)
- Place: Scottsdale, AZ
- Coordinates: 33.609508, -111.889984 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=33.6095&lon=-111.8900&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 2 minor, 1 uninjured
- Status: Completed, report May 3, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 27388
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX92FA025
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/27388/pdf
- Page: https://openairdocs.org/ntsb/LAX92FA025

## Probable cause

AN UNDETERMINED MALFUNCTION OF THE HYDRAULIC SYSTEM IN WHICH THE SYSTEM WAS LOCKED, PREVENTING THE MOVEMENT OF THE FLIGHT CONTROLS, AND LOSS OF DIRECTIONAL CONTROL.

## Sequence of events

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

- Airframe/component/system failure/malfunction, hover
  - hydraulic system - locked (cause)
  - hydraulic system - undetermined (cause)
- Loss of control - in flight, hover
  - flight controls - not possible, pilot in command (contributing factor)
  - directional control - not possible, pilot in command (contributing factor)
- In flight collision with terrain/water, hover
  - terrain condition - ground

## Analysis

THE CERTIFICATED COMMERCIAL PILOT/CERTIFIED FLIGHT INSTRUCTOR WAS CONDUCTING TRAINING WITH A SECOND PILOT IN HELICOPTER EMERGENCY PROCEDURES, THAT INCLUDED HYRAULICS OFF LANDINGS. ON THE THIRD LANDING WITHOUT HYRAULIC BOOST PRESSURE, AT AN AIRSPEED OF ABOUT 2 KNOTS AND A SKID HEIGHT OF ABOUT 1 FOOT, THE HELICOPTER BEGAN AN UNCOMMANDED TURN TO THE LEFT. THE PILOT ATTEMPTED TO COUNTER THE TURN BUT WAS UNABLE TO MOVE THE FLIGHT CONTROLS. THE HELICOPTER'S LEFT BANK ANGLE, NOSE DOWN ATTITUDE AND LEFT TURN CONTINUED UNTIL THE MAIN ROTOR BLADES STRUCK THE GROUND. THE LEFT FRONT PORTION OF THE FUSELAGE AND SKID TUBE THEN STRUCK THE GROUND. AN EXAMINATION OF THE HYDRAULIC SYSTEM, INCLUDING DISASSEMBLY OF THE MAIN ROTOR CONTROL SERVOS, FAILED TO LOCATE THE CAUSE OF THE MALFUNCTION.  THIS IS THE SECOND RPTD HYD OFF FLT CONTROL SEIZURE THAT RESULTED IN AN ACCIDENT.  THE FLT CREW OF BOTH HELICOPTERS WERE WELL QUALIFIED.

## Aircraft

- Registration: [N9001S](https://openairdocs.org/deregistered/N9001S-2013-05-17), registration cancelled 2013-05-17, S/N 1022, built 1978 (OpenAirDocs)
- Reported make and model: AEROSPATIALE AS350B
- Registry model: [Aerospatiale AS350B](https://openairdocs.org/model/aerospatiale-as350b) (registry code 8680800) (OpenAirDocs)
- Registry engine: [Lycoming LTS-101 series](https://openairdocs.org/engine/lycoming-lts-101-series) (registry code 41560, turbo-shaft) (OpenAirDocs)
- Category: Helicopter
- Serial number: 1022
- Airframe hours: 6641
- Engines: TURBOMECA ARRIEL 1B 641 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Instructional, Part 91
- Operator: Lone Eagle Aviation, Inc., doing business as Eagle Rescue Of Arizona
- Registered owner: Mark A. Berlin Trustee
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, October 21, 1991, 23 hours before
- Departed: SDL, SCOTTSDALE, AZ
- Flight plan: Company VFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 37; commercial, flight instructor; airplane ratings: multi-engine land, single-engine land; instrument ratings: helicopter, airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 8,248 total, 312 in this make and model, 8,185 as pilot in command

## Weather

- Conditions: Visual (VMC), Day
- Wind: 180° at 7 knots
- Visibility: 40 statute miles
- Lowest ceiling: none
- Temperature: 77 °F, dew point 37 °F
- Altimeter: 29.00 inHg
- Observed at: SDL, 5 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 19911026048079A](https://openairdocs.org/incident/19911026048079A), Oct 26, 1991: Snias AS350B, Scottsdale, AZ, Substantial damage. Lost control during hydraulics off demo landing. Failed to check left turning tendency in near hover touchdown.

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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