Aerospatiale AS350B accident near Scottsdale, Arizona, October 26, 1991
On October 26, 1991 at about 10:15 pm local time, a Aerospatiale AS350B (helicopter), registered N9001S, was substantially damaged in an accident near Scottsdale, Arizona. It was an instructional flight under general aviation rules (Part 91). 2 people had minor injuries; 1 other was unhurt. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
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.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- October 26, 1991 · about 10:15 pm local time
- Place
- Scottsdale, Arizona · map
- Type
- Accident
- Injuries
- 2 people had minor injuries; 1 other was unhurt.
- Weather
- visual conditions (good weather)
- Aircraft
- Aerospatiale AS350B · all AS350Bs on the register
- Registration
- N9001S · registry record · serial 1022
- Damage
- Substantial damage
- Flight
- Instructional flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
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.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
Pilot
- Certificate: flight instructor, commercial pilot
- Ratings: multi-engine land; single-engine land; instructor: helicopter; instrument: airplane; instrument: helicopter; rotorcraft: helicopter
- Flight time: 8,248 hours in all; 312 in this make and model; 8,185 as pilot in command; 333 on instruments
- Medical certificate: Class 1 (valid medical--no waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 6,641 hours
- Last inspection: annual inspection, October 21, 1991; 23 hours since
- Maximum gross weight: 4,300 lb
- Seats: 5
- Landing gear: fixed
- Engine: Turbomeca ARRIEL 1B (turboshaft); 0 hours total
- Operator: Lone Eagle Aviation, INC.
The flight
- Departed from: SDL Scottsdale AZ at 9:30 pm
- Runway 0
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: from 180° at 7 knots
- Visibility: 40 statute miles
- Sky: scat at 25,000 ft
- Temperature: 77°F (25°C), dew point 37°F (3°C)
- Altimeter: 29.00 inHg
- Observation at 10:46 pm from SDL, 5 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | 1 | ||
| Passengers | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.