Amateur-built THUNDER GULL J accident near Santa Margarita, California, August 24, 1991
On August 24, 1991 at about 6:25 pm local time, a amateur-built THUNDER GULL J (ultralight), registered UNREG, was destroyed in an accident near Santa Margarita, California. It was a flight of an unrecorded kind under general aviation rules (Part 91). 1 person was seriously injured and 1 person had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
THE FAILURE OF THE WING SPAR WHEN THE DESIGN LIMITS OF THE AIRPLANE WAS EXCEEDED BY THE PILOT. CONTRIBUTING TO THE ACCIDENT WAS AN INADEQUATE AIRFRAME DESIGN AND AN ABRUPT MOVEMENT OF THE FLIGHT CONTROLS BY THE PILOT.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- August 24, 1991 · about 6:25 pm local time
- Place
- Santa Margarita, California · map
- Type
- Accident
- Injuries
- 1 person was seriously injured and 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built THUNDER GULL J THUNDER GU
- Registration
- UNREG · no longer on the register · serial 1
- Damage
- Destroyed
- Flight
- Flight of an unrecorded kind · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
THE CERTIFICATED PRIVATE PILOT AND A PASSENGER WERE CONDUCTING A FLIGHT TEST OF AN UNREGISTERED, HOMEBUILT AIRPLANE. THE AIRPLANE WAS BEING MARKETED AS AN ULTRALIGHT VEHICLE WITH AN EXCEPTION OF THE ULTRALIGHT REGULATIONS GRANTED TO THE EXPERIMENTAL AIRCRAFT ASSOCIATION. THE PILOT WAS PERFORMING AEROBATIC MANEUVERS WHILE THE PASSENGER WAS FILMING THE EVENT FROM THE REAR SEAT. DURING THE PULL-UP PORTION OF AN IMMELMAN MANEUVER, THE LEFT WING FAILED AND FOLDED UPWARDS. THE PILOT DEPLOYED A BALLISTIC PARACHUTE TO CONTROL THE AIRPLNE'S DESCENT. AS THE PARACHUTE DEPLOYED, IT BECAME ENTANGLED WITH THE ENGINE PROPELLER AND WAS DAMAGED AND ONLY PARTIALLY INFLATED. THE AIRPLANE DESCENDED AND STRUCK THE GROUND AT ABOUT 50 MPH. THE AIRPLANE AND PILOT DID NOT QUALIFY FOR THE CONDITIONS OF THE ULTRALIGHT REGULATION EXEMPTION, AND THE VEHICLE IS CONSIDERED TO BE AN AIRPLANE.
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: private
- Ratings: single-engine land
- Flight time: 3,000 hours in all; 60 in the last 90 days; 41 in the last 30 days
- Medical certificate: None (expired)
- Seat: frt
The aircraft
- Airframe total time: 41 hours
- Last inspection: inspection type not recorded, January 2, 2000
- Maximum gross weight: 800 lb
- Seats: 2
- Landing gear: fixed
- Engine: Bombardier ROTAX 503 (piston); 0 hours total
The flight
- Departed from: NONE Santa Margarita CA at 6:15 pm
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Visibility: 20 statute miles
- Sky: clear
- Temperature: 100°F (38°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 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.
Other NTSB records under UNREG the same tail number, which may have belonged to a different aircraft at the time
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.