Amateur-built ZODIAC 601 XL accident near Antelope Island, Utah, March 3, 2009
On March 3, 2009 at about 3:40 pm local time, a amateur-built ZODIAC 601 XL, registered N3683X, was substantially damaged in an accident during enroute (cruise) near Antelope Island, Utah. It was a personal flight under general aviation rules (Part 91). 1 person was killed. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The in-flight failure of both wings due to aileron flutter. The aileron flutter was the result of inadequate wing stiffness and the lack of aileron counterbalances.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- March 3, 2009 · about 3:40 pm local time
- Place
- Antelope Island, Utah · map
- Type
- Accident
- Injuries
- 1 person was killed.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built ZODIAC 601 XL
- Registration
- N3683X · no longer on the register · serial 6-5136
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
Radar data and a performance study depicted the airplane flying on a steady northerly course adjacent to mountains at 113 knots calibrated airspeed. The pilot changed course slightly to fly close to or over the mountains. The airplane subsequently experienced an in-flight breakup. All of the airplane's structural components and flight control surfaces were located at the main impact site. There was no evidence of excessive airspeed or maneuvers that would lead to a structural overload and failure of the wings. Turbulence was present in the area, although it was not believed to be severe and likely did not contribute to the failure. An examination of the airplane wreckage revealed that the left wing spar had buckled upward near the fuselage and the left wing had wrapped around the fuselage near the cockpit. There was compression buckling of the lower spar cap of the left wing's rear spar and compression buckling of the upper and lower spar caps of the right wing's rear spar. The compression damage to both rear spars and the upward buckling of the left wing's main spar are evidence of upward and downward bending of both wings. The upward and downward bending of the wings is consistent with aerodynamic flutter. The structural loading at the inboard section of the left wing was further increased as the trailing edges of the outboard sections moved up and down. Ultimately the left wing failed as it bent upward near the root. Aerodynamic flutter can occur when there is insufficient stiffness in the structure or when the flight controls are not mass-balanced. Counterbalanced flight controls can protect less stiff surfaces at higher airspeeds. The ailerons did not have counterbalances, which would have offered direct protection from aerodynamic flutter.
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
What happened, in order
- Aircraft structural failure during enroute (cruise) defining event
- Loss of control in flight during enroute (cruise)
- Collision with terrain or object (not controlled flight into terrain) during uncontrolled descent
The NTSB's findings
- cause Aircraft › Aircraft structures › Wing structure › (general) › Failure
- cause Aircraft › Aircraft structures › Wing structure › (general) › Design
- cause Aircraft › Aircraft structures › Wing structure › Ailerons › Failure
- cause Aircraft › Aircraft structures › Wing structure › Ailerons › Design
Pilot
- Certificate: commercial pilot
- Ratings: multi-engine land; single-engine sea; instrument: airplane
- Flight time: 350 hours in all; 14 in this make and model
- Last flight review: August 20, 2007
- Medical certificate: Sport Pilot (without waivers/limitations)
- Seat: left
- Injury: fatal
The aircraft
- Airframe total time: 14 hours
- Last inspection: condition inspection, November 11, 2008
- Seats: 2
- Landing gear: fixed
- Engine: Jabiru 3300 (piston); 0 hours total
The flight
- Departed from: KTVY Tooele UT at 3:18 pm
- Destination: BTF Bountiful UT
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 160° at 17 knots
- Visibility: 10 statute miles
- Sky: broken clouds at 20,000 ft; a few clouds at 7,000 ft
- Temperature: 55°F (13°C), dew point 32°F (0°C)
- Altimeter: 29.93 inHg
- Observation at 3:53 pm from KSLC, 17 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 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.