Air Tractor 502A accident near Queen Creek, Arizona, April 22, 2000
On April 22, 2000 at about 5:19 pm local time, a Air Tractor 502A, registered N15466, was destroyed in an accident near Queen Creek, Arizona. It was an aerial application (crop spraying) flight under agricultural flying rules (Part 137). 1 person was killed. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The fatigue failure and in-flight separation of the left wing due to the manufacturer's underestimation during the aircraft design process of the time interval from fatigue crack initiation to failure, and, the manufacturer's subsequent specification of an inadequate inspection interval.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 22, 2000 · about 5:19 pm local time
- Place
- Queen Creek, Arizona
- Type
- Accident
- Injuries
- 1 person was killed.
- Weather
- visual conditions (good weather)
- Aircraft
- Air Tractor 502A
- Registration
- N15466 · no longer on the register · serial 502A-0181
- Damage
- Destroyed
- Flight
- Aerial application (crop spraying) flight · agricultural flying rules (Part 137)
The NTSB's narrative final · quoted from the NTSB record
The airplane was spraying chemicals on a field of crops when the left wing separated in flight. Ground witnesses said that the airplane was making a level spray pass over a potato crop when the left wing failed. No unusual meteorological phenomena were observed in the area, and the airplane did not perform any unusual maneuvers prior to the failure. The left wing's lower spar cap was found to have fractured in fatigue at a point that transected the inboard attach block bolt hole where the spar attaches to the center section spar carry through member. Multiple origin sites were identified within the bolt hole bore, with corrosion pitting evident at the origin points. The spar caps met the hardness, chemistry, and microstructure of the production drawing specified material. Air Tractor Service Letter 118 and the maintenance manual specify an inspection procedure, which calls for the removal of the hopper for a detailed inspection of the spar caps for cracks; one area identified as critical for cracking was the inboard bolt hole bore. The inspection interval was specified as every 2,000 hours or 3 years. The number of crack arrest striations in the fatigue region was determined from the first point the crack would be visible from beneath the attach block during the specified inspection, and the mean time for the fatigue crack to progress from detectible during the inspection to failure was calculated to be about 105 hours. Examination of the right wing lower spar cap revealed the presence of multiple fatigue cracks emanating from corrosion pits within the outboard bolt hole bore. No maintenance records were located for either the airframe or engine. A mechanic was located who performed some periodic maintenance on the aircraft. He stated that during the removal of the hopper in May 1997, 2 years 11 months prior to the accident, he had accomplished the 2,000-hour check of the wing spars in the area of the attach bolts as required by Service Letter 118. Based on other records, the aircraft was believed to have flown an average of 500 hours per year and would have accumulated only 1,500 hours since the inspection.
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: airplane multi-engine; instructor: airplane single-engine; instrument: airplane
- Flight time: 26,190 hours in all
- Medical certificate: Class 2 (valid medical--no waivers/lim.)
- Seat: ctr
The aircraft
- Last inspection: inspection type not recorded
- Maximum gross weight: 8,000 lb
- Seats: 1
- Landing gear: fixed
- Engine: P&W PT6A-45A (turboprop); 0 hours total
- Operator: San Tan Dusters, INC.
The flight
- Departed from: Higley AZ at 5:00 pm
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 250° at 7 knots
- Visibility: 30 statute miles
- Sky: clear
- Temperature: 151°F (66°C), dew point 113°F (45°C)
- Altimeter: 29.00 inHg
- Observation at 5:32 pm from IWA, 5 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| 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.