Monday, August 08, 2016

Air Tractor AT-502B, N634LA: Fatal accident occurred August 08, 2016 in Hickory Ridge, Cross County, Arkansas

Aviation Accident Final Report - National Transportation Safety Board

The National Transportation Safety Board did not travel to the scene of this accident.

Additional Participating Entity:
Federal Aviation Administration / Flight Standards District Office; Little Rock, Arkansas
Air Tractor Inc; Olney, Texas

Investigation Docket - National Transportation Safety Board:

Location: Hickory Ridge, Arkansas
Accident Number: CEN16LA312
Date & Time: August 8, 2016, 14:15 Local
Registration: N634LA
Aircraft: AIR TRACTOR INC AT-502B 
Aircraft Damage: Substantial
Defining Event: Low altitude operation/event
Injuries: 1 Fatal
Flight Conducted Under: Part 137: Agricultural


During an aerial application flight, the airplane collided with a transmission line during a turn. The line became entangled with the airplane, and the airplane collided with terrain. Examination of the airplane did not reveal any preimpact anomalies that would have precluded normal operation of the airplane.

The pilot's medical certificate had expired several months before the accident. The pilot had been diagnosed with depression, diabetes mellitus, diabetes insipidus, hypogonadism, hypothyroidism, and hypoadrenalism; however, he had not reported any of these conditions or the medications used to treat them to the FAA. It is unlikely that the pilot's diabetes insipidus, hypogonadism, hypothyroidism, or
hypoadrenalism or their treatments contributed to the accident. However, his poorly controlled diabetes mellitus could have led to high blood sugar, which can result in blurred vision, or low blood sugar, which can slow psychomotor functioning Additionally, the pilot was known to have peripheral neuropathy with decreased sensation in his feet and a foot drop, which could have impaired his physical ability to use the rudder pedals. It could not be determined if the pilot's diabetes mellitus contributed to the accident. Further, the status of the pilot's psychiatric disease, including the severity of symptoms from his depression and any other psychiatric symptoms, around the time of the accident is unknown. Therefore, whether the pilot's psychiatric disease contributed to the accident could not be determined.

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The pilot's failure to maintain clearance from a transmission line while maneuvering at low altitude.


Environmental issues Wire - Response/compensation
Personnel issues Aircraft control - Pilot
Personnel issues Identification/recognition - Pilot
Aircraft Altitude - Not attained/maintained
Personnel issues Predisposing condition - Pilot
Environmental issues Wire - Awareness of condition

Factual Information

History of Flight

Maneuvering-low-alt flying Unknown or undetermined
Maneuvering-low-alt flying Low altitude operation/event (Defining event)
Maneuvering-low-alt flying Collision with terr/obj (non-CFIT)

On August 8, 2016, about 1415 central daylight time, an Air Tractor AT-502B, N634LA, impacted a bean field following a collision with a transmission line near Hickory Ridge, Arkansas. The commercial pilot was fatally injured, and the airplane was substantially damaged. The airplane was registered to and operated by Burnette Aviation, Inc., under the provisions of 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The local flight originated from a private airstrip at an undetermined time.

According to information collected by a Arkansas Highway Patrol trooper, the airplane was spraying a field when it collided with a transmission line during a turn. The transmission line got caught on the airplane's landing gear, and the airplane continued the turn before it impacted terrain.

Pilot Information

Certificate: Commercial 
Age: 61,Male
Airplane Rating(s): Single-engine land; Multi-engine land
Seat Occupied: Single
Other Aircraft Rating(s): None
Restraint Used: None
Instrument Rating(s): Airplane 
Second Pilot Present: No
Instructor Rating(s): None 
Toxicology Performed: Yes
Medical Certification: Class 2 With waivers/limitations 
Last FAA Medical Exam: January 29, 2014
Occupational Pilot: Yes 
Last Flight Review or Equivalent:
Flight Time: 19500 hours (Total, all aircraft)

The pilot held a commercial pilot certificate with ratings for single-engine land, multi-engine land, and instrument airplane. The pilot's logbook was not located during the investigation, and the pilot's total flight experience at the time of the accident could not be determined. 

The pilot was issued a second-class medical certificate on January 29, 2014, with the limitation "must wear corrective lenses and possess glasses for near and intermediate vision." Using this certificate, the pilot would not be able to exercise any airman privileges after January 31, 2016. On his application for this medical certificate, the pilot reported having accrued 19,550 total hours of flight experience of which 300 hours were in the preceding 6 months. He reported that he was not taking any medication, had no medical conditions other than kidney stones in 1991, and had no healthcare visits other than a flight physical in 2013.

Aircraft and Owner/Operator Information

Aircraft Make: AIR TRACTOR INC 
Registration: N634LA
Model/Series: AT-502B 
Aircraft Category: Airplane
Year of Manufacture: 2001 Amateur Built: No
Airworthiness Certificate: Restricted (Special)
Serial Number: 502B-0634
Landing Gear Type: Tailwheel
Seats: 1
Date/Type of Last Inspection: Unknown 
Certified Max Gross Wt.: 8000 lbs
Time Since Last Inspection:
Engines: 1 Turbo prop
Airframe Total Time: 6257 Hrs at time of accident 
Engine Manufacturer: P&W Canada
Engine Model/Series: PT6A Series
Registered Owner: 
Rated Power: 750 Horsepower
Operating Certificate(s) Held: Agricultural aircraft (137)
Operator Does Business As: BURNETTE AVIATION INC
Operator Designator Code: B6ZG

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual (VMC)
Condition of Light: Dawn
Observation Facility, Elevation: KJBR,262 ft msl 
Distance from Accident Site: 31 Nautical Miles
Observation Time: 13:53 Local
Direction from Accident Site: 34°
Lowest Cloud Condition: Clear
Visibility:  10 miles
Lowest Ceiling: None
Visibility (RVR):
Wind Speed/Gusts: 5 knots / 
Turbulence Type Forecast/Actual:  /
Wind Direction: 350°
Turbulence Severity Forecast/Actual:  /
Altimeter Setting: 29.93 inches Hg 
Temperature/Dew Point: 30°C / 19°C
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Hickory Ridge, AR 
Type of Flight Plan Filed: None
Destination: Hickory Ridge, AR 
Type of Clearance: None
Departure Time: 
Type of Airspace: 

Wreckage and Impact Information

Crew Injuries: 1 Fatal
Aircraft Damage: Substantial
Passenger Injuries:
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 1 Fatal
Latitude, Longitude: 35.399166,-91.001945(est)

The airplane was examined on-scene by inspectors from the Federal Aviation Administration (FAA) with the assistance of a representative from Air Tractor. All major components of the airplane were found at the accident site. The transmission line was entangled around the empennage and tailwheel. Flight control continuity was established from the cockpit controls to the elevators and rudder. The aileron controls were damaged and did not exhibit any preimpact anomalies. The flap controls were continuous, and the flaps were set to 5°. The pilot's restraints were found unbuckled. No anomalies consistent with a preimpact failure or malfunction were observed with the airframe or the engine.

Medical and Pathological Information

The Arkansas State Crime Laboratory, Little Rock, Arkansas performed an autopsy on the pilot. The cause of death was multiple blunt force injuries. According to the autopsy report, first responders noted that the pilot did not appear to have been wearing a safety helmet or pilot restraints.

The FAA's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicology testing on samples from the pilot. Testing was negative for carbon monoxide and ethanol. Testing detected acetaminophen, citalopram and its metabolite N-desmethylcitalopram, and pioglitazone in urine. Citalopram, N-desmethylcitalopram, and pioglitazone were also identified in heart blood.

Acetaminophen is a pain and fever medication available over the counter and commonly marketed as Tylenol; it is not impairing. Citalopram is a prescription antidepressant commonly marketed as Celexa. Pioglitazone is a prescription medication used to treat diabetes.

While citalopram is not generally considered impairing, its use indicates that the pilot was being treated for depression, which is associated with significant cognitive degradation, particularly in executive functioning. As a result, depression is a disqualifying condition for pilot medical certification. The FAA will consider a special issuance of a medical certificate to a depressed pilot after 6 months of treatment if the applicant is clinically stable on an approved medication.

Pioglitazone is not directly impairing, but the FAA requires regular additional evaluations of diabetic pilots to ensure their diabetes is properly controlled and they do not have neurologic, renal, or ophthalmologic complications of the disease that might impair their ability to safely fly an aircraft. If specific criteria are met for the control of this disease, a pilot may be issued a medical certificate.

Review of personal medical records from the pilot's endocrinologist showed that he had been diagnosed with type 2 diabetes mellitus in 2006. In 2009, he had brain surgery to remove a large tumor on his pituitary gland. As a result, he lost regulation of the hormonal systems usually controlled by the pituitary gland. He began to take replacement hormones for hypoadrenalism, hypothyroidism, hypogonadism, and diabetes insipidus immediately after the surgery. Over the ensuing years, the pilot developed peripheral neuropathy and kidney dysfunction from his chronic, poorly controlled diabetes mellitus. At one point, he burned his foot because he could not feel it, and he developed a right foot drop. The records indicated that the pilot refused to consider using insulin to treat his diabetes mellitus because it would not be allowed by the FAA.

At his most recent endocrinology visit in April 2016, the pilot's medications included: citalopram; desmopressin (a hormone that treats diabetes insipidus); glimepiride, metformin, pioglitazone, and Victoza to treat his diabetes mellitus; hydrocortisone (to replace cortisol); levothyroxine (thyroid replacement); and pregabalin (a potentially impairing medication used to treat chronic nerve pain due to diabetes).

One of the pilot's family members made a call to the FAA safety hotline in March 2016 reporting that the pilot was falling frequently and having trouble getting up afterward, taking "heavy duty psych meds," and having fits of rage where he would threaten to crash his airplane into a variety of targets. In April 2016, the family member made an email report to the FAA describing the pilot's medical
conditions. The FAA requested information from the pilot in April 2016. This issue was being evaluated by the FAA at the time of the accident.

NTSB Identification: CEN16LA312
14 CFR Part 137: Agricultural
Accident occurred Monday, August 08, 2016 in Hickory Ridge, AR
Aircraft: AIR TRACTOR INC AT-502B, registration: N634LA
Injuries: 1 Fatal.

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

On August 8, 2016, about 1415 central daylight time, an Air Tractor AT-502B airplane, N634LA, impacted a bean field following a collision with a transmission line near Hickory Ridge, Arkansas. The commercial rated pilot was fatally injured and the airplane was substantially damaged. The airplane was registered to and operated by Burnette Aviation Inc. under the provisions of 14 Code of Federal Regulations Part 137 as an aerial application flight, which operated without a flight plan. The local flight originated from a private airstrip at an unknown time.

According to initial information obtained by investigators, the airplane was spraying a field when it collided with a transmission line during a turn. The transmission line got caught on the airplane's landing gear and the airplane continued the turn before it impacted terrain.

The airplane was retained for further examination.

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