HISTORY OF FLIGHTOn June 21, 2011, about 0515 mountain daylight time, an Air Tractor AT-301, N3661B, collided with terrain in a field near Hogeland, Montana. The pilot was operating the airplane under the provisions of Title 14 Code of Federal Regulations Part 137 as an aerial application flight. The commercial pilot sustained fatal injuries. The airplane sustained substantial damage to the forward fuselage and both wings. The local flight departed Harlem Airport, Harlem, Montana, about 0500. Visual meteorological conditions prevailed, and no flight plan had been filed. Two witnesses, who were located in their house next to the accident site, heard an airplane approach at 0515. The noise became louder and was followed by a sound that they described as consistent with an airplane turning. A few seconds later they heard a "thud". One of the witnesses responded, and found the airplane in an adjacent field. PERSONNEL INFORMATIONThe 65-year-old-pilot held a commercial pilot certificate with ratings for airplane single-engine land, and a private certificate with ratings for multiengine land. Because he did not hold an instrument rating, the certificate was issued with limitations that it was not valid for carriage of persons for hire on cross-country flights more than 50 nautical miles, or at night. Examination of the pilot's Federal Aviation Administration (FAA) airman medical records revealed that he applied for a second-class medical certificate on May 25, 2011, but was inadvertently issued a third-class certificate. The certificate had limitations that he must wear corrective lenses. Flight records were not recovered for the pilot; however, at the time of application for his medical certificate he reported a total pilot time of 6,350 hours, 40 of which occurred in the preceding 6 months. Various family members reported that the pilot was both under financial, work, and personal stress. He was self-employed as an agricultural pilot; he was a mortician and the local coroner, and he owned and operated a funeral home. As his son was due to be married later that year, he had been involved in preparations for the wedding. Additionally, he had changed his diet earlier in the year. One of his siblings reported that during a telephone conversation the week prior to the accident he sounded tired and in a state of malaise; during the conversation he sounded "dis-jointed and out of character," and he further stated that he was "...getting tired of flying." AIRCRAFT INFORMATIONThe low-wing, tailwheel equipped, fixed-gear airplane, was manufactured in 1981. It was powered by a Pratt and Whitney R1340-AN1 radial engine, driving a Hamilton Standard two-blade constant-speed propeller. No maintenance records were recovered for the airplane, however, an FAA "Major Repair and Alterations" form (337), dated April 2002 indicated that in 1997 a Horizon Instruments, model P-1000 tachometer was installed. The tachometer was examined following the accident, and indicated a total time of 5,617 hours. The airplane was equipped with a SATLOC GPS enabled agricultural guidance system. The unit sustained crush damage and was sent to the NTSB office of research and engineering for data extraction. Examination revealed that the memory card utilized to store positional data had not been installed, and as such, no flight data had been recorded. METEOROLOGICAL INFORMATIONThe closest aviation weather observation station was located at Havre City-County Airport, Havre, Montana, which was 57 statute miles (sm) southwest of the accident site. The elevation of the weather observation station was 2,592 feet mean sea level (msl). An aviation routine weather report (METAR) for Havre was recorded at 0453. It reported: winds from 180 degrees at 7 knots; visibility 10 miles; sky clear; temperature 9 degrees Celsius (C); dew point 8 degrees C; altimeter 29.92 inches of mercury. According to the U.S. Naval Observatory Astronomical Applications Department, civil twilight and sunrise occurred at 0434 and 0517, respectively, in the city of Havre. AIRPORT INFORMATIONThe low-wing, tailwheel equipped, fixed-gear airplane, was manufactured in 1981. It was powered by a Pratt and Whitney R1340-AN1 radial engine, driving a Hamilton Standard two-blade constant-speed propeller. No maintenance records were recovered for the airplane, however, an FAA "Major Repair and Alterations" form (337), dated April 2002 indicated that in 1997 a Horizon Instruments, model P-1000 tachometer was installed. The tachometer was examined following the accident, and indicated a total time of 5,617 hours. The airplane was equipped with a SATLOC GPS enabled agricultural guidance system. The unit sustained crush damage and was sent to the NTSB office of research and engineering for data extraction. Examination revealed that the memory card utilized to store positional data had not been installed, and as such, no flight data had been recorded. WRECKAGE AND IMPACT INFORMATIONThe airplane was located about 90 feet from a residence, at the border of the field to be sprayed. There were no ground scars or debris leading up to the airplane, which was located in its entirety within the confines of the accident site. The ground surface was comprised of hard packed soil, rocks, and stones. It had come to rest nose-down, with the fuselage sustaining diagonal crush damage focused on the left side from the firewall through to the aft cabin. The hopper was completely fragmented, and the fuselage had rolled about 45 degrees to the left over the left wing. The tail cone was still attached, and canted 15 degrees further to the left. The vertical stabilizer and rudder remained attached, and the right horizontal stabilizer and elevator had separated from the tailcone, coming to rest behind the right wing. The left horizontal stabilizer and elevator remained attached, and exhibited 90-degree upward bending mid-span. The left wing sustained accordion-like crush damage perpendicular to the chord, from the leading edge through to the aft spar. The right wing sustained crush damage limited to the lower portion of the leading edge. During recovery, the engine was located buried in about 3 feet of dirt below the firewall. The propeller sustained leading edge nicks, gouges, and scratches with both tips twisted about 90 degrees. ADDITIONAL INFORMATIONWeight and Balance The purpose of the flight was to apply a herbicide (trade name Vendetta), which contained Bromoxynil, Isooctyl Ester of MCPA, and Naphthalene. The FAA inspector who responded to the accident site utilized the pilot's weight, the airplane's fuel load, and the amount of herbicide mixture required to cover the field, and calculated that the total weight at the time of the accident was about 7,115 pounds. The flight manual listed a maximum certified takeoff weight of 5,000 pounds, but allowed for an increase in maximum weight by reference to the Civil Aeronautics Manual (CAM) 8. Utilizing this manual, the airplane's maximum recommended operating weight was calculated to be 6,550 pounds. Performance The FAA approved airplane flight manual for the Air Tractor AT-301 series states the following regarding the use of flaps during agricultural application: "Flaps may be used as a turning-aid, provided small deflections are used (5 to 8 degrees). The usual method of using flaps is to make the pull-up and initial bank with flaps retracted. As the aircraft is being banked to turn back into the field, touch the flap switch briefly and let off a little back pressure on the stick, as the flaps cause a slight pitch up tendency. Continue the turn, and as you line up for your pass, retract the flaps." MEDICAL AND PATHOLOGICAL INFORMATIONA postmortem examination was conducted by the State of Montana Forensic Science Division, Missoula, Montana. The cause of death was reported as the effect of blunt force injuries. Toxicological tests on specimens recovered from the pilot by the medical examiner, were performed by the FAA Civil Aerospace Medical Institute (CAMI). Analysis revealed no findings for carbon monoxide, or cyanide. The results were negative for ingested alcohol, with the following positive results: >> 0.045 (ug/mL, ug/g) Desmethylsertraline detected in Blood (Femoral) >> Desmethylsertraline detected in Urine >> Ibuprofen detected in Urine >> 0.014 (ug/mL, ug/g) Sertraline detected in Blood (Femoral) >> Sertraline detected in Urine Refer to the toxicology report included in the public docket for specific test parameters and results. According to CAMI, Sertraline (trade name Zoloft) is used for the symptomatic relief of depressive illness, with a therapeutic low of 0.0100 ug/mL and high of 0.200 ug/mL. The pilot did not report either the medication or a history of depressive illness on any of his applications for a medical certificate. Review of the pilot's personal medical records did not reveal any diagnosis or treatment for a depressive illness, nor any information regarding the prescription of Sertraline. The pilot's daughter stated that he had been taking the medication for about 6 months, and that it had been prescribed by his sister-in-law, who was a Nurse Practitioner. TESTS AND RESEARCHThe airframe was removed from the accident site and examined by an FAA inspector and representatives from Air Tractor. Flight and engine control continuity was confirmed, and the flap actuator had extended 3 3/8 inches, which according to the Air Tractor representative corresponded to the flaps full-down position. No anomalies were noted to the airframe or engine which would have precluded normal operation. See the public docket for a detailed report.