History of Flight
On August 1, 2014, about 0900 Pacific daylight time, a Schweizer Aircraft Corporation G-164B, registration N3627R, impacted terrain after striking a set of power distribution lines near Tulelake, California. The airplane was operated by Macy's Flying Service as an aerial application flight under 14 CFR Part 137. The commercial pilot was fatally injured; the airplane sustained substantial damage and was subsequently destroyed by post-impact fire. The flight departed Tulelake Municipal Airport about 0820. Visual meteorological conditions prevailed, and no flight plan had been filed.
Responding officers from the Siskiyou County Sheriff's Department found the airplane in an alfalfa field, 500 ft north of severed overhead power distribution lines. The airplane rested on a south heading; the cabin had been consumed by fire after extensive crush damage. All four wings were partially detached from the airframe, and the left top wing was folded over the vertical stabilizer.
The pilot was applying insecticide to an alfalfa field, and the accident occurred on one of the last passes.
Personnel Information
The 58-year-old pilot held a commercial pilot certificate with ratings for airplane single-engine land and instrument airplane. He was issued a second-class medical certificate on September 7, 2013, with a limitation requiring corrective lenses. On that application, he reported 30,000 total flight hours. The operator reported 504 hours in the accident airplane in the preceding 90 days.
Aircraft Information
The tailwheel-equipped airplane was manufactured in 1983 as a restricted agriculture and pest control category biplane. It was equipped with a 715 shaft horsepower Garrett/Airesearch TPE331-2 turboprop engine driving a three-blade controllable pitch Hartzell propeller. The airplane's height was 10 ft 9 inches.
Meteorological Information
An automated surface observation at Klamath Falls Airport (elevation 4,095 ft, 14 miles northeast of the accident site) issued 7 minutes before the accident indicated calm wind, visibility 10 miles or greater, clear skies, temperature 22°C, dew point 10°C, and altimeter setting 30.14 inHg. According to the U.S. Naval Observatory, at 0900 near Tulelake, the sun's altitude was 31.8°, azimuth 94.0°.
Medical and Pathological Information
An autopsy by the Siskiyou County Office of the Sheriff/Coroner reported the cause of death as thermal injury due to an airplane crash, with an anatomic finding of soot in the larynx and trachea. Toxicological tests performed by the FAA Civil Aerospace Medical Institute detected 16 percent carbon monoxide in the pilot's blood; tests for drugs and alcohol were negative.
Tests and Research
Examination of the recovered engine and airframe by the NTSB investigator-in-charge revealed the empennage intact, with other components showing extensive fragmentation, thermal, and crush damage. The flight control system was functionally intact despite multiple breaches. A 25-ft-long section of copper cable was found entwined in the leading edge of the upper right wing. The engine had separated from its mount, and the gearbox had detached. The exhaust stack displayed light brown sooting but no cracks or indentations from internal blade liberation. The inlet compressor wheel was intact, manually rotatable, and turned smoothly with corresponding gear movement. The propeller hub remained attached with two blades exhibiting leading edge gouges, chordwise scratches, and twist; the third blade was separated but similarly damaged. No anomalies were found that would have precluded normal operation.
The power distribution lines were owned by Pacific Power. Poles about 40 ft tall, oriented east-west, spanned 300 ft. Three high-voltage transmission lines were at the top; four thinner under-build lines hung 30 ft 6 inches above ground. The lower lines had been severed about 50 ft east of the west pole; the higher lines were undamaged.
A spotter had been assigned to the pilot but did not witness the accident, as he was transitioning to another location. According to the operator, the pilot was familiar with the field and had flown under the lines many times; it was likely he chose to fly under them because they were very high relative to the field.
Regulatory Context
FAA regulations (14 CFR Part 137.29) allow agricultural aircraft operators to deviate from Part 91 provisions without a waiver for dispensing operations. Advisory Circular AC 137-1A provides guidance for flying under wires.