History of Flight
On December 1, 2016, at 1629 central standard time, a Cessna 340, registration N123KK, impacted terrain about 10 miles south of Hector International Airport (FAR), Fargo, North Dakota. The pilot reported an in-flight fire before the crash. The airplane was destroyed and the pilot was fatally injured. The flight was operated by Weather Modification, LLC, under 14 CFR Part 91 as an "other work use" flight. Visual meteorological conditions prevailed, and an IFR flight plan was filed. The flight originated from FAR around 1430.
The pilot was under contract with NOAA to collect air samples at various altitudes over oil fields near Carrington, North Dakota, and was returning to FAR. Radar data and communications transcripts indicate the pilot was being vectored toward the FAR runway 36 localizer but overshot it. Shortly after, at an altitude of 1,700 feet MSL, he reported an onboard fire. The airplane subsequently lost altitude and radar contact was lost.
Personnel Information
The 55-year-old pilot held a commercial pilot certificate with airplane single- and multi-engine land ratings, a Beech 300 type rating, and a flight instructor certificate with single-engine, multi-engine, and instrument ratings. He also held a mechanic's certificate with airframe and powerplant ratings. His most recent first-class medical certificate, dated May 5, 2016, required glasses for near and intermediate vision.
According to the pilot's logbook, he had accumulated 7,897.6 total flight hours, including 6,920.0 multiengine, 1,998.8 turbine, 1,637.7 actual instrument, 108.3 simulated instrument, and 79.0 flight simulator hours. His last flight review was completed on March 1, 2016, in the accident aircraft.
Aircraft Information
The Cessna 340, serial number 340-0251, was manufactured in 1973 and powered by two Continental TSIO-520-JB engines with 1,400-hour time-between-overhaul limits. Both engines had been overhauled; the left in March 2014 and the right in September 2012. The last annual inspection occurred on July 27, 2016, at a total time of 7,012.6 hours. The airplane was last certified for instrument flight on August 2, 2016.
The aircraft was equipped with a Stewart Warner combustion heater (Janitrol) mounted in the right front section of the nose baggage compartment. It also carried a NOAA air sampling system manufactured by High Precision Devices, stored in two plastic boxes: one with glass jars for samples, the other containing a compressor package with battery, compressors, circuit boards, and tubing. The boxes were strapped to seat tracks behind the copilot's seat. NOAA representatives stated the system had been in use for 12 years at 14 locations with no previous fire reports.
Meteorological Information
Weather recorded at FAR at 1646, about 16 minutes after the accident, reported wind from 340° at 12 knots, visibility 9 miles, overcast ceiling at 1,500 feet, temperature 0°C, dew point -2°C, and altimeter 29.99 inches of mercury.
Wreckage and Impact Information
The accident site was in an open field about 10 miles south of FAR at an estimated elevation of 900 feet MSL, bordered by trees and a ravine to the east. The nose baggage compartment doors were found about 2 miles south of the main wreckage. The wreckage path was on a magnetic heading of 197°. Ground scars and impact damage indicated a high-velocity impact at a low angle with a left-wing-low and nose-up attitude. Initial ground contact showed left propeller slash marks, followed by fuselage and right propeller marks. The aircraft became airborne briefly before sliding into trees. The right wing outboard and empennage separated; no soot or molten metal was found on the empennage. The fuselage came to rest inverted about 550 feet from initial impact.
Flight control cables were connected and exhibited tension overload separations or were cut by first responders. The mid-fuselage aileron bellcrank and flap motor were consumed by fire. Both fuel selector handles were consumed; the left valve position was undetermined, the right valve was off. No smoke streaking or heat damage was noted at the heater connection. The combustion heater was found intact, impact-damaged, sooted, with no explosion signs. Flight instruments and switches were damaged or consumed by post-impact fire. The main circuit breaker bus bars showed no hot spots. Engine fuel and oil pressure lines had no pre-impact fire evidence.
Additional Information
The aircraft carried two hand-held fire extinguishers: one halon and one halotron, each with about 5.4 pounds of agent. One had been discharged; the other appeared to have exploded. According to Textron Aviation, the Cessna 340 has a pressurized volume of about 250 cubic feet. FAA technical information notes that halon does not displace oxygen at low concentrations but can be cardiotoxic and narcotic at high concentrations. A total release of 5.4 pounds would significantly exceed the recommended agent volume for that cabin size.
Medical and Pathological Information
An autopsy attributed death to multiple injuries. Toxicological analysis of blood was negative for ethanol, drugs, and cyanide; a small amount of carbon monoxide (6% saturation) was detected. FAA tests found no carbon monoxide, cyanide, ethanol, or drugs in heart blood. No tests were conducted for halon or halotron.
Tests and Research
The wreckage was examined at Weather Modification's hangar. The NOAA compressor package was examined at the NTSB Materials Laboratory; all smoke and heat damage originated externally, with no evidence that the air sampling system caused the in-flight fire. The combustion heater showed thermal discoloration and soot from external fire, no fuel leaks, but one fuel fitting was loose. Plexiglas windshield pieces showed soot streaks on the outside, indicating smoke origin upstream of the windshield and before its breakup. The nose baggage compartment doors lacked soot, thermal damage, or deformation consistent with a high-energy explosion.