N8347ZCessna 210-5 · 1963

On October 16, 2017, about 1430 Alaska daylight time, a Cessna 210-5 airplane, N8347Z, impacted the Yukon River about 10 miles southwest of Russian Mission, Alaska. The private pilot sustained fatal injuries, and the airplane was destroyed. The airplane was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. Instrument meteorological conditions prevailed at the accident site. No flight plan had been filed for the visual flight rules (VFR) flight, and no record of the pilot receiving a preflight weather briefing could be found. The flight originated about 1415 from Kako Airport, Kako, Alaska, with a destination of Bethel Airport (PABE), Bethel, Alaska.

Visual meteorological conditions were reported at the time of departure. According to a pilot of an airplane that departed about 10 minutes ahead of the accident airplane on the same route of flight and also destined for Bethel, widespread areas of low-level fog (between 400 and 600 ft above ground level [agl]) existed along the route. This pilot stated, during a postaccident interview, that he conversed with the accident pilot (after he departed from Kako) about the fog layers. No further radio communications occurred between the pilots. The interviewed pilot indicated that he tried to contact the accident pilot about 15 minutes after their conversation but received no response. After arriving at PABE and loading passengers, the interviewed pilot departed for a return flight to Kako. During that flight, he searched for the accident pilot's airplane but could not locate the airplane. After landing at Kako, the interviewed pilot notified the Federal Aviation Administration (FAA) Flight Service Station about the overdue airplane, and the FAA issued an alert notice (ALNOT) at 1748. On October 17, the accident airplane was located submerged in the Yukon River about 10 miles southwest of Russian Mission.

The interviewed pilot stated that he flew his airplane at 1,500 ft agl above the fog and with 20-mile visibility. The pilot also stated that, at that altitude, he could see fog laying on the ground, on hills, and over the Yukon River. He did not know the altitude of the accident airplane but indicated that, in the area of the accident site, the fog was thick with no holes visible.

The pilot, age 31, held a private pilot certificate with an airplane single-engine land rating. The pilot did not have an instrument rating. His most recent third-class medical certificate was issued on February 1, 2014, without waivers or limitations. At the time of the pilot's application for his medical certificate, he reported 35 hours of total flight experience. A relative of the pilot estimated that he had accumulated about 160 hours of total flight experience.

The airplane was manufactured in 1963 and was equipped with a Continental Motors IO-470 series engine. The airplane's last annual inspection was completed on September 8, 2017. At that time, the airplane had accumulated 5,533.7 total hours, and the tachometer displayed 1,649.2 hours.

The National Transportation Safety Board (NTSB) performed a detailed weather study for this accident. Russian Mission Airport, located about 9 nautical miles (nm) north-northeast of the accident site, was the closest airport with official weather observations. At 1413 (about 17 minutes before the accident), a METAR reported the following information: wind from 140° at 3 knots; visibility 10 statute miles; scattered clouds at 300 ft agl, scattered clouds at 2,600 ft agl, and broken ceiling at 3,600 ft agl; temperature 37°F; dew point 36°F; and altimeter setting 29.68 inches of mercury. At 1446 (about 16 minutes after the accident), a METAR reported the following information: wind from 170° at 4 knots; visibility 10 statute miles with light rain; scattered clouds at 1,000 ft agl, broken ceiling at 2,300 ft agl, and overcast skies at 3,400 ft; temperature 37°F; dew point 34°F; and altimeter setting 29.68 inches of mercury. In addition, the 1446 METAR reported that the rain began at the airport at 1432.

Marshall Don Hunter Sr. Airport, Marshall, Alaska, the next closest airport with official weather observations, was located 21 nm northwest of the accident site. At 1356 (34 minutes before the accident), a METAR reported wind from 250° at 4 knots, visibility 10 statute miles, broken ceiling at 2,700 ft agl and overcast skies at 3,500 ft agl, temperature 37°F, dew point 35°F, and altimeter setting 29.67 inches of mercury.

Only one pilot report (PIREP) was available for the 3 hours surrounding the accident at an altitude below 18,000 ft and within 200 nm of the accident site. The PIREP was reported over Aniak, Alaska (about 50 nm southeast of the accident site), at 1512. The pilot of a Cessna 208 reported an overcast ceiling at 700 ft with cloud tops at 4,000 ft.

The area forecast issued at 1206, which was valid at the time of the accident, forecasted an AIRMET for instrument conditions, broken to overcast ceiling at 300 ft with cloud tops at 10,000 ft, and visibilities below 1 mile in mist with improving conditions forecast into the afternoon and evening hours.

The closest National Weather Service Weather Surveillance Radar-1988, Doppler (WSR-88D) was near PABE, located 52 miles south-southwest of the accident site. The radar detected reflectivity targets and associated rain showers above the accident site at 1422 and 1432. The area of rain showers was moving from southwest to northeast and had moved over and past the accident site between 1402 and 1442. No lightning strikes were at or near the accident site at the accident time.

The FAA's aviation weather cameras in Russian Mission showed the weather conditions surrounding the time of the accident. Images from the south- and southwest-facing cameras depicted rain shower conditions with the rain showers moving across the area with low ceiling and visibility conditions within the rain showers beyond the visibility reference point. The south-facing camera also indicated a low bank of clouds toward the Yukon River, the accident site, and along the intended flight route.

The airplane was manufactured in 1963 and was equipped with a Continental Motors IO-470 series engine. The airplane's last annual inspection was completed on September 8, 2017. At that time, the airplane had accumulated 5,533.7 total hours, and the tachometer displayed 1,649.2 hours.

The airplane was located about 10 miles southwest of Russian Mission, submerged about 15 ft in the Yukon River. The main wreckage was recovered and moved ashore. A portion of the forward fuselage, the engine, and the wings were located but could not be recovered. The location of these parts items has been confirmed using SONAR equipment and will be examined if they are eventually recovered at a later date.

The horizontal and vertical stabilizers remained attached to the empennage. The vertical stabilizer and left horizontal stabilizer were relatively free of impact damage. About 3 ft of the outboard portion of the right horizontal stabilizer and elevator was displaced about 45° up and was absent any leading-edge nicks or gouges.

The aft fuselage separated from the forward fuselage at the upper production joint near the forward end of the rear windows. The rivets from the upper production joint on the left side were pulled through the joint, which was consistent with the left wing rotating forward during impact. The rivets from the upper production joint on the right side did not pull but were popped out, which was consistent with the right wing rotating aft during impact.

The front left (pilot) seat was located about 5 miles downstream from the main wreckage location. The seat did not show any evidence of compression damage. The front right (copilot) seat was located about 10 miles downstream from the main wreckage location. Compression damage appeared on the bottom of the seat on the right side. More compression was found on the forward right side of the seat than on the rear right side. The left side of the seat showed relatively little crushing damage.

An FAA safety brochure, titled "Spatial Disorientation Visual Illusions," included the following information:

The flight attitude of an airplane is generally determined by the pilot's visual reference to the natural horizon. When the natural horizon is obscured, attitude can sometimes be maintained by visual reference to the surface below. If neither horizon nor surface visual references exist, the airplane's attitude can only be determined by artificial means such as an attitude indicator or other flight instruments. Surface references or the natural horizon may at times become obscured by smoke, fog, smog, haze, dust, ice particles, or other phenomena, although visibility may be above VFR minimums. This is especially true at airports located adjacent to large bodies of water or sparsely populated areas, where few, if any, surface references are available. Lack of horizon or surface reference is common on over-water flights, at night, or in low visibility conditions.

To prevent spatial disorientation, the brochure recommended relying on flight instruments when flying in reduced visibility conditions and not attempting visual flight when there is a possibility of being trapped in deteriorating conditions.

The State of Alaska Medical Examiner's Office, Anchorage, Alaska, conducted an autopsy of the pilot. His cause of death was multiple blunt force injuries.

The FAA's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicology testing on specimens from the pilot, which were negative for drugs, ethanol, and carbon monoxide.

The airplane was equipped with a J.P. Instruments (JPI) Engine Data Monitor (EDM) model 730, installed under STC SA00432SE and STC SA2586NM. The EDM model 730 is a panel-mounted LCD display that can monitor and record up to 24 parameters related to engine operations, including cylinder head temperature for each cylinder, exhaust gas temperature for each cylinder, fuel flow, fuel pressure, RPM, manifold pressure, and oil pressure and temperature.

The EDM was removed from the accident airplane and sent to the NTSB's Vehicle Recorders Laboratory in Washington, DC, for download. The data began recording at 1418:42 and were recorded in 6-second intervals. At 1420:30 and 1421:30, the engine parameters appeared consistent with the engine run-up. The manifold pressure, rpm, and other engine parameters appeared consistent with the takeoff roll at 1421:40.

For about the next 9.5 minutes, until the data recording ended at 1431:06, all engine parameters appeared nominal. Specifically, the final set of recorded data indicated that the cylinder head temperatures ranged from 290° to 365° F, exhaust gas temperatures ranged from 1,404° to 1,503° F, fuel flow was 13.1 gallons per hour, rpm was 2,415, manifold pressure was 23.4 inches of mercury, oil pressure was 39 psi, and oil temperature was 123° F. The EDM specialist's factual report is in the public docket for this accident.

The attitude indicator was also removed from the airplane and was examined by the NTSB Materials Laboratory in Washington, DC. The indicator's glass face was intact with slight scratching damage. No significant deformation damage was found on the outside of the case. After disassembly, the gimbals were found to move freely. Further disassembly to the gyro revealed wetness and corrosion, but the rotor spun freely on the shaft within its housing. No scoring or deep gouge marks were observed in either the rotor or gyro housing surfaces.