ANC13FA093

The pilot departed a remote, off-airport site to search for a moose he had shot earlier in the day. A witness observed the airplane perform a series of low-altitude maneuvers before flying by his location about 80 to 100 feet above the ground. The airplane then began a left turn, and the nose of the airplane pitched down abruptly and began to spin. The airplane subsequently descended vertically, nose first, and it collided with the tundra and brush-covered terrain. A postaccident examination of the airframe and engine revealed no mechanical malfunctions or anomalies that would have precluded normal operation. Given the lack of mechanical deficiencies with the airplane and engine, the witness statements, and the nature of the damage to the airplane, it is likely that the pilot inadvertently stalled and spun the airplane at a low altitude and was unable to recover.

The airplane was a 1952 model year, Cessna 170B airplane. At the time of the accident the airplane had a total time in service of 3,307.3 flight hours. A review of the maintenance records revealed that the most recent annual inspection of the airframe and engine was on July 12, 2013, 6.1 flight hours before the accident. The airplane was equipped with a Continental Motors C145 engine, rated at 145 horsepower at 2,700 RPM. The engine was overhauled 395.3 hours before the accident. On September 5, 2013, about 1954 Alaska daylight time, a Cessna 170B airplane, N170BN, sustained substantial damage following a loss of control and a subsequent impact with tundra-covered terrain, about 74 miles northwest of Glennallen, Alaska. The airplane was being operated by the pilot as a visual flight rules (VFR) personal flight under the provisions of Title 14, CFR Part 91, when the accident occurred. The private pilot, the sole occupant, was fatally injured. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight departed from a remote mountain ridge near the accident site. According to a member of the pilot's hunting party, the pilot had shot and killed a moose earlier in the day in an area of tall brush and tundra-covered terrain, but he failed to mark its location before hiking away from the site. Unable to locate the dead moose amongst the tall brush, he hiked back to the airplane that was parked atop a mountain ridgeline, and then he departed to do an aerial search for the moose kill site. According to a witness, after the airplane departed from the mountain ridgeline he watched the airplane do a series of low altitude maneuvers as the pilot began his search. The witness said that he observed the airplane fly by his location at approximately 80 to 100 feet above the ground, traveling at an estimated 45 mph. He said that after it passed by it then began a left turn, and then the nose of the airplane pitched down abruptly and it began to spin. The airplane subsequently descended vertically, nose first, and it collided with the tundra and brush-covered terrain. A post mortem examination was conducted under the authority of the Alaska State Medical Examiner, Anchorage, Alaska, on September 9, 2013. The cause of death for the pilot was attributed to multiple blunt force injuries. The Federal Aviation Administration (FAA) Civil Aeromedical Institute performed toxicology examinations for the pilot on October 16, 2013, which was negative for carbon monoxide, alcohol and drugs. The closest weather reporting facility is Eureka Lodge, approximately 38 miles southeast of the accident site. At 1956, an aviation routine weather report (METAR) at Eureka Lodge, Alaska, reported, in part: wind 230 degrees at 8 knots, visibility, 10 statute miles, clouds and sky condition, clear; 46 degrees F; dew point 35 degrees F; altimeter, 29.96 inHG. The pilot, age 41, held a private pilot certificate with an airplane single-engine land rating. Hismost recent third-class medical was issued on June 10, 2011, with the limitation that he must wear corrective lenses. No personal flight records were located for the pilot, and the aeronautical experience listed on page 3 of this report was obtained from a review of the airmen Federal Aviation Administration (FAA) records on file in the Airman and Medical Records Center located in Oklahoma City. On the pilot's application for medical certificate, dated June 13, 2011, he indicated that his total aeronautical experience was about 186 hours, of which 12 were in the previous 6 months. Continuous poor weather conditions in the area prevented the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), and a representative from Cessna Aircraft Company from reaching the accident site until the afternoon of September 8. The on-scene examination revealed that the airplane impacted in a near vertical attitude, in an area of brush and tundra covered terrain, at an elevation of about 3,750 feet mean sea level. The nose of the airplane was on an approximate 060 degree heading (All headings/ bearings noted in this report are magnetic). All of the airplanes major components were found at the main wreckage site. The cockpit area was extensively damaged. The engine, firewall, and instrument panel were displaced upward and aft. The mixture control was found in the full-forward position, and the throttle near the idle stop. The carburetor heat was in the off position. The ignition switch was in the "both" position. The airplane's right wing remained attached to the fuselage, and the entire leading edge exhibited extensive spanwise leading edge aft crushing. The lift strut remained attached to its attach points, and was free of impact damage. The airplane's left wing remained attached to the fuselage, and exhibited leading edge aft crushing from the wing root to about mid-span. The lift strut remained attached to its attach points, and was free of impact damage. Both left and right flaps remained attached to their respective attach points. The inboard portion of the right flap was crushed against the side of the fuselage approximately 20 degrees down. The left flap was relatively free of impact damage. Both left and right flap rollers appeared to be approximately 20 degrees. The horizontal and vertical stabilizer, elevators, and rudder remained attached to the empennage, and were free of impact damage. All the primary flight control surfaces remained connected to their respective attach points, and flight control continuity was verified from all of the primary flight control surfaces to the cockpit. Numerous pieces of cut brush were present at the initial impact site, and on both the left and right side of the wreckage forward of the engine. Examination of the brush revealed flat angular fractures with black paint transfer marks. The engine sustained impact damage. The propeller remained attached to the engine crankshaft. One propeller bladeexhibited substantial torsional "S" twisting and chordwise scratching. The other propeller blade exhibited leading edge gouging. The examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.