History of Flight
On September 10, 2016, about 1630 Alaska daylight time, a float-equipped, experimental amateur-built Hefty Polar Cub airplane, N62905, was destroyed following a loss of control and subsequent impact with tree-covered terrain in a residential neighborhood in Anchorage, Alaska. The private pilot, the sole occupant, was fatally injured. The airplane was registered to and operated by the pilot as a personal local flight under 14 CFR Part 91. Visual meteorological conditions prevailed, and no flight plan was filed. The flight reportedly originated from Jewell Lake in southwest Anchorage about 1500, but the actual departure time and flight route are unknown.
According to family and friends, the purpose of the flight was to fly over a proposed hunting site near Willow, Alaska, and then return to Anchorage. The friend related that the pilot and a group of friends were planning a fly-in hunt later in the week.
Multiple witnesses consistently reported that they observed the airplane complete two low-level, high-speed, 360° right turns over a residential neighborhood. The first 360° turn was at an altitude between 150 and 200 ft above ground level, and the second turn was much lower. One homeowner stated the airplane passed about 50 ft above his roofline. Witnesses reported that the bank angle increased significantly on the second turn; one pilot-rated witness estimated a bank angle in excess of 60°. Multiple witnesses heard the engine operating at high power settings throughout both turns.
As the airplane completed the second steep turn, the nose pitched down, and it began a rapid nose-down descent. Engine rpm increased significantly, and the wings rolled level just before impact with a stand of tall trees adjacent to a home. During the collision, the floats were severed, and the airplane descended onto a neighborhood road, coming to rest inverted. A postimpact fire ensued about 30 seconds later, engulfing the entire airplane.
A family member and a friend reported that the pilot's flying as described was highly unusual and uncharacteristic.
Pilot Information
The pilot, age 75, held a private pilot certificate with an airplane single-engine land rating; he did not hold a single-engine sea rating. He also held an FAA repairman certificate for the accident airplane. His most recent third-class medical certificate, issued May 23, 2007, contained the limitation: "Not valid for any class after May 31, 2008." On the application, he indicated about 2,200 flight hours. No personal flight records were located.
Aircraft Information
The airplane, resembling a Piper PA-11, had a rectangular, welded steel-tube structure covered with fabric. At the time of the accident, it was equipped with EDO 2000-series floats. The airplane was built by the pilot from plans and issued an FAA experimental airworthiness certificate on May 22, 1996, with a Continental Motors C-90-12-F engine. At the time of the accident, it was equipped with a Lycoming O-320-A2A engine and a Catto composite propeller; no installation documentation was located. No maintenance records were found; family members indicated the logbooks were likely on board. The pilot performed all maintenance.
Meteorological Information
The closest official weather observation station at Ted Stevens Anchorage International Airport, about 10 miles east, reported at 1553: wind 230° at 4 knots, visibility 10 statute miles, few clouds at 2,500 ft, temperature 63°F, dew point 43°F, altimeter 30.14 inHg.
Wreckage and Impact Information
Responding personnel found the inverted and burning wreckage on a neighborhood road, surrounded by tall trees. All major components were at the main wreckage site, with the longitudinal axis oriented on a heading of 035° magnetic. Flight control continuity was established.
The first impact point was a stand of tall spruce trees about 120 ft from the wreckage point of rest, with broken branches and fabric in the treetops. The second impact point was another stand of trees about 100 ft from the point of rest, where the two floats were found entangled. The right wing was displaced aft, fabric burned away; the left wing was displaced aft about 45°, most fabric burned. The entire cockpit and fuselage were consumed by fire. The propeller hub remained connected to the crankshaft, but blades were obliterated. The engine had impact and fire damage; drive train continuity was established; spark plugs were dry with no unusual signatures.
Medical and Pathological Information
A postmortem examination attributed the cause of death to blunt force injuries, with extensive lacerations of the aorta, heart, and liver. There was no soot in the tracheobronchial tree. Toxicological examinations revealed 48% carboxyhemoglobin (carbon monoxide) in the pilot's blood. Additionally, amlodipine, metoprolol, naproxen, and rosuvastatin were detected; none of these medications adversely affect performance. The pilot had a history of hypertension, high cholesterol, coronary artery disease, and bladder neck obstruction.
Tests and Research
On December 2, 2016, after notification of elevated carboxyhemoglobin, the NTSB IIC recovered the accident airplane's exhaust system. The muffler can assembly was severely degraded and damaged, with cracks around most of its circumference near the inlet. The muffler can material was missing in portions, with white, oxidized exhaust deposits. Cracks and corrosion were seen on the interior surface of the exterior shroud under a riveted doubler.