In a probable cause report released Wednesday, the National Transportation Safety Board stated a September 2013 fatality aircraft accident involving pilot and sole occupant Michael Zobel was due to pilot error. According to the report, the crash, which took place while Zobel was on a hunting trip about 75 miles northwest of Glennallen, occurred because Zobel failed to "maintain adequate airspeed while maneuvering at a low altitude, which resulted in an aerodynamic stall/spin and impact with the ground".
In his last medical certificate application two years earlier, Anchorage resident Zobel, a private pilot who was the aircraft's sole occupant, estimated he had 186 hours of flight time.
According to a member of his party, Zobel shot and killed a moose earlier that day and failed to mark its location. At about 8 p.m. on Sept. 5, he took off in his Cessna 170B to search for the kill site. In an interview with the NTSB, a witness reported that "he observed the airplane fly by his location at approximately 80 to 100 feet above the ground, traveling at an estimated 45 mph." Shortly thereafter it it began a left turn, pitched down and "began to spin." The aircraft descended nose first into the terrain.
Visual meteorological conditions were present at the time of the accident and weather was not deemed to be a factor.
A survey of the wreckage by investigators determined that it impacted in a near-vertical attitude at about 3,750 feet. The throttle was near the idle stop position, the mixture control at full rich and the flap rollers appeared to be at about 20 degrees. Investigators further reported that "the propeller remained attached to the engine crankshaft. One propeller blade exhibited substantial torsional "S" twisting and chordwise scratching. The other propeller blade exhibited leading edge gouging."
Loss of control at low altitude is a particularly common cause of accidents during hunting season and prompted the NTSB to release a short video by investigator Anchorage Chris Shaver last year. The tendency to fly "low and slow" while searching for moose gives pilots little opportunity for recovery if an aircraft stalls. The best way to avoid an unrecoverable spin at low altitude is prevention, which Shaver stresses in his narration.
Between 2004 and 2012 there were 18 fatal accidents involving loss of control at low altitude in Alaska. These crashes resulted in 27 deaths. As probable cause results from 2013 are released, this number is likely to rise.
Correction: This article originally addressed a separate fatal aircraft accident that took place five days prior to the crash that killed Zobel. We regret the error.
Contact Colleen Mondor at colleen(at)alaskadispatch.com.