History of Flight
On November 4, 2017, at 1728 central daylight time, a Beech V35B Bonanza, registered N777PH, was destroyed after impacting terrain during approach to Alva Regional Airport (AVK) in Alva, Oklahoma. The flight was a local instructional flight under 14 CFR Part 91, departing AVK at about 1710. Day visual meteorological conditions prevailed, and no flight plan was filed. According to a state trooper who spoke with the pilot at an emergency room, the pilot and flight instructor had flown to Cherokee Municipal Airport for a practice approach and were returning to AVK when the accident occurred. The pilot reported that the left engine cowling had opened during the approach, and the flight instructor subsequently took control. About half a mile before the runway 18 threshold, the airplane collided with trees and a power line approximately 40 ft higher than the airport elevation. The airplane came to rest inverted on its left side, and a postcrash fire ensued. Both occupants egressed with their clothing on fire. The flight instructor was unable to escape the wreckage and died at the scene. The pilot climbed a nearby hill, where responders helped extinguish his burning clothes. He was taken to a local emergency room and later transported to the Integris Burn Center in Oklahoma City with burns over more than 80% of his body; he died on November 7, 2017, from his injuries.
Personnel Information
The flight instructor, aged 61, held commercial pilot and flight instructor certificates with single- and multiengine land and instrument ratings. His most recent FAA medical application from May 15, 2017, reported 2,529 hours of civil flight experience, with 110 hours in the previous six months. An insurance application from May 1, 2017, listed 11,456 total flight hours, including military experience. He owned a Beech Bonanza and frequently trained in the type. The pilot, aged 39, held a private pilot certificate with a single-engine land rating and a third-class medical certificate issued September 10, 2014. His logbook showed 231 flight hours as of June 1, 2017. He had recently purchased the accident airplane and selected the flight instructor based on his reputation with Bonanza training. The accident occurred during the pilot's first training flight and second overall flight in the airplane.
Aircraft Information
The airplane, serial number D-9544, received its standard airworthiness certificate on October 17, 1973. It was powered by a Continental IO-520-BA10 engine and a three-bladed McCauley propeller. A second control yoke was installed before the accident flight. The last annual inspection occurred on May 1, 2017, at a total airframe time of 1,927.7 hours. In 1979, a Robertson Short Takeoff and Landing (STOL) system was installed per Supplemental Type Certificate SA503NW, modifying the flaps and roll control. A handwritten list of airplane discrepancies found in the pilot's hangar included "cowling latch - pilot's side rear spring." The cowling latch mechanism consists of two springs per latch. The airplane flight manual describes the latch operation and checking procedure. Beechcraft released a Safety Communique in 1995 advising pilots to ensure proper latching and maintain control.
Wreckage and Impact
Evidence indicated the airplane struck a tree and a power line before coming to rest inverted in a shallow wash near a hill. Most of the fuselage and right wing were consumed by fire; several trees were burned. Flight control cables were continuous but had separated from controls due to melted structure. The left-wing flap was found extended 30°, and the landing gear was extended. Two control yokes were recovered. The engine exhibited thermal damage, but examination found no pre-impact mechanical anomalies. Three of the four engine cowling latches and three bayonet fittings were recovered; none of the latches were engaged by a bayonet fitting. The exterior cowling handles were in the latched position.
Medical and Pathological Information
Autopsies were performed by the Oklahoma Office of the Chief Medical Examiner. The flight instructor's death was attributed to smoke inhalation and thermal burns; toxicology tests were negative. The pilot's death was attributed to thermal injuries; toxicology detected therapeutic levels of morphine consistent with emergency medical treatment.
Additional Tests
An article from the American Bonanza Society described handling characteristics of STOL-converted Bonanzas, noting pronounced pitch-down forces with full flap extension. A post-accident flight in a similar STOL airplane revealed that extending flaps from 15° to 30° without trim adjustment caused a pitch-down of about 20° and a vertical airspeed increase exceeding 1,500 ft per minute in approximately five seconds.