Accident Overview
On August 26, 2010, about 0920 mountain standard time, an experimental amateur-built Finney Thorp T-18, registration N467JF, experienced an in-flight loss of control while entering the downwind leg of the traffic pattern at Cochise County Airport (P33) in Willcox, Arizona. The airplane subsequently descended into terrain, resulting in substantial damage. The private pilot and passenger sustained fatal injuries.
Flight Details
The pilot/owner was operating the airplane under Title 14 Code of Federal Regulations Part 91 for a personal cross-country flight. Visual meteorological conditions prevailed at the time, and no flight plan was filed. The flight originated from San Diego, California, at an undetermined time with an intended destination of Cochise County Airport.
Witness Observations
A witness, a Certified Flight Instructor (CFI) flying approximately 500 feet above the accident airplane in another aircraft, observed the airplane entering the traffic pattern at about 500 feet above ground level (agl). The airplane made a steep left turn to join the downwind leg for runway 03 and subsequently entered a left descending spiral until it impacted the ground in a nose-low attitude. Another witness located at the airport heard the engine power up and saw the airplane initiate a left turn around midfield. Personnel monitoring the airport's common traffic advisory frequency (CTAF) reported hearing an unintelligible distress radio transmission around the time of the accident.
Wreckage Examination
A Federal Aviation Administration (FAA) inspector examined the wreckage at the accident site. The airplane's wings were bent, and the forward portion of the fuselage was crushed aft. No evidence of a preimpact engine malfunction was noted. All flight control surfaces remained attached to their respective mounts except the right flap, which was attached only by the outboard hinge and exhibited impact damage. A separation was found in the left aileron's push-pull control tube, which separated it from the control stick bellcrank.
The left aileron push-pull control tube rod end bearing and jam nut at the separation point were sent to the National Transportation Safety Board (NTSB) Materials laboratory for analysis. A Senior Metallurgist determined through optical examination that the fracture surface was consistent with an overstress load. No indication of progressive cracking or significant corrosion was observed around the fracture surface. The surrounding structure housing the rod end bearing and jam nut was buckled near the separation point.
Medical and Toxicology Information
The Cochise County Office of the Medical Examiner reported that the pilot's cause of death was multiple blunt force injuries. Toxicological samples tested by the FAA Civil Aeromedical Institute were negative for all tested substances.
Aircraft Performance Characteristics
The Pilot Operating Handbook for the T-18 states that the airplane has an abrupt stall with a tendency to drop a wing, especially if uncoordinated during the stall. There is very little warning preceding the stall. Stall recovery can be quickly effected by releasing back pressure on the stick; however, a secondary stall may occur if the stick is brought back after recovery from the initial stall without sufficient airspeed.