Ava, MO, USA
N4712Z
Piper PA-22-108
The passenger reported that during cruise flight the airplane inexplicably began a shallow left turn that the pilot was unable to counteract. The pilot reportedly moved the yoke to the left and right without any effect on the left bank angle. The airplane continued the unintended left turn with an increasingly steeper bank angle for three complete turns. The passenger reported that the airplane's pitch was vertically nose-down at the completion of the third turn, at which time the airplane impacted trees and terrain. The aileron control cable circuit was examined during the investigation. The inboard end of the right aileron upper cable was missing its eye splice and thimble. The cable had an approximate 90 degree bend at the location corresponding to the eye, consistent with residual deformation associated with an eye loop. The cable separation did not exhibit any kinking or heavy rubbing. The remaining sleeve (nicropress) on the right aileron upper cable did not conform to the manufacturer's specified crimp dimensions and had tooling markings that were not consistent with the use of the specified installation tool. In a properly installed eye splice, the cable should fracture before pulling out of its corresponding sleeve. The aileron cables used had a specified limit load of 2,000 pounds. The remaining eye splice on the right aileron upper cable pulled out of its sleeve at 476 pounds. The other five eye splices tested held more than 1,600 pounds before failure occurred in the cable. A review of the aircraft's maintenance logbooks did not reveal any specific mention of aileron control cable replacement. However, given the variability in the appearance and characteristics of the other aileron cable sleeves, it is likely that the nonconforming sleeves were not of original manufacture.
HISTORY OF FLIGHT On April 16, 2007, at approximately 1600 central daylight time, a Piper PA-22-108 (Colt), N4712Z, owned and piloted by a private pilot, was substantially damaged during impact with trees and terrain following a loss of control during cruise flight near Ava, Missouri. Visual meteorological conditions prevailed at the time of the accident. The flight was operating under the provisions of 14 Code of Federal Regulations Part 91 without a flight plan. The pilot was fatally injured and his passenger sustained minor injuries. The flight departed Gastons Airport (3M0), Lakeview, Arkansas, at an unknown time, and was en route to Mountain Grove Memorial Airport (1MO), Mountain Grove, Missouri. The passenger reported that during level cruise flight at 3,000 feet mean sea level the airplane inexplicably began a shallow left turn that the pilot was unable to counteract. The pilot reportedly moved the yoke to the left and right without any effect on the left bank angle. The airplane continued the unintended left turn with an increasingly steeper bank angle for three complete turns. The passenger reported that the airplane's pitch was vertically nose-down at the completion of the third turn, at which time the airplane impacted trees and terrain. PERSONNEL INFORMATION According to Federal Aviation Administration records, the pilot, age 64, held a private pilot certificate with a single engine land airplane rating. His last aviation medical examination was completed on December 27, 2005, when he was issued a third-class medical certificate with the limitation "holder shall possess glasses for near & intermediate vision." The pilot's most recent logbook entry was dated February 27, 2007, at which time he had accumulated 690 hours total flight time. He had accumulated 24 hours at night, and 5 hours in actual instrument conditions. His last flight review was completed on March 14, 2006. AIRCRAFT INFORMATION The accident airplane was a single engine 1961 Piper PA-22-108 (Colt), serial number 22-8256. The airplane incorporated a strutted high-wing design with a fixed tricycle landing gear, and could accommodate two occupants. The airplane was powered by a Lycoming O-235-C1B four- cylinder, carbureted, reciprocating engine. The 108-horsepower engine provided power through a Sensenich M76AM-2 two-bladed propeller. The metal propeller was a fixed-pitch design. According to the maintenance logbooks, the last annual inspection was completed on June 15, 2006, at 2,525 total airframe hours. The engine had accumulated 248 hours since its last overhaul. A review of the airframe, engine and propeller records found no history of unresolved airworthiness issues. METEOROLOGICAL INFORMATION The closest weather reporting facility was at the West Plains Municipal Airport (UNO), about 27 nautical miles east of the accident site. The airport was equipped with an automated surface observing system (ASOS). At 1553, the UNO ASOS reported the following weather conditions: calm winds; visibility 10 statute miles; sky clear; temperature 22 degrees Celsius; dew point 0 degrees Celsius; altimeter setting 30.09 inches of mercury. WRECKAGE AND IMPACT INFORMATION The airplane impacted a deep ravine in a heavily wooded area. Damage to the overhead foliage was limited, consistent with a near vertical descent path. The left wing was separated from the fuselage and was partially suspended in a nearby tree. The right wing remained attached to the fuselage. Both wings exhibited extensive damage consistent with impact. The tail was crushed downward into the main cabin. All primary structural components were recovered within a 10 foot radius of the main impact point. The left fuel tank and left main landing gear wheel were found forward of the wreckage, about 25 feet and 100 feet respectively. The engine remained attached to its engine mounts, but was displaced about 45 degrees right of centerline. The propeller remained attached to the engine. MEDICAL AND PATHOLOGICAL INFORMATION On April 17, 2007, an autopsy was performed on the pilot at the Lester E. Cox Medical Center, Springfield, Missouri. The cause of death was listed as "cervical spine fracture as the result of airplane crash." The FAA's Civil Aeromedical Institute in Oklahoma City, Oklahoma, performed toxicology tests on the pilot. No carbon monoxide or cyanide was detected in blood, no ethanol was detected in vitreous, and no drugs were detected in urine. TESTS AND RESEARCH The aileron control cable circuit was examined at the National Transportation Safety Board's Materials Laboratory in Washington, D.C. The inboard end of the right aileron upper cable was missing its eye splice and thimble. The cable had an approximate 90 degree bend at the location corresponding to the eye, consistent with residual deformation associated with an eye loop. The cable separation did not exhibit any kinking or heavy rubbing. The other crimped sleeves (Nicropresses) in the aileron system were examined and their dimensions measured. Three of the sleeves from the four outboard aileron cables had crimp dimensions consistent with a properly installed sleeve, as specified in the control cable engineering drawings. However, the remaining three sleeves had crimp dimensions that did not conform to manufacturer's specifications. These nonconforming sleeves also had tooling markings that were not consistent with the use of the specified installation tool. One of these nonconforming sleeves was the remaining sleeve on the right aileron upper cable. The strength of the remaining eye splices was tested. In a properly installed eye splice, the cable should fracture before pulling out of its corresponding sleeve. The aileron cables used had a specified limit load of 2,000 pounds. The remaining eye splice on the right aileron upper cable pulled out of its sleeve at 476 pounds. The other five eye splices tested held more than 1,600 pounds before failure occurred in the cable. A review of the aircraft's maintenance logbooks did not reveal any specific mention of aileron control cable replacement.
The failure of the aileron cable eye splice during cruise flight. Contributing to the accident were improper installation and service of the crimped cable sleeve, which rendered the airplane uncontrollable.
Source: NTSB Aviation Accident Database
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