Antioch, CA, USA
N644LL
Yakovlev YAK 52
A witness located north east of the accident site, observed the airplane "starting a vertical climb, slowly rolling over and diving straight down." The witness stated that the airplane "never appeared to be trying to pull out of the dive." Subsequently, the witness lost sight of the airplane behind a mountain, and heard the "sound of impact." Examination of the wreckage revealed a screwdriver located in the aft section of the fuselage. Multiple witness marks were observed around the elevator bellcrank housing, and numerous gouges on the screwdriver. When the screwdriver was placed between the elevator bellcrank and housing, and the bellcrank moved by hand, the elevator control was restricted to the neutral position. The energy dispersive x-ray spectroscopy analysis performed on the screwdriver conclusively demonstrated that the screwdriver was lodged between the various structural items.
HISTORY OF FLIGHT On June 18, 2002, at 1220 pacific daylight time, a Yakovlev Yak 52 single-engine aerobatic airplane, N644LL, was destroyed when it impacted terrain following a loss of control while maneuvering near Antioch, California. The airplane was registered to a private individual and operated by another private individual. The commercial pilot, sole occupant of the airplane, was fatally injured. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 personal flight. The local flight originated from the Livermore Municipal Airport, near Livermore, California, at 1005, and was destined for the Buchanan Field (CCR), near Concord, California. A witness, located northeast of the accident site, observed the airplane "starting a vertical climb, slowly rolling over and diving straight down." The witness stated the airplane "never appeared to be trying to pull out of the dive." Subsequently, the witness lost sight of the airplane behind a mountain and heard the "sound of impact." PERSONNEL INFORMATION The pilot held an airline transport pilot certificate with an airplane multi-engine land rating, a commercial pilot certificate with an airplane single-engine land rating, and instrument airplane ratings. He also held a flight instructor certificate with an airplane single-engine land, airplane multi-engine land and instrument airplane ratings, issued on December 6th, 1999. The pilot received a type rating in the Beech BE-300 aircraft on November 16, 2000. Review of the pilot's logbooks revealed that the pilot had accumulated a total of 2,688.1 hours of flight time, of which 21.3 hours were in the last 90 calendar days prior to the date of the accident. The pilot had accumulated a total of 41.8 hours in the accident make/model aircraft, 11.1 of which were within the last 30 days prior to the accident. The pilot was issued a first class medical certificate on August 1, 2000, with a limitation requiring that the holder to wear corrective lenses. AIRCRAFT INFORMATION The Yak 52 airplane was a tandem seat, fully aerobatic aircraft, capable of G loading limits from +7g to -5g. The Russian-built primary trainer was manufactured in May of 1983. The airplane was powered by a 360-horsepower nine-cylinder Ivchenko M-14P radial engine, driving a two-bladed counter-clockwise rotating, constant speed wooden propeller. Information provided by the owner of the airplane revealed that the airplane was imported to the United States from Lithuania in June of 2000. Review of the aircraft and engine logbooks revealed the airframe, engine, and propeller underwent their most recent annual inspection on July 15, 2001, accumulating a total of 1,144.6 hours total time. The engine accumulated 140.2 hours since major overhaul that was performed by the factory in Lithuania on January, 23, 2000. The flight controls on the Yak-52 may be operated from either the front or rear seat; however, the pilot in command typically occupies the front seat. Elevator control was obtained by a push rod that links the forward and aft control sticks and are connected to a bellcrank assembly below the rear seat. Cables connected to the bellcrank assembly ran through the aft fuselage to an elevator bellcrank that has the elevator counterweights attached, and was connected to the elevator control surfaces. To achieve full nose-up elevator, the bellcrank and counterweight passed through an opening in the fuselage into the vertical stabilizer. The fuselage of the Yak-52 was open from the forward firewall aft to the tail section that houses the bellcrank assembly. There are no bulkheads, or barriers to restrict foreign objects from traveling throughout the fuselage of the airplane. Inspection of the aft section of the empennage is obtained from the rear seat in the cabin, but is limited by an electrical equipment rack that is located just aft of the rear seat. An inspection panel is located under the left horizontal stabilizer that allows for inspection of the aft section of the fuselage. WRECKAGE AND IMPACT INFORMATION The wreckage was located on the 105-degree radial of the CCR VHF Omni-directional Range (VOR) at 15 nautical miles. A Federal Aviation Administration (FAA) inspector, who responded to the accident site, reported the airplane came to rest inverted in a shallow crater within a hard surfaced rural field. All flight control surfaces were accounted for at the accident site, and control continuity was established from cockpit controls aft to the empennage. The wreckage debris distribution area remained within a 30-foot radius of the main wreckage. Both wings were crushed aft, and the engine was crushed aft into the cabin area. The airplane exhibited signs of a near vertical impact. Cockpit instrumentation was not documented due to the extent of the damage. On July 9, 2003, at the facilities of Plain Parts, near Pleasant Grove, California, the NTSB examined the wreckage and discovered a red and clear plastic flat-bladed screwdriver that was located in the aft section of the fuselage. The screwdriver was approximately six inches in length, four inches round, and exhibited numerous gouge and scrape marks. A green substance was found deep within some of the gouges. On August 4, 2003, the NTSB further examined the tail section of the airplane. Several witness marks were found around the elevator bellcrank and counterweight housing area. A red substance was found on the end of the lower elevator bellcrank cable. The bellcrank housing area, bellcrank, and screwdriver were sent to the NTSB materials laboratory in Washington, DC, for further examination. Examination of the screwdriver, bellcrank, and bellcrank housing was conducted in the NTSB Office of Research and Engineering, Materials Laboratory Division on August 20, 2003. The screwdriver, bellcrank, and bellcrank housing were examined using energy dispersive x-ray spectroscopy (EDS) to qualitatively determine the chemical composition of the green substance located within the damage on the screwdriver handle, the clear area on the screw driver handle away from areas of damage, and the red material on the end of the lower bellcrank cable. The EDS spectra for the green substance located within the damage on the screwdriver handle had a high peak of silicon with smaller peaks of carbon, magnesium, aluminum, sulfur, chlorine, potassium, calcium, titanium, chromium, iron, and zinc. The clear areas away from the damage had a high peak of carbon with lower peaks of oxygen and silicon. Samples of paint from the bellcrank housing, including the inner green layers and an outer white layer, were removed. The inner (green) side was examined and the resulting spectrum had high peaks of zinc and carbon with smaller peaks of oxygen, magnesium, aluminum, silicon, sulfur, chlorine, potassium, titanium, and chromium. The EDS spectra for the red material on the cable end for the lower cable had a high peak of silicon with smaller peaks of carbon, oxygen, zinc, magnesium, aluminum, sulfur, chlorine, potassium, calcium, iron, and zinc. The EDS spectrum for the cable material showed a high peak of iron with smaller peaks of carbon, oxygen, and zinc. The EDA spectrum showed a high peak of carbon and smaller peaks of oxygen, aluminum, silicon, and potassium. When the screwdriver was placed between the elevator bellcrank and housing, and the bellcrank moved by hand, full up elevator control was restricted to the neutral position. METEOROLOGICAL INFORMATION At 1253, the automated surface observing system at CCR reported wind from 280-degrees at 9 knots, visibility 10 statute miles, sky conditions clear, temperature 91 degrees Fahrenheit, dew point 48 degrees Fahrenheit, and an altimeter setting of 29.83 inches of Mercury. MEDICAL AND PATHOLOGICAL An autopsy was performed on the pilot on Jun 24, 2002, by the Forensic Services Division, of Contra Costa Country, State of California. No evidence was found of any preexisting disease that could have contributed to the accident A toxicology test was performed by the Federal Aviation Administration's Civil Aeromedical Institute (CAMI) in Oklahoma City, Oklahoma, for volatiles, and drugs. Carbon Monoxide and Cyanide tests were not performed. The toxicology test revealed that an unspecified amount of Quinine was detected in the heart and kidney. TESTS AND RESEARCH Several YAK 52 accidents have been reported around the world. An accident occurred in Smolensk, Union of Soviet Socialists Republic (U.S.S.R.), in 1998. Information obtained from the Skytrace website (http://www.skytrace.co.uk/), the pilot was participating in an aerobatic performance. After "two vertical figures the aircraft control was partly jammed." The aircraft "made a slow right roll and started to descend from a height of 300-400 meters (984-1300 feet). It increased the descending angle and came into collision with the ground at a diving angle of 80 degrees." The pilot sustained fatal injuries. An investigation revealed a camera lens cap that had been lost by a cameraman on a previous flight became "jammed in the fastening lever of the elevator-balancing load." According to a United Kingdom YAK importer-distributor (whose company provides YAK 52 flight training and maintenance), there were two similar, but nonfatal, accidents in Lithuania in 2002 (http://www.yakuk.com). The first occurred in Kaunas. The pilot was forced to parachute to safety when a flight recorder frame (the recorder had been removed) jammed the elevator controls. In the second, the pilot rolled inverted and discovered the elevator control was inoperable. He rolled the airplane upright and the elevator control worked freely. The item that caused the control to jam was not given. According to the owner of AirCare Systems, a YAK 52 importer-distributor in Lamar, Colorado, there was an incident in Atlanta, Georgia (date not given). A YAK 52 pilot was doing aerobatics when a radio knob came off and "jammed the elevator control." He managed to land without incident. In addition, the AirCare Systems owner stated that during a recent preflight of his personal YAK 52, he removed the inspection panels and found a checklist and radio knob in the bellcrank housing area that he had lost several months previously. On January 16, 2003, a YAK 52, near Midway, Utah, was observed by witnesses in a vertical or near-vertical attitude just prior to impact, and the engine sounded like it was developing full power. None of the witnesses reported seeing the airplane performing aerobatic maneuvers. Examination of the airplane by the NTSB revealed a brass nut, found in the crushed skin of the empennage. The nut exhibited numerous gouge marks. The nut was placed between the elevator bellcrank and housing. When the bellcrank was moved by hand, full up and down elevator control could not be achieved due to the impeding nut. The gouges on the nut were consistent with elevator bellcrank contact. Scrape marks were also noted on the underside of the bellcrank housing. Another accident occurred in Northamptonshire, England, near Towcester, on January 5, 2003. According to the Department for Transport's website (http://www.dft.gov.uk/), after a series of aerobatic maneuvers, the aircraft completed a stall turn and entered a vertical dive from which it did not recover. Both pilot and passenger were fatally injured. Examination of the wreckage revealed the presence of a short-handled flat bladed screwdriver that had jammed the elevator control such that the elevator control surface could not be moved beyond neutral in the nose-up direction. An article in the September 2003, issue of Aircraft Owners and Pilots Association (AOPA) Magazine, under the "Never Again" section, featured information about a Yak 52 performing aerobatics approximately 2,700 feet agl. Upon exiting a "Cuban eight" maneuver, and recovering from a dive, the pilot "started the pull out, but the stick was frozen." At approximately 300 feet agl, the pilot was able to level the aircraft off and access the situation. The pilot requested help from the passenger, a non-pilot, in the rear seat to help "maintain backpressure" on the controls. After landing at a nearby airport, the pilot examined the aft part of the fuselage and elevator. The pilot stated he pushed up on the elevator and it would not travel past neutral. When he pulled the elevator down, it traveled all the way and he heard a "metallic plunk." The pilot removed the inspection panel on the left side of the fuselage under the horizontal stabilizer, and found a seven-inch vice grip tool. After a brief investigation by the pilot, it was discovered that the tool was left in the airplane two months prior when the last maintenance was conducted. ADDITIONAL INFORMATION The wreckage was released to an owner's representative on July 28, 2003.
The loss of control while performing acrobatic maneuvers due to a screwdriver restricting elevator travel. A contributing factor was the airplane's fuselage not being sterile of foreign objects.
Source: NTSB Aviation Accident Database
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