Attalla, AL, USA
N5470U
BEECH V35A
The pilot was flying at 9,000 ft mean sea level (msl) on an instrument flight rules flight plan, and likely in turbulent instrument meteorological conditions, when the airplane entered a right descending turn. As the airplane descended through 7,000 ft msl, the controller broadcast the airplane’s call sign and the pilot replied, “yeah im with you im” but the rest of the comment was unintelligible. The airplane continued the right descending turn with the radius of turn becoming smaller until the airplane impacted an open field at a high rate of descent. Postaccident examination determined that the “up” elevator control cable assembly failed after a terminal end in the turnbuckle at the tail of the airplane fractured from fatigue. The presence of fatigue cracking at this location would be consistent with failure of the elevator control cable and subsequent loss of control of the aircraft. The initiation of multiple fatigue cracks was consistent with the roughened surface and pitting due to widespread corrosion. The remnants of cadmium (Cd) found in the iron oxides embedded in the cracks was indicative of a previous Cd coating on the steel surface of the turnbuckle. The Cd was meant to protect the underlying steel from corrosive attack; however, the Cd surface coating had completely deteriorated, leaving the underlying substrates vulnerable. Although an inspection of the airplane, including the flight control cables, was performed as part of an annual inspection about 7 months before the accident, the location of the turnbuckle in the airframe likely would have made it difficult to thoroughly inspect the component while still installed in order to identify wear of the cadmium layer or surface cracks in the part. Given the pilot’s flight and medical history, it is unlikely that his previous amputation or medications contributed to the accident. It is likely that the flight encountered turbulence during the flight. Given the evidence available, it could not be determined if the turbulence or the failure of the turnbuckle was the initiating event of the right descending turn or if the fatigue-weakened turnbuckle failed as the pilot was attempting to recover from the descending turn. After the turnbuckle failed, the pilot’s ability to control the airplane’s pitch would have been significantly diminished and would have made recovery to a nominal flight attitude improbable.
HISTORY OF FLIGHTOn December 12, 2020, about 1249 central standard time, a Beech V35A, N5470U, was destroyed when it was involved in an accident near Attalla, Alabama. The airline transport pilot was fatally injured. The airplane was operated as a Title 14?Code of Federal Regulations Part 91 personal flight. The pilot was flying from Kyle-Oakley Field Airport (CEY), Murray, Kentucky, to Merritt Island Airport (COI), Merritt Island, Florida. According to Federal Aviation Administration (FAA) audio recordings and Automatic Dependent Surveillance-Broadcast (ADS-B) data, the flight departed CEY under visual flight rules about 1131, and shortly after takeoff the pilot contacted Memphis Air Route Traffic Control Center to obtain his instrument flight rules clearance. The flight was radar identified as being 2 miles south of CEY and was cleared to climb to 9,000 ft mean sea level (msl). The flight remained on a southerly heading until about 1133, then turned left to a southeasterly heading. Air traffic control communications were transferred to several air traffic control facilities appropriate for the route of flight as the flight climbed to about 9,000 ft msl. At 1236:35, the pilot established contact with Birmingham Air Traffic Control Tower and the controller issued the current altimeter setting. The flight remained on the southeasterly heading and altitude until 1248:09, when the airplane began a right descending turn that was not directed by the controller or announced by the pilot. At 1248:41, while flying about 7,000 ft msl the controller broadcast the call sign of the airplane and the pilot immediately replied, “yeah im with you im” but the rest of the comment was unintelligible. The airplane completed a 360° right turn and at 1248:47, while flying about 5,500 ft msl, the airplane continued the right descending turn with the radius of turn becoming smaller. The controller broadcast that radar contact was lost but the pilot did not reply. The last ADS-B target at 1248:54 recorded the airplane over a wooded area at about 3,600 ft msl. The airplane impacted an open field about 1,260 ft northeast from the last ADS-B location. Review of ADS-B data revealed that in the minute before the airplane began the right descending turn (between 1247:09 and 1248:09), the airplane travelled about 15,198 ft resulting in a calculated average groundspeed of about 173 mph. The barometric altitude at the last ADS-B target was 3,575 ft, which would have been above the floor of the overcast ceiling. PERSONNEL INFORMATIONThe pilot held a statement of demonstrated ability for his lower left leg that was amputated below the knee following a motorcycle accident in 2004. He reported 13,299 hours total time and 33 hours in the last 6 months as of his last 2nd class medical examination dated December 4, 2018. A review of excerpts of his pilot logbook that begins with an entry dated August 17, 2017, to the last entry dated August 1, 2020, revealed he logged about 109 hours, all of which were in the accident airplane. His last flight review and instrument proficiency check (IPC) were completed on December 7, 2019. Correlating his total flight time reported on his last medical with the logged entries after that date revealed his total time was about 13,340 hours. He did not log any instrument approaches, holding, or navigating after his IPC. Individuals who interacted with the pilot before his departure on the accident flight reported nothing abnormal about their interactions. AIRCRAFT INFORMATIONThe pilot had owned the airplane since September 2010. The airplane was equipped in part with a Garmin G5 and an Apple iPad. Both were retained by the National Transportation Safety Board (NTSB), but no data were able to be obtained from either unit. Before departure, 3.1 gallons of 100LL were added to the left fuel tank which filled it; the right fuel tank was full. According to the airport manager, there were no fuel related issues from any other airplanes fueled from the same fuel source. Prior to departing from CEY, maintenance personnel serviced the nose and main landing gear, and replaced a Dzus fastener for the engine cowling. No other maintenance was performed at CEY. METEOROLOGICAL INFORMATIONThe pilot did not request a flight service weather briefing. A search of archived ForeFlight information indicated that he did request and receive weather information from ForeFlight at 1049. The 1049 weather information contained all the official National Weather Service aviation forecast information for the route of flight. In addition, the pilot requested and viewed other weather imagery at 0809 to 0811on December 12th and viewed additional weather imagery on December 10th and 11th. There is no record of the accident pilot receiving or retrieving any other weather information before or during the accident flight. The complete Rawinsonde Observation Program (RAOB) indicated cloud cover between 1,500 and 11,000 ft msl. The RAOB did indicate the possibility of light to moderate clear air turbulence in several layers between the surface and 14,000 ft msl. At the aircraft’s altitude near 9,000 ft msl around 1248, the wind was from 243° at 50 knots. Based on the brightness temperatures (about 272 Kelvin) above the accident site and the vertical temperature profile provided by the 1300 High-Resolution Rapid Refresh (HRRR) sounding, the approximate cloud-top heights over the accident site were 13,000 ft above msl at 1250. The Huntsville, Alabama weather surveillance radar (WSR-88D) base reflectivity images for the 0.9° elevation scans initiated at 1228:49, 1238:01, 1247:14, and 1251:50, revealed reflectivity values between 5 and 15 dBZ above the accident site at the accident time with the precipitation near the accident site expanding in spatial coverage. There were no convective or non-convective Significant Meteorological Information (SIGMET) advisories valid for the accident site at the accident time. AIRPORT INFORMATIONThe pilot had owned the airplane since September 2010. The airplane was equipped in part with a Garmin G5 and an Apple iPad. Both were retained by the National Transportation Safety Board (NTSB), but no data were able to be obtained from either unit. Before departure, 3.1 gallons of 100LL were added to the left fuel tank which filled it; the right fuel tank was full. According to the airport manager, there were no fuel related issues from any other airplanes fueled from the same fuel source. Prior to departing from CEY, maintenance personnel serviced the nose and main landing gear, and replaced a Dzus fastener for the engine cowling. No other maintenance was performed at CEY. WRECKAGE AND IMPACT INFORMATIONDocumentation of the accident site and wreckage was performed by a representative of Textron Aviation with FAA oversight. According to the FAA inspector, none of the observed items exhibited any evidence of in-flight or postcrash fire. Examination of the accident site revealed wreckage was scattered in an open field for about 535 ft along an energy path of about 100° true. The airplane was heavily fragmented with the largest pieces consisting of sections of the wings, and empennage. The major structural and flight control pieces were identified, and their location documented. The left wing was fragmented in three main pieces while the right wing was fragmented in two pieces. The left flap was retracted as evidenced by the flap actuator while the right flap actuator was not located. No blockage was noted in the pitot tube opening. The flaps and aileron flight control surfaces of both wings were either attached or accounted for. Examination of the wreckage revealed both stabilizers were structurally separated from the empennage and both elevators were separated from each stabilizer. Examination of the flight controls for pitch revealed the cockpit portions of the cables were in multiple pieces and all cable separations exhibited signatures consistent with tension overload. The turnbuckle eye, part number (P/N) AN165-22RL, of the “up” elevator control cable located in the aft portion of the empennage near the control surface and the fork of the “down” elevator control cable in the cockpit were fractured. Examination of the flight controls for roll revealed that the right aileron primary “up” control cable remained attached to the chain in the cockpit and at the bellcrank near the control surface, but the cable terminal was fractured near the turnbuckle outside of the safety wire wrap on the aileron side of the turnbuckle. Further examination of the flight controls for roll and yaw revealed no evidence of preimpact failure or malfunction. Sections of the “up” and “down” elevator control cables and the right aileron primary control cable were retained for examination by the NTSB Materials Laboratory. According to the NTSB Materials Laboratory factual report, the fork of the “down” elevator cable and the terminal end of the right aileron primary control cable exhibited overstress fracture, while the turnbuckle eye of the “up” elevator cable exhibited fatigue on about 15% of the cross section of the surface; the remainder of the fracture surface displayed features consistent with overstress separation. The fatigue crack striations were oriented perpendicular to the longitudinal direction of the surface edge consistent with inward crack growth. The report also indicated that there were multiple parallel cracks on the outside surface of the terminal end. Elevated amounts of sodium, chlorine, and sulfur, consistent with constituents in salts corrosive to steel were noted. In addition, some cadmium was present in the oxide, consistent with the end having been coated with cadmium. A cross section of the cylindrical surface of the terminal end appeared to be rough and uneven, consistent with exposure to corrosive attack. Examination of the left stabilizer revealed it was full span and the inboard portion aft of the main spar was twisted down about 90°. Examination of the fracture surfaces of the forward and aft spars revealed no evidence of preimpact failure or malfunction. The forward spar was twisted. The left elevator was fractured into multiple pieces; the tip was not located. The outboard and middle hinge structure were pulled out of the left elevator and were attached through the hinge point to the left stabilizer, while the torque fitting was structurally separated and not located. The left elevator tab assembly was separated from the elevator but the full span of the elevator tab assembly was accounted for. A section of control cable remained attached the tab assembly. The hinge remained attached to the tab and had evidence of being pulled out of the skin. Examination of the right stabilizer revealed it was full span and compression wrinkles were noted in the upper skin from about midspan inboard. Examination of the fracture surfaces of the forward and aft spars revealed no evidence of preimpact failure or malfunction. The stabilizer forward spar was twisted, and the outboard hinge normally attached to the aft spar was structurally separated. The middle hinge was fractured consistent with overload fracture, and the torque fitting was structurally separated and not located. The right elevator was also fractured into multiple pieces. The right elevator tab assembly was separated from the elevator, but the full span of the elevator tab assembly was accounted for. A section of control cable remained attached the tab assembly. The right elevator tab hinge remained attached to the tab and its rivets had torn through the elevator skin. Examination of the elevators revealed no evidence of overtravel of either elevator in either direction based on examination of the hinges. Further inspection of the four elevator stops revealed no evidence of abnormal contact/impact signatures. The ruddervator trim tab actuator was between 5° and 10° tab trailing edge up (nose down). Examination of the engine revealed extensive impact damage which precluded rotation of the crankshaft. Borescope inspection of all cylinders revealed the positions of the pistons relative to each other were in a normal pattern consistent with an intact crankshaft, and all valves were normal with no discrepancies noted. The camshaft was visually inspected with no discrepancies noted. Visual inspection of the valve train revealed no discrepancies. Examination of the air induction, ignition, fuel metering, lubrication, and exhaust systems revealed no evidence of preimpact failure or malfunction. Examination of the propeller revealed 2 blades were fully in the propeller hub and the other 2 blades (top) were displaced aft and partially attached. The propeller hub for both top blades were broken in that area. All blades exhibited evidence of chordwise or spanwise scratches on the cambered side of the blade. There was no evidence of preimpact failure or malfunction of the propeller assembly. MEDICAL AND PATHOLOGICAL INFORMATIONAn autopsy was not performed. Toxicology testing on specimens of the pilot was performed by the laboratory at FAA Forensic Sciences, Oklahoma City, Oklahoma. The toxicology report indicated no ethanol was detected in the muscle specimen, while an unquantified amount of lamotrigine was detected in the muscle specimen. According to the NTSB Medical Factual Report, records from the pilot’s primary physician for the 3 years preceding the accident were requested; records from a single visit in December 2019 were provided and reviewed. According to the records, the pilot had a history of prostate cancer, macular degeneration, and phantom limb pain from his amputation. According to these records, the pilot’s usual medications included tamsulosin and lamotrigine. Lamotrigine, often marketed with the name Lamictal, is approved for adjunctive treatment of epilepsy. Not uncommonly, it is used off-label for the treatment of neuropathy. Side effects include the potential for dizziness, tremors, somnolence, balance disorders, depression/suicidality, rash, and cardiac arrhythmias. TESTS AND RESEARCHNTSB review of over 53 years of airframe maintenance records revealed no entry indicating replacement of the up elevator control cable PN NAS304-35-2087 or turnbuckle eye P/N AN165-22RL associated with the up elevator control cable. The airplane’s most recent annual inspection was completed on May 1, 2020. The airframe maintenance log documenting that inspection noted, in part, “Inspected all flight controls and surfaces…” and “CW AD 2019-CE-036 replaced RH aileron control cable…” The airplane total time was 4,804.8 hours on the last entry dated December 12, 2020. According to the airplane Shop Manual that outlined 100-Hour or Annual inspection items, with respect to the rear fuselage/empennage, which was the location of the fatigue fractured turnbuckle eye, a check of the flight control cables, pulleys and associated equipment for condition, attachment, alignment, clearance, and proper operation was specified. The manual did not contain a focused inspection of the turnbuckle eye for wear of the cadmium coating or for cracks on the outer surface in the area of the turnbuckle. In January 2012, Hawker Beechcraft Corporation, the previous holder of the aircraft’s type certificate, issued Safety Communique 322 with the subject, “Flight Control Cable System Inspections.” The Safety Communique stated, in part, “Hawker Beechcraft Corporation (HBC) is issuing this Safety Communiqué to remind owners/operators of the importance of adhering to existing inspection procedures in the applicable Maintenance or Shop Manuals. Improper flight control cable system inspection for the airplanes defined in the MODELS section may result in undetected wear of the flight control cables.” The MODELS section included all piston aircraft. In July 2019, Textron Aviation, Inc., the current holder of the aircraft’s type certificate, issued Safety Communique 346 which stated, in part, “Gaining access and conducting thorough inspections on all sections of flight control cables and all turnbuckles should be an important part of completing periodic inspections.” Additionally, the Safety Communique included a copy of FAA Special Airwort
A loss of control inflight and the failure of a component of the up elevator flight control system due to fatigue, which rendered recovery from a right descending turn improbable.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
