ERA12FA484

Maintenance personnel’s improper lubrication of the right direct aileron control cable and failure to detect the severe corrosion of the cable during a maintenance inspection, which resulted in the in-flight failure of the cable, the pilot’s subsequent inability to maintain aircraft control, and the airplane’s impact with terrain.

About 4 minutes before the accident, the pilot advised an air traffic controller that an aileron cable had broken but that he was continuing to the airport to land. Security video and eyewitness reports revealed that the airplane was at low altitude and appeared to be maintaining level flight until it banked right, descended, and impacted water near the airport in a right-wing-down attitude. A postaccident examination of the wreckage indicated that all of the airplane's flight control cables were lubricated except for a fractured section of aileron control direct cable near the doorpost pulley, which was likely not properly lubricated. Most of the cable strands and the doorpost pulley and bearing exhibited severe corrosion near the fracture. When manipulated by hand, the pulley bearing would not rotate due to the corrosion. Analysis of the cable, doorpost pulley, and an exemplar cable from a similar make and model aircraft that had been flown in similar atmospheric conditions (in what is considered a severe corrosion zone) revealed moderate to severe corrosion. It is likely that, during the airplane's maintenance inspection 6 months before the accident, the mechanic failed to detect the corroded cable due to the difficulty in visually seeing the cable. It is also likely that the doorpost pulley's failure to rotate resulted in tension on the right aileron control cable, which subsequently caused it to fail due to the severe corrosion. The aircraft manufacturer's maintenance manual for the airplane gives specific instructions for lubricating and inspecting flight control cables and pulleys every 600 hours or 12 months, whichever comes first, including, in part, examining the cables for corrosion and the pulleys to ensure smooth rotation. After the accident, the manufacturer produced a video emphasizing the importance of properly examining and lubricating the cables.

HISTORY OF FLIGHT On July 25, 2012, about 1420 Atlantic time zone (AST), a Cessna 172M, N73115, was substantially damaged when it impacted the water near Fernando Luis Ribas Dominicci Airport (TJIG), San Juan, Puerto Rico. Visual meteorological conditions prevailed and a visual flight rules flight plan had been filed. The private pilot was fatally injured. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. The flight originated from Antonio/Nery/Juarbe Pol Airport (TJAB), Arecibo, Puerto Rico. According to numerous eyewitness reports, the airplane appeared to be maintaining level flight and subsequently banked to the right, as viewed from behind, descended, and then impacted the water in a right-wing-down attitude. One eyewitness, located in an aircraft that was following the accident airplane on final approach, reported that the airplane "made some zigzagging" prior to it banking to the right. The airplane was observed impacting the water's surface with the right wing tip. The airplane then cartwheeled and disappeared below the water's surface. According to video taken of a security video monitor, from a camera mounted on a terminal building on the southwest side of the bay, the airplane banked to the right and remained in a continuous bank. The airplane turned about 180 degrees of heading change, facing the direction of travel prior to impacting the water. The airplane was observed impacting the water in a right-wing-low attitude and, within about 2 seconds, disappeared below the water's surface. PERSONNEL INFORMATION According to Federal Aviation Administration (FAA) records, the pilot held a private pilot certificate with an airplane, single engine land rating. The most recent logbook entry that was located, dated September 30, 2011, indicated he had 1,150.9 total hours of flight time. According to information provided on his most recent third class medical certificate application, issued March 3, 2012, he reported 1,175 total hours of flight time. The medical certificate was issued with a limitation for the requirement to wear corrective lenses, and not valid for any class after. AIRCRAFT INFORMATION According to FAA records, the airplane was issued an airworthiness certificate on May 14, 1976 and was registered to the pilot on December 2, 2002. It was equipped with a Lycoming O-320-E2D engine, serial number L-45584-27A. A review of copies of maintenance logbook records showed an annual inspection was completed April 13, 2012, at a recorded tachometer reading of 2,999 hours, and engine time since overhaul of 2,928.0 hours. The tachometer and Hobbs meter were observed at the accident site and indicated 3,009.6 hours and 586.0 flight hours, respectively. The most recent entry that specifically stated when any control cables were lubricated was recorded on January 22, 2010, at a tachometer reading of 2,913.2 hours, and that wan an engine logbook entry. According to an airframe and powerplant (A&P) mechanic, he performed most of the maintenance and on the day of the accident he serviced the nosewheel strut, which was "low." He also performed the last annual inspection; however, he was unsure of the date. According to the inspection authorization (IA) mechanic who signed off on the annual inspection, it was completed about six months prior to the accident. METEOROLOGICAL INFORMATION The 1422 recorded weather observation at TJIG included wind from 110 degrees at 8 knots, visibility 10 miles or greater, scattered clouds at 4,000 feet above ground level (agl), temperature 32 degrees C, dew point 24 degrees C and barometric altimeter setting 30.03 inches of mercury. COMMUNICATION At 1413:00, the pilot made his initial contact with the TJIG Federal Contract Air Traffic Control Tower controller and was subsequently told to make a straight in approach to runway nine and report at the Levittown water tank. At 1416:28, the pilot reported abeam the Levittown water tank. At 1418:13, the pilot stated, "november one one five tower." At 1418:15, the local controller replied, "november one one five tower." At 1418:17, the pilot replied, "i think i got my aileron cable broken ah i am unable to maintain level flight so i'll continue the descent and land." At 1418:27, the tower controller replied, "november one one five you're cleared to land runway niner wind one one zero at six do you require any assistance." At 1418:33, the pilot stated, "i don't know i guess not." No further recorded transmissions were received from the accident airplane. At 1422:09, the pilot of another aircraft, which was in the area, reported that the airplane had crashed into the water. WRECKAGE AND IMPACT INFORMATION According to U.S. Coast Guard channel charts, the airplane was found submerged in approximately 44 feet of water, 1,490 feet from the threshold of runway 9, the intended landing runway. The wreckage debris was located slightly to the south of the extended centerline for runway 9. The main wreckage was located in a generally compact area. According to photographs provided to the NTSB during the night recovery operation, the airplane came to rest inverted and was resting on the floor of the bay. Right Wing The right wing remained attached to the forward attachment point and all access panels remained in place. Crush damage was evident on the outboard 3 feet, 3 inches of the wing structure . The trailing edge wing root exhibited compression fractures from the attachment point of the fuselage, outward for about 4 feet, 1 inches. The outboard 21 inches of the right wing aileron was bent slightly in the negative direction, and the inboard section of the wing flap, about 24 inches in length, exhibited damage that was similar to crush damage. The wing strut was bent in the negative direction about 27 inches from the wing attach point. The right flap drive motor worm gear was measured at 2.5 inches, which correlated to a 10-degree flap position. The aileron and flap remained attached to their respective attachment points. The interconnect control cable to both ailerons exhibited broomstrawing and the control cable associated with the right aileron was separated in a manner consistent with tensile overload. The top left doorpost pulley exhibited signs of scoring on the pulley rim. A section of the right aileron control direct cable, which exhibited signatures consistent with corrosion at the failure point, and its associated pulley, were removed and sent to the NTSB Materials Laboratory for examination. The other cables did not exhibit signs of excessive corrosion at the failure points. All cables appeared to have had a lubricant applied and were oily in nature; however, a section of cable on the aileron control direct cable at the fracture point was devoid of lubrication. Empennage The empennage exhibited impact damage and fractures aft of the cargo compartment and remained attached to the cabin area by rudder and elevator cables. Continuity to the rudder from the rudder pedals was confirmed. Continuity from the elevator to the empennage fracture point and then forward to the base of the cockpit control column was confirmed. The trim tab was found at the 10-degrees trailing edge up setting. The emergency locator transmitter (ELT) remained secured and attached to the sidewall of the empennage. The ELT switch was found in the "ON" position; however, no reports of an ELT activation were reported. The ELT had a label affixed with the following notation, "Replace Battery June 2014." Examination of the ELT revealed saltwater intrusion and corrosion on the internal mechanism and batteries. Left wing The left wing remained attached at the attachment point, and all access panels remained in place. The outboard 8 feet, 10 inches, as measured from the wingtip, of the leading edge exhibited crush damage. The aileron and flap remained attached. The wing flap