ANC14FA030

The pilot's loss of control of the helicopter due to impairment or incapacitation from a sudden, acute cardiac event.

***This report was revised on November 29, 2017. Please see the docket for this accident to view the original report.*** The accident flight was one of several recent practice external-load flights that the pilot had been conducting with a 150-ft long-line and weighted barrel. The helicopter approached the airport from the north and then hovered over the approach end of runway 20R. At the time, two airplanes were in the airport traffic pattern for runway 20R, another was in the airport vicinity, and a fourth was departing from runway 2R toward the hovering helicopter. One witness reported hearing the accident pilot attempt to communicate with the departing northbound airplane, but no response was heard, and the airplane passed close to the helicopter. After the northbound airplane passed by, the helicopter moved to its normal landing area on the east ramp, and the accident pilot responded to another pilot's query as to his intentions by stating that he was landing. Immediately after the pilot's response, the helicopter suddenly pitched up, rolled left, and descended to the ground.   Examination of the helicopter revealed no evidence of preimpact mechanical anomalies with the airframe, systems, or powerplant. Damage to the main rotor and associated ground scars and wreckage distribution were consistent with the rotor system operating at normal rpm during the impact sequence. Damage to the helicopter and the location of the main rotor ground scar were consistent with the helicopter having collided with the ground in an extreme left roll. The long-line remained attached to the barrel but was not attached to the helicopter's cargo hook, and the disconnected end was near the main wreckage. The relative orientation of the long-line and the main wreckage indicated that the line was still attached to the helicopter when the helicopter moved laterally at some point; however, no known witness observed when or how smoothly the line and load were released. Maneuvering a helicopter to land during external load operations requires precision in both helicopter control and timing of load release. Although the accident pilot's workload was increased by the demands of maintaining traffic separation and communicating on the radio in the busy, nontowered airport environment, there was no evidence to suggest that such an operation was beyond his skill level, particularly given his recent practice. The accident pilot was based at BCV and, in the 2 weeks before the accident, had conducted seven flights (including the accident flight) with a 150-foot long-line in the accident helicopter; in the preceding 90 days, the pilot had flown almost 60 hours, most of which involved autorotations, hover maneuvers, and long-line practice. The pilot's autopsy identified severe coronary artery disease with greater than 75% stenosis in two main arteries. In addition, scarring in the left ventricle was identified, which indicated that the pilot had experienced a previous heart attack. Although the pilot had sought and received in recent years medical care that included cardiac testing, there is no evidence that his previous heart attack was ever diagnosed (research has shown that the tests are not always accurate). Given the presence of two severely stenotic lesions in two main arteries and the presence of scarring from a previous heart attack, the accident pilot's likelihood for experiencing another acute cardiac event (such as a new heart attack, anginal symptoms, or an acute arrhythmia) was inevitable. An acute cardiac event would likely cause symptoms ranging in severity from impairing (such as chest pain and shortness of breath or palpitations) to incapacitating (fainting from low blood pressure or sudden cardiac death). Further, such an event occurring immediately before impact would likely leave no identifiable evidence on autopsy. Considering the precision required while maneuvering to land with an external load, any level of impairment could result in catastrophic consequences; therefore, the pilot likely experienced a sudden, acute cardiac event that adversely affected his performance.

BCV, elevation 83 ft msl, was located 2 miles northwest of Chugiak, Alaska. BCV was a nontowered airport with a 4,010 ft x 100 ft asphalt runway (2L/20R) and an 1,800 ft x 50 ft runway (2R/20L). The CTAF was 123.0 MHz. Hydraulic Servos for Main Rotor Flight Controls Visual examination of the three D212-1 hydraulic servos (forward right, forward left, and aft servo) at the Robinson Helicopter factory revealed nominal impact-related damage. The fluid inlet screen for each servo was clear, and the hardware torque stripe on each was unbroken. All three servos were fitted with factory fluid fittings and supply and discharge hoses and were connected to a factory hydraulic test bench for functional testing. The testing revealed that all three servos functioned within limits with no anomalies noted. Clutch Strut Examination of the clutch strut under magnification in the NTSB Materials Laboratory showed linear scrape damage across one side of the strut fittings at one end. The State of Alaska Medical Examiner's Office, Anchorage, Alaska, performed an autopsy on the pilot. The report listed the pilot's cause of death as "multiple blunt force injuries" and noted that the thermal injuries were sustained postmortem. The autopsy report also noted focal areas of greater than 75% atherosclerotic stenosis in both the mid left anterior descending coronary artery and the distal right coronary artery; the other coronary arteries showed scattered calcific atherosclerosis without significant stenosis. Focal white scarring was identified in the posterior left ventricle consistent with a remote myocardial infarct (heart attack). Microscopic evaluation of the heart identified the area as "confluent fibrosis consistent with remote infarct." The FAA Bioaeronautical Sciences Research Laboratory in Oklahoma City, Oklahoma, performed forensic toxicology on specimens from the pilot. The report stated that no carbon monoxide was detected in the blood, no ethanol was detected in the vitreous, and 33.4 (ug/ml, ug/g) salicylate was detected in the urine. (Salicylate is a metabolite of aspirin.) Medical History Review of the medical records from the pilot's primary care physician found that, in March 2011, a coronary calcium score test was ordered to evaluate the pilot's risk of coronary artery disease. The result was a total coronary artery calcium score of 919, which included 361 in the right coronary and 335 in the left anterior descending. (According to the record, a total score over 400 indicates a very high likelihood of significant atherosclerosis in at least one main coronary artery.) The pilot subsequently underwent a stress test on March 25, 2011, and exercised to 14.9 metabolic equivalents of task without symptoms. The electrocardiogram (ECG) portion of the test demonstrated some non-diagnostic ST segment depression inferiorly at peak heart rate and during the post-exercise recovery period. (The ST segment is the section of an ECG between the end of the S wave and the beginning of the T wave.) A note from the physician in the record suggested that this was a thallium stress test, but the record contained no radiology report. According to the records, on March 6, 2012, the pilot's blood pressure was 142/80. On April 30, 2013, the pilot underwent a physical examination that was unremarkable. A letter from the physician to the pilot described an elevated glucose level, but the record contained no laboratory results that specified the glucose level. A research study published in 2012 found that the sensitivity for stress testing for significant stenosis is 77%, even when the person reaches maximal exertion and with the addition of nuclear imaging (a thallium stress test). (Source: Al Aloul et al. 2012. "Utility of nuclear stress imaging for detecting coronary artery bypass graft disease." BMC Cardiovascular Disorders, 12:62.) Initial examination of the helicopter at the accident site revealed that the fuselage came to rest on its left side on a gravel area south of the paved airport ramp, and most of the cockpit and cabin structures were consumed by fire. The engine and skids were on the ground near the fuselage and showed thermal damage. The tailcone and tail rotor were primarily intact and on the ground aft of the burned fuselage, which was generally oriented facing northwest. A linear scar was adjacent to the burned fuselage; the length of the scar was consistent with the length of a main rotor blade. The main rotor gearbox and mast assembly with the main rotor hub attached was found separated on the ground an estimated 100 ft north of fuselage and engine, at the edge of the paved ramp and adjacent to a separated taxiway light. One main rotor blade was separated outboard of the hub near the blade root, and the other main rotor blade was attached in its entirety and damaged. All separated pieces of main rotor blade were located at the accident site. The barrel with which the pilot had been practicing was found on its side in the grass adjacent to the airport ramp. (A witness reported that the pilot typically lowered the barrel such that it remained upright.) The barrel, a 55-gallon steel drum, was about three-quarters filled (estimated) with water. The long-line was attached to the barrel, and the other end was not attached to the helicopter's cargo hook. The line extended on the ground from the barrel generally southwest toward the main wreckage and was looped on the ground adjacent to the main wreckage; the end of the line was on the ground about 20 ft southwest of the main wreckage. Visual examination of the ramp area, barrel, and line revealed no scrape, drag, or contact marks that could be identified as uniquely associated with the accident. (The ramp area had multiple scrape marks, most of which were presumably from winter snow removal activity, and the barrel had multiple scrape marks in several areas.) Examination of the long-line revealed it consisted of three 50-foot sections of 3/8-inch braided nylon rope, each of which included a 1/2-inch rope thimble spliced at each end. The ropes were connected together by aluminum carabiners with locking gates. The barrel end of the long-line was attached to a hook through two aluminum carabiners with locking gates and a swivel adapter between them. The hook was attached to a barrel harness, which was secured around the barrel. The helicopter end of the long-line terminated at the 1/2-inch rope thimble with no ring or other rigging structure attached. Postaccident examination of the wreckage at a recovery facility revealed that the upper and left sides of the airframe sustained extensive impact damage. The main rotor drive shaft was crushed and bent about 15° at the teeter stop. The three D212-1 hydraulic servos (forward right, forward left, and aft servo) for the main rotor flight controls were removed from the wreckage and retained for further examination. One main rotor blade was attached to the root and fractured in two places with its fractured segments attached by the trailing edge doublers. The separated surfaces were angular and jagged, and the blade was bowed upward about 6 ft outboard of the hub, and the outboard 6 ft were bent forward in the direction of rotation. The leading edge had many small dents with coarse scuff marks running chordwise along the entire blade. There was a large puncture in the blade afterbody from the upper skin into the lower skin. The other main rotor blade was separated near the root, and the separations were angular and jagged. Both the inboard side and the outboard side of the disconnect had corresponding coarse scuff marks running mostly chordwise on the upper skin. This blade was bent forward in the direction of rotation at mid-span, and the afterbody in the same area was fractured from the trailing edge toward the spar at a slight angle. The surfaces of the fractured skins were angular and jagged. The leading edge of the upper skin at the tip ha