WPR22FA350

The pilot’s in-flight incapacitation due to G-induced loss of consciousness, which resulted in a subsequent impact with terrain.

The pilot of the accident airplane was participating in a closed-course air race and was varying between first and second place. During the 3rd lap of 6, the accident airplane began a climb as it neared outer pylon No. 4, where it appeared to tighten its left turn toward the inner portion of the racecourse. At the peak of the climb, the airplane entered an approximate 90° right bank and started a descent before it rolled left to an approximate 90° left bank. The airplane continued to descend in a steep left bank and nose-low attitude until it impacted terrain just beyond outer pylon No. 5. Postaccident examination of the airplane revealed no evidence of any preexisting mechanical malfunction that would have precluded normal operation. As the airplane rolled 90° right and pitched up, followed by a 180° left roll and descent, the pilot’s lack of control inputs following the roll indicated that the pilot likely experienced an onset of higher G loads during the left roll, which ultimately led to G-induced loss of consciousness (G-LOC). The reason for the pilot’s initial roll to the right is unknown; however, it’s likely that the pilot’s aggressive roll to the left was an effort to maintain his position in the race. It is possible that the pilot’s coronary artery disease and/or amlodipine use may have reduced his G-tolerance; however, the investigation was unable to determine if the pilot’s medical conditions or medication use contributed to the accident.

According to Federal Aviation Administration (FAA) records, the 61-year-old male pilot’s last aviation medical examination was June 14, 2022. At that time, his reported medical history included high blood pressure, which the aviation medical examiner (AME) noted was under control and met Conditions AMEs Can Issue (CACI) criteria. The pilot’s reported medical history also included low testosterone treated with medication, and a previous episode of chest pain in 2016 that led to a diagnosis of non-obstructive coronary artery disease; for these conditions, the pilot had been granted Authorization for Special Issuance of medical certification by the FAA. At his most recent aviation medical examination, the pilot reported using the medications losartan and amlodipine (prescription medications used to treat high blood pressure), testosterone and anastrozole (prescription medications used to treat low testosterone), and valacyclovir (a prescription antiviral medication used as needed to treat cold sores). No significant issues were identified, and the pilot was issued a second-class medical certificate with the limitation, “Not valid for any class after 06/30/2023.” The pilot’s FAA medical certification records documented that he underwent cardiac catheterization for coronary angiography in October 2017, after an abnormal nuclear stress test in 2016 for an episode of atypical chest pain. The 2017 cardiac catheterization demonstrated mild multivessel coronary artery disease (maximum stenosis approximately 25-30%), not requiring intervention, with intact left ventricular function. In November 2018, the pilot completed the process to obtain an Authorization of Special Issuance for third-class medical certification for non-obstructive coronary artery disease, low testosterone, and use of medication. Subsequent authorizations were issued in August 2019 (for third-class medical certification), September 2020 (for second-class medical certification), and July 2021 (for second-class medical certification). Additional cardiac testing documented in FAA files included a May 2019 nuclear stress test, May 2020 echocardiogram, June 2020 and June 2021 exercise stress tests, and (most recently) April 2022 exercise stress echocardiogram. These tests were without diagnostic findings of ischemia. The 2020 echocardiogram showed mild left ventricular hypertrophy with a normal ejection fraction. The April 2022 stress echocardiogram was interpreted by a cardiologist as being normal (including normal left ventricle size and systolic function, without evidence of inducible ischemia) and representative of very good exercise tolerance. The pilot’s two most recent Special Issuance Authorization letters included the warning, “Your heart disease places you at increased risk of in-flight cardiac impairment and sudden incapacitation when performing maneuvers involving increased G-forces. This is in addition to the baseline risk of G-LOC. For further information, please refer to FAA Advisory Circular AC-91-61 which can be downloaded here: [web address provided].” The Washoe County Regional Medical Examiner’s Office performed the pilot’s autopsy. According to the pilot’s autopsy report, his cause of death was blunt force injuries and his manner of death was accident. The extent of the pilot’s injuries prevented structural evaluation of the heart and lungs, and the brain was not available for examination. Within these severe limitations, the autopsy did not identify significant natural disease. At the request of the Medical Examiner’s Office, NMS Labs performed postmortem toxicological testing of muscle tissue from the pilot. Caffeine was presumptively detected. No other tested-for substances were detected. The FAA Forensic Sciences laboratory also performed toxicological testing of postmortem specimens from the pilot. This testing detected amlodipine in muscle and heart tissue. No blood was available for testing. Caffeine is a central nervous system stimulant that is commonly ingested, including in coffee, tea, soft drinks, and chocolate; it is also an ingredient in certain anti-drowsiness medications and headache medications. Caffeine is not generally considered impairing. Amlodipine is a prescription long-acting dihydropyridine calcium channel blocker medication that can be used to treat high blood pressure and certain types of coronary artery disease. Amlodipine is not generally considered impairing and is one of the acceptable medications under the FAA’s CACI criteria for hypertension. However, because amlodipine acts by dilating peripheral blood vessels, in theory the drug may adversely affect G tolerance. The US Air Force does not permit amlodipine use by its high-performance aviators. To a seated pilot, high positive vertical G force feels like being pushed down into the seat. Such force may be experienced during maneuvers such as high-speed turns or pull-up maneuvers. High positive vertical G force makes it harder for the heart to effectively pump blood to the brain. In some cases, this may result in brain hypoxia and G-induced loss of consciousness (G-LOC). Generally, when blood pressure to the brain drops too low, the body attempts to compensate by reflexively increasing heart rate and the volume of blood pumped with each heartbeat, and by constricting peripheral blood vessels. However, this response typically takes at least 6-9 seconds, and sometimes is not enough to prevent G-LOC. The physiologic reserve of brain function in the absence of blood flow is about 4-6 seconds. In G-LOC, a pilot loses awareness, muscle control, and consciousness, and is unable to control the airplane. Once the vertical G force is reduced, a pilot who has experienced G-LOC will remain absolutely incapacitated by unconsciousness for a period, and then, upon regaining consciousness, will experience an additional period of relative incapacitation by confusion and disorientation. This results in a period averaging about 20-30 seconds after G force is reduced during which the pilot remains unable to control the airplane. Upon recovery from G-LOC, a pilot may not realize that it has occurred. Vision loss (“tunnel vision,” “gray-out,” or “blackout”) due to diminished retinal blood flow might also occur with exposure to high positive vertical G force. Such vision loss may precede G-LOC, but does not reliably do so, particularly with rapid onset of high positive vertical G force, which can cause G-LOC to develop without warning. It is also possible for pilots to experience “almost loss-of-consciousness” (A-LOC) after short-duration, rapid-onset pulses of positive vertical G force. A-LOC is characterized by cognitive impairment, disorientation, and sensorimotor disturbance of shorter duration than G-LOC. Multiple variables affect an individual’s G tolerance at any given time, including heart-to-brain distance, use of anti-G measures (such as an anti-G suit or an anti-G straining maneuver), hydration, nourishment, fatigue, physical conditioning (although aerobic conditioning without resistance training may actually decrease a person’s ability to compensate for G force), medical conditions, use of substances, experience and recency of G force exposure, and other factors. Examination of the accident site revealed that the airplane impacted terrain on a heading of about 229° magnetic. The first identified point of contact (FIPC) with terrain was a swath of freshly disturbed dirt, consistent with a left-wing impact. The swath of disturbed dirt continued for about 180 ft to a large burn area. The 2,200-ft-long debris path continued along a heading of about 242° degrees magnetic and contained various fragments of wreckage along with portions of both wings, empennage, and engine. The wreckage was recovered to a secure location for further examination. Figure 3: Aerial view of the accident site provided by Nevada State Patrol, with annotations