CEN18FA060

The pilot's low altitude flight into a power line due to his impairment from an acute physiologic event during the flight. Contributing to the pilot's impairment was his use of two sedating medications.

The private pilot was intending to conduct a cross-country flight when the light sport airplane collided with a power line and terrain. Several witnesses reported seeing the airplane flying at low altitude near the accident site. There were no eyewitnesses to the final portion of the flight; however, an individual near the accident site heard the airplane's engine from inside his residence. After the crash, he saw the airplane in the field outside his residence and flames from the power lines along the road. A postaccident airframe examination and operational engine test revealed no evidence of a mechanical malfunction or failure that would have precluded normal operation. The intended destination was 65 miles north-northwest of the departure airport. The accident site was located about 12 miles northwest of the departure airport, and according to engine data, the airplane crashed about 35 minutes after takeoff. The wreckage debris path was consistent with the airplane colliding with a 35-ft-tall power line while on a southerly heading. The pilot's partner reported that the pilot was familiar with the route of flight and that he had made the flight numerous times. She further noted that he typically flew at 3,500 ft mean sea level (msl) during cruise flight. A review of available air traffic control (ATC) radar data revealed no transponder or primary radar data associated with the flight. The lower limit of ATC radar coverage in the general area of the accident site was about 2,000 ft above ground level (2,750 ft msl). Based on the crash location, witness accounts, and the lack of ATC radar data for any portion of the flight, the pilot did not follow a direct route toward his intended destination or climb to his normal cruise altitude. According to toxicological test results, the pilot was using two impairing medications, diphenhydramine and gabapentin, which likely impaired him during the flight. However, he had likely used these drugs during previous flights where he did not demonstrate unusual behavior; thus, these medications alone do not explain the pilot's performance during the accident flight. The pilot remained at low altitude and in the general vicinity of the departure airport; he did not fly toward his intended destination, which suggests that he may have become confused about where he was, what he was doing, and where he was going. The pilot had several medical conditions that could have affected him during the flight; coronary artery disease, multiple previous ischemic and hemorrhagic strokes, and recent pneumonia. Another stroke or transient ischemic attack (TIA) during the flight could have made him confused or made it difficult to operate the airplane due to weakness in his arm and/or leg. The pilot's coronary artery disease and valvular heart disease could have also caused weakness and confusion due to low blood pressure as a result of an arrythmia, or an ischemia could have worsened his shortness of breath and caused him to become hypoxic (have low oxygen), which could also result in confusion. Any such physiologic event would have further worsened the psychoactive effects from the two sedating medications the pilot was using. Although the pilot was likely impaired by his use of two impairing medications, by themselves they do not explain the airplane's flight path and his behavior. Therefore, it is more likely that some physiologic event occurred that caused his inability to safely carry out the flight.

The Iowa Office of State Medical Examiner, Ankeny, Iowa, performed an autopsy on the pilot. The cause of death was attributed to multiple blunt force injuries. The medical examiner also identified atherosclerotic and thrombotic cardiovascular disease, and the probable component of positional asphyxia. Toxicological test results from the autopsy identified warfarin and diphenhydramine (0.062 ug/ml) in femoral blood. Clinical testing for electrolytes in vitreous were normal for postmortem results. The autopsy identified several areas of significant natural disease. At some point previously, the pilot had had his left lung completely removed. There was a scar in his larynx. The heart was enlarged, weighing 560 grams with right ventricular dilation and a floppy mitral valve. Average heart weight for a 215-pound man is 387 grams with a range of 293 to 511 grams. There was severe coronary artery disease with 50% stenosis of the left anterior descending vessel, 75% stenosis of the anterolateral distribution of the right coronary artery, and greater than 75% stenosis of the posterior descending branch. The right and posterior descending branches had areas of brown discoloration of the wall consistent with previous hemorrhage into the plaques. In addition, these vessels had partial occlusion of the lumen by intraluminal thrombus (clot). The remainder of the cardiac exam was unremarkable. A neuropathologist examined the brain as part of the postmortem examination. The cerebral vessels revealed moderate to severe atherosclerosis and the intracerebral vessels demonstrated vasculopathy that could not be specifically typed. There were lacunar infarcts (previous small strokes) scattered throughout the right and left frontal lobes and the right occipital lobe. There was an area of scar in the left frontal lobe consistent with a previous brain contusion. Toxicology testing performed at the FAA Forensic Sciences Laboratory identified atorvastatin, diphenhydramine (0.072 µg/ml), gabapentin (12.79 µg/ml), loratadine, losartan, metoprolol, sotalol, and warfarin in femoral blood. Except for loratadine and metoprolol, the above substances were also detected in urine. Metoprolol was detected in liver. The toxicology results were negative for carboxyhemoglobin in femoral blood and ethanol in vitreous. Diphenhydramine is a sedating antihistamine used to treat allergy symptoms and as a sleep aid. It is available over-the-counter under various names, including Benadryl and Unisom. Diphenhydramine carries the following warning: "May impair mental and/or physical ability required for the performance of potentially hazardous tasks (e.g., driving, operating heavy machinery)." Compared to other antihistamines, diphenhydramine causes marked sedation; it is also classed as a CNS depressant and this is the rationale for its use as a sleep aid. Altered mood and impaired cognitive and psychomotor performance may also be observed. In fact, in a driving simulator study, a single dose of diphenhydramine impaired driving ability more than a blood alcohol concentration of 0.100%. The range of blood levels thought to coincide with therapeutic and psychoactive effects from diphenhydramine is 0.0250 to 0.1120 µg/ml. Gabapentin, commonly marketed with the name Neurontin, is an antiseizure medication often used to treat nerve pain. The associated drug information warns that gabapentin may cause dizziness, somnolence, and other symptoms and signs of CNS (central nervous system) depression. The range of blood levels thought to coincide with therapeutic and psychoactive effects from gabapentin is 2.00 to 10.00 µg/ml. Metoprolol is a beta-blocker used to treat hypertension and to prevent recurrent heart attacks, commonly marketed with the names Lopressor and Toprol. Sotalol is another beta blocker with more prominent pro- and anti-arrhythmic effects. It is indicated for the treatment of life-threatening ventricular arrhythmias and atrial fibrillation with significant symptoms. Sotalol is associated with an increased risk of a life-threatening ventricular arrhythmia, Torsade de Pointe. Warfarin is a blood thinning medication used to prevent the formation of clots in patients with atrial fibrillation or other thrombotic disorders. Commonly marketed with the name Coumadin, treatment requires regular blood testing to ensure the degree of blood thinning remains in the desired range. It is associated with an increased risk of bleeding. Loratadine, commonly marketed with the name Claritin, is a non-sedating antihistamine available over-the-counter. Losartan is a prescription blood pressure medication commonly marketed with the name Cozaar. Atorvastatin is a cholesterol-lowering medication commonly marketed with the name Lipitor. These three medications as well as metoprolol, sotalol, and warfarin are not generally considered to be impairing. The pilot's personal medical records, obtained from the pilot's primary care provider for the period from January 1, 2015, through December 23, 2017, were reviewed by a National Transportation Safety Board Medical Officer. The first office visit during this period was on February 9, 2015, at which time the pilot's medical conditions included type 2 diabetes, hypothyroidism, hypertension, high cholesterol, sarcoidosis, a history of squamous cell cancer of the neck during 1999, a snoring disorder other than sleep apnea treated with continuous positive airway pressure (CPAP) (initial diagnosis July 2011), a transient ischemic attack (January 4, 2013) and a spontaneous intracranial hemorrhage (March 2013). The pilot had a previous hernia surgery as a child and bilateral carotid stents placed in January 2013 (left) and February 2013 (right). Over the subsequent years, the pilot remained off diabetes medication with a hemoglobin A1C that ranged from 6.1 to 6.9%. In July 2015, the pilot developed atrial fibrillation as a complication of sepsis from a urinary tract infection. In August 2015, the pilot was diagnosed with non-occlusive coronary artery disease by cardiac catheterization and underwent cardioversion that returned him to a normal sinus rhythm. Detailed catheterization results were not available in the primary care records. In June 2016, the pilot fell a couple of times at home and had lower-than-usual blood pressures. He had also developed a cough. The chest X-ray findings were initially thought to represent a pneumonia, but the symptoms failed to clear and additional evaluation demonstrated squamous cell lung cancer. In August 2016, the pilot underwent a left pneumonectomy, and in September 2016 had a central venous port placed in order to receive chemotherapy. He also received external beam radiation. During November 2016, the pilot developed peripheral neuropathy as a result of the chemotherapy with numbness and tingling in his fingertips and the bottoms of his feet and difficulty with balance. His strength and mobility improved with physical therapy and his subjective symptoms were treated with gabapentin. Records from November 26, 2017, indicate that the pilot had developed a cough, dizziness, and shortness of breath. He was admitted to the hospital with pneumonia in his remaining lung. He was discharged but returned to the emergency department with persistent symptoms and weakness and was readmitted. At his last outpatient visit, dated December 18, 2017, the pilot's daily medications included warfarin, losartan, metoprolol, gabapentin, magnesium, cholecalciferol (Vitamin D), cyanocobalamin (Vitamin B-12), pyridoxine (Vitamin B-6), atorvastatin, levothyroxine, diphenhydramine, sotalol, and loratadine. The pilot's partner stated that the pilot's health had been a "little off" from pneumonia during the previous 2 months. She noted that, on occasion, the pilot would hold onto her arm for support when walking. She added that the pilot's mental condition was normal for a 70-year-old individual. The airport manager at MIW re