- Location: Potrero, California
- Accident Number: WPR25FA062
- Date & Time: December 16, 2024, 10:30 Local
- Registration: N617GC
- Aircraft: AMERICAN EUROCOPTER LLC AS350B3
- Aircraft Damage: Substantial
- Defining Event: Medical event
- Injuries: 1 Fatal
- Flight Conducted Under: Public aircraft
https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/199430/pdf
https://data.ntsb.gov/Docket?ProjectID=199430
On December 16, 2024, about 1030 Pacific standard time, an American Eurocopter AS350 B3 helicopter, N617GC, was substantially damaged when it was involved in an accident near Potrero, California. The pilot was fatally injured. The helicopter was operated as a public use aircraft.
The pilot was scheduled to conduct a routine Customs and Border Protection (CBP) airsupport mission after several days of sick leave. Flight track data indicated that, after about 1.5 hours of flight, the helicopter entered a series of turns and a rapid descent. The final flight track point was about 820 ft above ground level and about 280 ft from the accident site. No further flight track data were available, and no eyewitnesses or surveillance video captured the accident flight.
A signal from an emergency locator transmitter (ELT) was received by a central rescue coordination center operated by the United States military, a typical routing procedure for ELT signals. The United States military subsequently communicated the detection to a division within the helicopter operator responsible for monitoring aircraft and receiving ELT signals. Without delays, the earliest a helicopter could have reached the accident site was about 10 minutes. The response was delayed by the time required to relay the ELT information among the responding organizations and by uncertainty concerning the coordinates supplied to the search crews, who located the wreckage about 53 minutes after the ELT began transmitting. A CBP emergency medical technician began CPR about 4 minutes later. The pilot’s autopsy identified a complete transection of the high cervical spinal cord, which would have prevented spontaneous breathing. The pilot also sustained multiple full-thickness heart lacerations and numerous other severe injuries. An NTSB medical analysis determined that the pilot’s injuries likely would have been rapidly fatal and that survival would have been highly unlikely even with an optimal rescue response. Therefore, the response time likely did not affect the pilot’s survivability.
Postaccident examination of the helicopter revealed no preimpact mechanical anomalies or malfunctions that would have precluded normal operation. The weather was clear with light wind, and the pilot made no radio transmissions reporting a problem or distress. For about the first 1.5 hours of the accident flight, flight track data indicated the pilot was actively and effectively controlling the helicopter while flying alone. The helicopter then entered a series of turns and a rapid descent that did not appear consistent with the preceding flight path or a normal approach to landing. The helicopter’s flight track, descent rate, and accident-site signatures indicated that it impacted the ground at a high rate of descent with substantial leftside loading in visual flight conditions without adverse wind. The available flight track data did not show a recovery attempt before the track ended. Given the absence of a preimpact mechanical malfunction, adverse weather, an external collision, or evidence of an intentional maneuver, pilot incapacitation was the most plausible explanation for the loss of contro
The Vehicle and Engine Multifunction Display (VEMD) recorded a main-rotor-speed exceedance of 466 rpm. The manufacturer determined that the exceedance was not associated with an engine power-turbine overspeed and was likely associated with main-rotor desynchronization (i.e., autorotation) during descent. Because no flight-control or cockpit recordings were available, the investigation could not determine the pilot’s control inputs or the circumstances that produced the exceedance.
An NTSB medical analysis identified severe multivessel coronary artery disease and evidence of prior heart-muscle damage, which significantly increased the pilot’s risk of a sudden impairing or incapacitating cardiovascular event. Although the autopsy did not identify evidence that such an event occurred, an autopsy cannot exclude a sudden cardiovascular event. Heart-rhythm disturbances generally leave no identifiable autopsy evidence, and a heart attack or stroke may leave no such evidence if it occurs shortly before death.
Alternatively, the pilot may have fallen asleep. Before the crash, the helicopter had been operating at a relatively stable altitude and a generally consistent track. The pilot had recently used diphenhydramine, a sedating antihistamine that can cause drowsiness. His recent respiratory illness also may have increased fatigue or sleepiness. However, available evidence was insufficient to determine whether the pilot experienced a cardiovascular event, fell asleep, or became incapacitated for another reason.
In accordance with CBP procedures, a clearance authority stationed at another base approved the flight. The clearance authority had no aviation background and would not have been familiar with the pilot’s normal demeanor. The required risk assessment did not address illness, medication use, or other human factors challenges, and the clearance authority did not know the pilot well enough to compare his demeanor with his usual behavior. However, the pilot reported that he had recovered from a cold, felt well, and had no symptoms other than a hoarse voice. The investigation could not determine when he used diphenhydramine or whether the clearance process could have identified or mitigated the condition that led to the loss of control. Therefore, the evidence was insufficient to identify the clearance decision as a contributing factor.
Based on the available evidence, the pilot likely lost control of the helicopter after becoming incapacitated. The pilot’s cardiovascular disease increased his risk of a sudden incapacitating cardiovascular event, while his use of diphenhydramine and recent illness may have increased his risk of falling asleep. The available evidence was insufficient to determine the specific cause of his incapacitation.
- Probable Cause:The pilot’s loss of control during cruise flight due to incapacitation for reasons that could not be determined.
- Pilot Information:
The 53-year-old pilot’s last aviation medical examination was August 7, 2024. At that time, he reported a medical history of high blood pressure treated with medication, seasonal allergies, acid reflux, and diet-controlled celiac disease (an abnormal autoimmune reaction to gluten). He was issued a second-class medical certificate without limitations.
The San Diego County Medical Examiner’s Office performed the pilot’s autopsy. According to the pilot’s autopsy report, the cause of death was blunt force injuries, and the manner of death was accident. Severe multivessel coronary artery disease was identified, including pinpoint narrowing of the left circumflex coronary artery, up to 80% narrowing of the right coronary artery, and up to 70% narrowing of the left anterior descending coronary artery by plaque. The lateral wall of the left ventricle contained a 2-cm area of old scar tissue. Moderate-to-severe plaque was present in the aorta.
The San Diego County Medical Examiner’s Office performed toxicological testing of postmortem blood specimens from the pilot. No tested-for substances were detected. A vitreous chemistry panel also was performed and was unremarkable.
The FAA Forensic Sciences Laboratory performed toxicological testing of postmortem specimens from the pilot. Diphenhydramine was detected in cavity blood at 186 ng/mL and in urine at 944 ng/mL. Doxylamine was detected at 65 ng/mL in urine and was not detected in cavity blood. Dapsone and its metabolite N-acetyl dapsone were detected in cavity blood and liver tissue, as were guaifenesin and acetaminophen. Dextromethorphan and its metabolite dextrorphan were detected in cavity blood and urine, as were losartan, hydrochlorothiazide, and amlodipine.
Diphenhydramine is a sedating antihistamine widely available over the counter in multiple sleep aids and cold and allergy products. Diphenhydramine can cause cognitive and psychomotor slowing and drowsiness and often carries a warning about driving and operating machinery. Because diphenhydramine can redistribute after death, its concentration in postmortem cavity blood cannot be reliably compared with impairment ranges established in living people. The FAA states that pilots should not fly within 60 hours of using diphenhydramine to allow time for it to be cleared from circulation.
Doxylamine is another sedating antihistamine medication that is available over the counter as a sleep aid and as an ingredient in various cold and allergy products. Products containing doxylamine often carry a warning about driving. The FAA states that pilots should not fly within 60 hours of using doxylamine to allow time for the drug to be cleared from circulation. Doxylamine was not detected in blood in this case.
Dextromethorphan is a cough suppressant medication that is available over the counter in a variety of cold and allergy products. Dextromethorphan is not typically impairing at concentrations associated with medicinal use. The FAA states that pilots who use dextromethorphan should observe a waiting period for the drug to be cleared from circulation before flying.
Guaifenesin helps loosen mucus and is available over the counter in various cold and allergy products. Acetaminophen is a pain- and fever-reducing medication widely available over the counter, including in cold and flu products. Guaifenesin and acetaminophen are not generally considered impairing.
Dapsone is a prescription medication. It is available in oral form to treat a variety of conditions, including itchy skin rash associated with celiac disease. Dapsone also is available in topical form for acne treatment. Although dapsone is not typically impairing, it sometimes may cause significant adverse side effects. According to the FAA medical case review for this accident, dapsone use is conditionally acceptable for pilot medical certification depending on the condition being treated and requires FAA review. It was not among the medications the pilot reported at his last aviation medical examination. N-acetyl dapsone is a metabolite of dapsone.
Losartan and hydrochlorothiazide are prescription medications commonly used to treat high blood pressure. Amlodipine is a prescription medication that can be used to treat high blood pressure and certain types of coronary artery disease. Losartan, hydrochlorothiazide, and amlodipine are not generally considered impairing. They were among the medications reported by the pilot at his last aviation medical examination.
According to the pilot’s wife, he would not have gone to work if he had been unable to perform his duties. During the weekend before the accident, the pilot spent time with his family and appeared to be feeling well. His wife did not hear him coughing. On the morning of the accident, the pilot slept normally, went for a run, and then went to work.
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