ERA24FA078

A missing induction clamp, which allowed the induction hose to the left side intercooler to become disconnected, resulting in a total loss of engine power due to an overly rich fuel/air mixture.

The pilot departed his home airport for a short local flight. According to ADS-B data, the airplane flew for about 10 minutes before it began a return to the departure airport. About 8 minutes after turning back toward the airport, the airplane had a sudden decrease in groundspeed and began a descent. At the airplane’s last ADS-B position, it was at an altitude of 60 ft above ground level (agl) and less than 1 nautical mile (nm) from the threshold of the airport’s runway. The airplane subsequently struck trees about 40 ft agl, which separated the left elevator, and the airplane came to rest about 58 ft from the trees. A witness near the accident site reported hearing no engine noise from the airplane before impact. A sound spectrum study of audio captured by a security camera near the accident site revealed that, just before impact, the airplane’s propeller was rotating at a rate near 1,100 rpm, which was consistent with the engine at idle or windmilling. A postaccident examination of the airframe and engine revealed that an induction clamp was missing that connected the induction hose to the left side intercooler, and the induction hose coupling was displaced from the intercooler inlet. The induction clamp was not observed during any of the postaccident examinations. All spark plugs were carbon fouled, which was consistent with the engine operating with an overly rich fuel/air mixture. Although the fuel servo testing revealed that the servo was slightly rich at two test points, this small amount of excess fuel flow would not have precluded normal operation of the engine. Testing of the fuel pump revealed that it operated normally at all tested conditions except for the 650 rpm setting, which resulted in a low flow rate of 2 lbs per hour (below the specified 9 lbs per hour). However, the flow rate at 1,100 rpm was 90 lbs per hour, which would have been sufficient flow to support engine operation at idle rpm in flight. No other anomaly was found. Generally, when an induction hose that is downstream of a turbocharger compressor is disconnected from the rest of the induction system, the engine potentially loses a significant amount of manifold pressure. Based on the available information, it is likely that, due to the missing clamp, the induction hose coupling became disconnected from the left side intercooler, which resulted in an imbalance in the intake system, and the fuel mixture becoming overly rich. This would subsequently result in a loss of engine power. The reason the clamp was missing could not be determined as the clamp was not recovered. The postaccident toxicological testing results for samples from the pilot indicated that he had used the medication diphenhydramine, which has a potential to cause sedation and impairing effects. Although the pilot may have been experiencing impairing effects of the medication at the time of the accident, no more specific conclusions about his impairment could be drawn. Additionally, his autopsy report indicated cardiovascular disease, which is associated with increased risk of experiencing a sudden impairing or incapacitating cardiovascular event, such as heart attack or stroke. There was no autopsy evidence that such an event occurred; however, such an event does not leave reliable autopsy evidence if it occurs immediately before death.

Review of the airplane’s maintenance logbooks revealed that the engine was overhauled by the manufacturer on July 14, 2023. A maintenance record dated August 15, 2023, indicated that, during the engine installation, both turbochargers were removed and temporarily replaced with serviceable units so that the actions specified in Lycoming Special Advisory SA-203 and Hartzell Engine Technologies Service Bulletin SB-203 could be completed on the removed turbochargers. The last annual inspection was performed on August 15, 2023, at an airframe total time of 1,208.6 (48.2 hours before the accident). On September 18, 2023, at an airfame total time of 1,211.3 hours (45.5 hours before the accident), the left and right turbochargers were reinstalled (after the special advisory and service bulletin actions were completed). The pilot’s last aviation medical examination was November 5, 2022. At that time, he reported a history of high blood pressure, which was noted to be qualified under Conditions Aviation Medical Examiners Can Issue (CACI) criteria. The pilot reported using losartan, which is a prescription medication commonly used to treat high blood pressure. The pilot was issued a third-class medical certificate limited by a requirement to have available glasses for near vision. The pilot’s autopsy was performed at Wake Forest Baptist Medical Center in the North Carolina Medical Examiner System. According to the pilot’s autopsy report, his cause of death was multiple blunt force injuries, and his manner of death was accident. The pilot’s autopsy identified mild-to-moderate multivessel coronary artery disease, moderate calcific stenosis of the aortic valve, and moderate ulcerated plaque in the abdominal aorta. The remainder of the autopsy, including visual examination of the heart, did not identify other significant disease. FAA Forensic Sciences Laboratory postmortem toxicological testing detected diphenhydramine in aortic blood at 42 ng/mL and in urine at 576 ng/mL. Diphenhydramine is a sedating antihistamine medication 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. The FAA states that pilots should not fly within 60 hours of using diphenhydramine, to allow time for it to be cleared from circulation. On December 31, 2023, at 1213 eastern standard time, a Piper PA-46R-350T, N539MA, was substantially damaged when it was involved in an accident near Mooresville, North Carolina. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. A family member reported that the pilot intended to take the airplane for a short local flight then refuel it for a family trip planned for the next day. According to ADS-B data for the accident flight, the airplane departed from runway 32 at Lake Norman Airpark (14A), Mooresville, North Carolina, about 1152 and climbed to an altitude of about 3,000 ft mean sea level (msl) on a northwest ground track, following the Catawba River for about 30 nm. The data showed that, at 1202, the airplane turned left then flew a direct course back toward 14A. The airplane’s ground speed was about 200 kts for the entire flight until about 1210, when it decreased, and the airplane began a descent. The airplane’s last ADS-B position was recorded at 1213. It showed that the airplane was at an altitude of 850 ft msl, which was about 60 ft agl. The accident site was about 488 ft southeast of the last ADS-B position, which was about 3/4 nm from the threshold of runway 14. A witness located near the accident site reported hearing no engine noise from the airplane before the impact. A security camera located at a private residence captured both video and audio of the accident airplane. The airplane was visible for 9 seconds as it traveled from right to left across the camera’s field of view, then the sound of impact occurred about 3 seconds later. When the airplane entered the camera’s field of view, it showed minor roll oscillations, its propeller was turning, then it started to bank to the right and lose altitude before it exited the field of view. A sound spectrum study performed on the captured audio calculated that the propeller rotation was about 1,100 rpm, which was consistent with the propeller windmilling. Examination of the accident site and wreckage revealed that the airplane came to rest upright about 58 ft southeast of a severed treetop that was broken about 40 ft agl. A ground scar about 18 ft long and oriented to 159° true led up to the airplane. Several trees exhibited impact damage, and fallen branches were along the debris path. There was no evidence of fire, and all major components of the airplane were recovered from the accident site. The fuselage, right wing, and most of the empennage remained intact. The left wing was impact fractured and resting inverted on top of the right wing. The left horizontal stabilizer was located in front of the cockpit, and the left elevator was separated and found in a tree. The right wing remained attached by the aft wing attachment. Both main wing spars were fractured at the respective wing root, and both wings exhibited damage consistent with tree impact. The flaps and landing gear were retracted. Both the left and right wing fuel tanks contained fluid consistent in odor and color with 100LL aviation fuel. The fuel vents were examined and both the main fuel vent systems contained reddish colored dirt, which was similar to the dirt surrounding the airplane at the accident site. The left main fuel vent system was completely obstructed, and the right main fuel vent system was only partially obstructed. The left fuel tank vented cap was tested and found to operate normally. The fuel selector handle was positioned to the left tank. The emergency fuel pump switch was in the “ON” position. The engine remained attached to the fuselage at the engine mount. The three-blade, constant-speed propeller remained attached to the engine and was impact damaged. Two of the three composite propeller blades were detached at the blade roots. The blade that remained attached to the propeller hub displayed chordwise tears. One of the detached blades was fractured. None of the blades displayed chordwise abrasion, twisting, or bending, and no leading-edge damage was observed. The throttle, propeller, and mixture levers were in their full forward positions. Flight control cable continuity was confirmed from the cockpit area to each of the respective control surfaces through separations consistent with accident forces. Examination of the engine revealed continuity of the crankshaft to the rear accessory gears and to the valvetrain. Thumb compression and suction were observed from all cylinders when the crankshaft was rotated. The left and right magnetos were removed, and sparks were observed on all towers when each magneto’s input driveshaft was rotated. Examination of the engine’s cylinders with a lighted borescope revealed no anomaly. The top spark plugs were removed and showed signs of heavy carbon deposits. The emergency fuel boost pump was removed and operated when electrical power was applied. Air was applied and flowed throughout the fuel lines. When the fuel flow divider was removed and disassembled, a small amount of fluid consistent with 100LL aviation fuel was found in the flow divider. No contamination was noted, and the diaphragm was in good condition. Examination of the induction system found that the induction hose that connected to the left side intercooler was missing the clamp, and the hose coupling was displaced from the intercooler. The clamp was not observed during the examination. The engine was shipped to the manufacturer for further examination. All six cylinders were removed from the crankcase assembly; the cy