Accident Details
On April 6, 2024, at approximately 1350 eastern daylight time, a Robinson R-44, registration N234ZT, sustained substantial damage in an accident near Key Biscayne, Florida. The pilot, the sole occupant, was seriously injured. The helicopter was being operated as a personal flight under Title 14 Code of Federal Regulations Part 91.
Pilot Account
The pilot reported that he departed from Miami Executive Airport (TMB) in Miami, Florida, after topping off the fuel tanks and completing a preflight inspection. He was flying under a visual-flight-rules (VFR) flight plan with VFR flight following services to North Eleuthera Airport (MYEH) in the Bahamas. About 20 minutes after departure, after leveling off, he felt a brief "jerk." He recalled a similar sensation the previous week, which he attributed to a thermal or gust. Despite no caution/warning lights or aural warnings and all engine gauges indicating normal ranges, he turned back toward land as a precaution. A minute later, he felt another "jerk" and descended to 500 ft above ground level while applying carburetor heat. Shortly thereafter, he experienced a longer "shake" and declared an emergency. He heard unusual engine sounds and noticed he had to add power as the helicopter decelerated. While maneuvering toward land, he felt a vibration, heard the low main rotor rpm horn, and the engine lost significant power. The pilot initiated an autorotation, and the helicopter entered the Atlantic Ocean at about 35 knots, approximately 1 nautical mile from Key Biscayne. The empennage was substantially damaged, and the aft portion of the tail section was impact-separated.
Wreckage Examination
The wreckage was recovered and examined. The tail rotor system and gearbox were not recovered from the ocean. Postaccident examination of the airframe revealed that the gascolator bowl contained a mixture of liquid consistent with aviation fuel, a clear liquid that appeared to be water, and a small amount of rust-colored liquid. About 22 gallons of fuel and 20 gallons of water were removed from the fuel tanks. A minimum fuel flow test for the main tank yielded results within acceptable limits. The carburetor heat was extended about 2.3 inches, and the down-latch was not engaged. The carburetor heat valve air filter housing was partially open.
Examination of the engine showed evidence of saltwater and saltwater corrosion. The crankshaft could not be rotated when attempting to turn the cooling fan by hand. The crankcase contained about 2 gallons of salt water, and the oil quick drain was obstructed with sludge. The remaining oil was sufficient for operation. All six cylinders were removed; the No. 5 cylinder was difficult to remove and had blackened salt-like deposits between the cylinder and wall. All cylinders had varying salt deposits and heavy corrosion consistent with saltwater submersion. With cylinders removed, crankshaft and camshaft continuity was confirmed. Valve movement was normal after corrosion was freed. Salt deposits and corrosion were found throughout the carburetor. The fuel inlet screen had saltwater contamination. Both magnetos were filled with salt deposits and corroded; no spark was produced when rotated. The engine governor control box passed functional testing. Examination of the airframe and engine revealed no malfunctions that would have prevented normal operation. However, significant saltwater sediment contaminated many hoses and accessories, preventing determination of any pre-impact anomalies.
Weather Conditions
Weather recorded at TMB, 15 miles west of the accident site, at 1353 included a temperature of 80.6°F and a dew point of 55.4°F. These conditions corresponded to the development of carburetor icing at glide power according to a Carburetor Icing Probability Chart.
Maintenance Records
A review of engine maintenance records showed that during the annual inspection completed on August 5, 2023, the right magneto and the crankshaft output seal were replaced. Additionally, the No. 4 cylinder failed the minimum exhaust valve clearance and was reamed per service bulletin (388C) instructions.