# NTSB ERA24LA166: Robinson Helicopter R44, N234ZT, Key Biscayne, FL, April 6, 2024 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Class 3 · Limited · Final report - Date: April 6, 2024, 13:50 local (17:50 UTC) - Place: Key Biscayne, FL · Atlantic Ocean - Coordinates: 25.66406, -80.13981 - Nearby events: https://openairdocs.org/map.md?lat=25.6641&lon=-80.1398&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) - Highest injury: Serious injuries - Injuries: 1 serious - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Eastern Region Aviation - Parties: Lycoming Engines, FAA/FSDO, Robinson Helicopter - NTSB case key (mKey): 194041 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA24LA166 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194041/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=194041 - Page: https://openairdocs.org/ntsb/ERA24LA166 ## Probable cause A loss of engine power for reasons that could not be determined. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Robinson Helicopter R44, 11 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=7640120), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) (defining event); cases with it: [Robinson Helicopter R44, 7 cases](https://openairdocs.org/ntsb-events/000/sequence.md?model=7640120), [All aircraft, 1,703 cases](https://openairdocs.org/ntsb-events/000/sequence.md) - [Enroute: Ditching](https://openairdocs.org/ntsb-events/441); cases with it: [Robinson Helicopter R44, 2 cases](https://openairdocs.org/ntsb-events/441/sequence.md?model=7640120), [All aircraft, 186 cases](https://openairdocs.org/ntsb-events/441/sequence.md) ## Analysis About 20 minutes after departure on the over-water flight, the pilot of the helicopter felt two “jerks,” although there were no caution/warning illuminations or aural warnings and the engine gauges were all “in the green.” He turned toward land and descended to 500 ft above the water. The pilot applied carburetor heat, then felt a “shake” and noted that he was having to add power as the helicopter was decelerating. While maneuvering the helicopter as close to land as possible, the low main rotor rpm horn sounded and the pilot described that the engine had lost a significant amount of power. The pilot selected an unoccupied area in the water for an autorotative landing, during which the tailboom separated. He exited the helicopter and was rescued shortly afterward. Postaccident examination of the airframe and engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation of the helicopter or its engine. Additionally, the engine governor control box was tested and it passed all testing parameters. Significant saltwater and sediment contamination prevented the determination of any non-mechanical pre-impact anomalies that may have impacted normal engine operation. Although weather conditions were favorable for carburetor icing at glide power, the pilot stated that he applied carburetor heat during his descent, so carburetor ice was not a likely reason for the loss of engine power. ## Factual narrative On April 6, 2024, about 1350 eastern daylight time, a Robinson R-44, N234ZT, was substantially damaged when it was involved in an accident near Key Biscayne, Florida. The pilot was seriously injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, he topped off the fuel tanks at Miami Executive Airport (TMB), Miami, Florida, completed a preflight inspection, and was flying on a visual-flight-rules (VFR) flight plan with VFR flight following services to North Eleuthera Airport (MYEH), North Eleuthera, Bahamas. About 20 minutes after departure, after leveling off, he felt a millisecond “jerk.” He felt something similar the week before and had attributed it to a thermal or gust. Although there were no caution/warning illuminations or aural warnings, and the engine gauges were all “in the green,” he turned back toward land as a precaution. A minute later, he felt another “jerk.” He descended to 500 ft above ground level while applying carburetor heat. The pilot then felt a longer “shake,” at which time he declared an emergency. He began hearing odd engine sounds and noted that he was having to add power as the helicopter was decelerating. While maneuvering the helicopter as close to land as possible, the pilot started to feel a vibration, the low main rotor rpm horn sounded, and the pilot described that the engine had lost a “significant” amount of power. The pilot began an autorotation, and the helicopter entered the Atlantic Ocean at about 35 kts and about 1 nm from Key Biscayne. The helicopter’s empennage was substantially damaged, and the aft portion of the tail section was impact separated. 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 liquid consistent in color and odor with aviation fuel, some 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 was performed for the main tank per the maintenance manual, and the results were within the acceptable allowance. 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. Postaccident examination of the engine revealed evidence of saltwater and saltwater corrosion. The engine’s crankshaft could not be rotated when attempting to rotate the cooling fan by hand. The crankcase contained about 2 gallons of salt water, and the oil quick drain was obstructed with sludge that had to be removed to drain the oil. The remaining oil was sufficient for engine operation. All six cylinders were removed and examined. The No. 5 cylinder was difficult to remove from the piston, and once freed, a large quantity of blackened salt-like deposits was noted between theNo. 5 cylinder and the cylinder wall. All cylinders had varying amounts of salt deposits and were heavily corroded consistent with submersion in salt water. With the cylinders removed, crankshaft and camshaft continuity was confirmed. Once the cylinder valves were released from the binding of the corrosion and deposits, all exhaust and intake valves were examined and moved freely in their respective valve guide; no scoring, material transfer, or carbon deposits were noted on the shafts of the valves. Salt deposits and corrosion were noted throughout the carburetor consistent with submersion in salt water. The fuel inlet screen was examined and found to have saltwater contamination. Both magnetos were filled with salt deposits and corroded from saltwater immersion. The magnetos were rotated by hand and no spark was noted at any of the ignition towers. The engine governor control box was functionally tested on an engineering test stand and passed all testing parameters. Examination of the airframe and engine revealed no malfunctions that would have prevented normal operation of the helicopter or its engine. Significant saltwater sediment contaminated many hoses and accessories and prevented the determination of any pre-impact anomalies that may have affected normal operation. The 1353 weather recorded at TMB, 15 miles west of the accident site, 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 on a Carburetor Icing Probability Chart. 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, and the No. 4 cylinder failed the minimum exhaust valve clearance and was reamed per the service bulletin (388C) instructions. ## Aircraft - Registration: [N234ZT](https://openairdocs.org/aircraft/N234ZT), registered now, S/N 30027, built 2017 (OpenAirDocs) - Reported make and model: ROBINSON HELICOPTER R44 - Registry model: [Robinson Helicopter R44](https://openairdocs.org/model/robinson-helicopter-r44) (registry code 7640120) (OpenAirDocs) - Registry engine: [Lycoming O-540-F1B5](https://openairdocs.org/engine/lycoming-o-540-f1b5) (registry code 42353, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 30027 - Year built: 2017 - Airframe hours: 550 - Engines: Lycoming O-540-F1B5 210 horsepower turbo shaft - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, July 31, 2023, 456 hours before - Departed: TMB, Miami, FL - Destination: MYEH, North Eleuthera, OF - Flight plan: VFR - Equipment: Electronic primary flight display, Handheld GPS, Onboard weather, ADS-B, Auto-pilot, Electronic multifunction display ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 55; injuries: minor; private; medical: class 3, with waivers/limitations; last flight review June 30, 2023; seat: right; restraint: 3-point; flight hours: 793 total, 725 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 290° at 9 knots, gusting 17 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 81 °F, dew point 55 °F - Altimeter: 30.02 inHg - Observed at: TMB, 16 nm away - METAR: METAR KTMB 061753Z 31008G18KT 10SM CLR 27/13 A3002 RMK AO2 SLP165 6//// T02670128 10272 20156 58014 PNO $= ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20240406004099A](https://openairdocs.org/incident/20240406004099A), Apr 6, 2024: Robinson Helicopter R44, Key Biscayne, FL, Destroyed. Part 91 operation Robinson R44, registration [privacy data omitted] serial number 30027 departing miami executive airport (ktmb) to eleuthera Bahamas, with one… ## Docket (10 files) The files NTSB released with the investigation on January 2, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=194041. 72.1 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 2.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17699076&FileExtension=pdf&FileName=ERA24LA166%20Signed%206120_Redacted-Rel.pdf - Pilot's statements (item 2, PDF, 5 pages, 130 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17737686&FileExtension=pdf&FileName=ERA24LA166%20Pilot%20Statements_Redacted-Rel.pdf - Fuel receipt (item 3, PDF, 1 page, 68 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17699704&FileExtension=pdf&FileName=Fuel%20Receipt_Redacted-Rel.pdf - Maintenance log excerpts (item 4, PDF, 9 pages, 55.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17738490&FileExtension=pdf&FileName=Maintenance%20Log%20Excerpts_Redacted-Rel.pdf - Carburetor icing probability chart (item 5, PDF, 1 page, 325 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17745595&FileExtension=pdf&FileName=ERA24LA166%20Carburetor%20Icing%20Probability%20Chart-Rel.pdf - Investigative photographs (item 6, PDF, 8 pages, 2.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17700344&FileExtension=pdf&FileName=Photo%20Array-Rel.pdf - Airframe and engine examination (item 7, PDF, 36 pages, 7.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17750842&FileExtension=pdf&FileName=ERA24LA166%20Airframe%20and%20Engine%20Examination%20FINAL-Rel.pdf - Memorandum of record governor examination (item 8, PDF, 1 page, 71 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17744321&FileExtension=pdf&FileName=ERA24LA166%20Memorandum%20of%20Record%20-%20Governor%20Controller%20Exam-Rel.pdf - Statement of party representatives to NTSB investigation (item 9, PDF, 15 pages, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17700474&FileExtension=pdf&FileName=Party%20Forms_Redacted-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 10, PDF, 2 pages, 2.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17700956&FileExtension=pdf&FileName=ERA24LA166%20Signed%20Final%20Wreckage%20Release_Redacted-Rel.pdf From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.