# NTSB ERA23LA293: Hughes 369D, N5027P, Waldorf, MD, July 9, 2023 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: July 9, 2023, 10:27 local (14:27 UTC) - Place: Waldorf, MD - Coordinates: 38.6175, -77.001111 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=38.6175&lon=-77.0011&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: Minor injuries - Injuries: 3 minor - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Eastern Region Aviation - Parties: FAA FSDO, MD Helicopters, Rolls-Royce, Haverfield Aviation - ADs cited in the narratives: [AD 90-19-02](https://openairdocs.org/ad/90-19-02) (OpenAirDocs) - NTSB case key (mKey): 192563 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA23LA293 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/192563/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=192563 - Page: https://openairdocs.org/ntsb/ERA23LA293 ## Probable cause Fatigue failure of the overrunning clutch outer race and a subsequent inflight loss of power due to abnormal bending loads as a result of improper reassembly of the clutch subassembly following maintenance and the presence of microcracks on the clutch’s outer race. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Main rotor drive: engine/transmission coupling](https://openairdocs.org/ntsb-findings/01046310): Aircraft › Aircraft propeller/rotor · Fatigue/wear/corrosion (probable cause); cases with it: [Hughes Helicopters HUGHES 369D, 2 cases](https://openairdocs.org/ntsb-findings/01046310/cases.md?model=4470706), [All aircraft, 24 cases](https://openairdocs.org/ntsb-findings/01046310/cases.md) - [Maintenance: scheduled/routine maintenance](https://openairdocs.org/ntsb-findings/02062010): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Hughes Helicopters HUGHES 369D, 1 case](https://openairdocs.org/ntsb-findings/02062010/cases.md?model=4470706), [All aircraft, 320 cases](https://openairdocs.org/ntsb-findings/02062010/cases.md) - [Manufacture/production: equipment manufacture](https://openairdocs.org/ntsb-findings/04013010): Organizational issues › Development · Manufacturer (probable cause); cases with it: [Hughes Helicopters HUGHES 369D, 1 case](https://openairdocs.org/ntsb-findings/04013010/cases.md?model=4470706), [All aircraft, 36 cases](https://openairdocs.org/ntsb-findings/04013010/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [Hughes Helicopters HUGHES 369D, 1 case](https://openairdocs.org/ntsb-events/340/sequence.md?model=4470706), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) ## Analysis The flight crew of the helicopter detected an abnormal noise while in cruise flight and the pilot felt a vibration in the collective. The crew chose to discontinue the mission and return to the departure airport; however, about 4 nautical miles from the airport, there was a loud bang/pop noise and the helicopter yawed left. The pilot entered an autorotation and selected a forced landing site adjacent to a pond in a residential area. Home security video captured the final seconds of the flight. The sounds of the helicopter’s engine and the turning main rotor could be heard before the helicopter appeared in the frame, descending steeply in a level attitude. The helicopter dropped from sight behind a house and reappeared just as the helicopter’s nose flared upward and the tail rotor impacted the surface of the pond about the same time. The tailboom was separated by the turning main rotor at or about water contact. The helicopter’s skids impacted the fence that bordered the pond, and the helicopter subsequently came to rest upright. The engine, which continued to run briefly, was shut down by the pilot and the damaged main rotor blades stopped turning. The crewmembers egressed the helicopter without assistance. Examination of the helicopter revealed the overrunning clutch outer race’s splined shaft had fractured, which disconnected engine power from the main transmission. Examination of the fracture surface showed signatures consistent with fatigue. The examination of the disassembled clutch subassembly revealed off-axis and asymmetric wear, indicating that the overrunning clutch was likely reassembled improperly after its last inspection, which occurred about three months and 22 flight hours before the accident. Additionally, secondary microcracks were observed on the shaft portion of the clutch outer race's splined shaft that likely occurred during its manufacture. The improper reassembly of the clutch subassembly following the inspection likely resulted in abnormal loading of the clutch outer race shaft during operation. This abnormal loading, in addition to the preexisting microcracks, initiated fatigue cracking of the clutch outer race, resulting in its failure during the accident flight. ## Factual narrative On July 9, 2023, at 1027 eastern daylight time, a Hughes 369D helicopter, N5027P, was substantially damaged when it was involved in an accident near Waldorf, Maryland. The commercial pilot and two observer crewmembers sustained minor injuries. The helicopter was operated by Haverfield Aviation, Inc., as a Title 14 Code of Federal Regulations Part 91 powerline inspection flight. The flight crew reported that they planned to complete one flight before forecast weather moved into the area. The pre-mission risk assessment, preflight inspection of the helicopter, and inflight power-assurance check were all satisfactory and the helicopter performed “without incident” for two hours before the crewmember in the back of the helicopter reported hearing an “abnormal noise.” The crewmembers concurred that they heard something “suspicious,” but agreed that it was so subtle they couldn’t decide whether the noise was “abnormal;” however, the pilot reported that he “felt a vibration in the collective” control, and the crew agreed to return to Maryland Airport (2W5), Indian Head, Maryland, where the flight had originated. According to the flight crew, about 4 nautical miles from the departure airport, there was a “loud bang or pop noise and a hard left yaw.” The pilot entered an autorotation and selected a forced landing site adjacent to a pond in a residential area. Company GPS track data depicted the helicopter in cruise flight about 900 ft mean sea level and 100 knots groundspeed for about 8 minutes on a southwesterly heading toward 2W5. The data indicated that the helicopter entered a steep, descending left turn through about 180° before the track data ended at 0 knots about ground level in the vicinity of the accident site. Home security video captured the final seconds of the flight. The sounds of the helicopter’s engine and the turning main rotor could be heard before the helicopter appeared in the frame, descending steeply in a level attitude. The helicopter dropped from sight behind a house and reappeared just as the helicopter’s nose flared upward and the tail rotor impacted the surface of the pond about the same time. The tailboom was separated by the turning main rotor at or about water contact. The helicopter’s skids impacted the fence that bordered the pond, and the helicopter subsequently came to rest upright. The engine, which continued to run briefly, was shut down by the pilot and the damaged main rotor blades stopped turning. The crewmembers egressed the helicopter without assistance. The helicopter was manufactured in 1981 and was powered by a Rolls-Royce 250-C20B turboshaft, 420-horsepower engine. The helicopter’s most recent 100-hour inspection was completed on June 7, 2023, at 24,799.4 total aircraft hours, and included an inspection of the overrunning clutch for oil leakage, correct operation of the clutch, and regreasing of the clutch splines. These overrunning clutch inspections were signed off with no discrepancies noted. Thehelicopter came to rest upright straddling the damaged fence. The cockpit and cabin area appeared intact. The transmission, main rotor mast, and main rotor head all appeared intact and secure in their mounts. Two of the five main rotor blades displayed significant impact damage, and all five blades were secure in their hubs. The tailboom was severed just aft of its mount; the damage was consistent with main rotor contact and impact with water and terrain. A fractured tail rotor gearbox with the tail rotor attached was found separated from the tailboom. One tail rotor blade was severed near its grip. A detailed examination of the helicopter revealed that the overrunning clutch outer race’s splined shaft had fractured. Figure 1. A cutaway view showing the internal components of the overrunning clutch assembly. The input drive (right side) is driven by the engine. The output drive (left side) provides drive to the engine-to-transmission (Kaflex) driveshaft. (Image courtesy of MD Helicopters) An overrunning clutch permits the output, or driven member, of the clutch to freewheel whenever the input, or driving member, is stopped or is rotating at a slower speed. In a helicopter transmission, overrunning clutches are used to disengage the engines from the rotor, allowing the rotors to turn without engine drive. In multiple-engine aircraft, the overrunning clutch permits individual engines to be started without rotating the remaining engines. Safe landings may be executed by autorotation without the use of engines because the overrunning clutch automatically disconnects the engines from the rotor head when the engines are stopped. The overrunning clutch subassembly on the accident helicopter comprised the outer race, inner race, sprag assembly, forward and aft sprag bearings and the output bearing. Adding the clutch housing and retaining ring to the clutch subassembly creates the overrunning clutch assembly. The accident helicopter make and model, when equipped with a hook for external load operations, was subject to FAA Airworthiness Directive (AD) 90-19-02. The AD required disassembly of the overrunning clutch assembly to inspect the condition of the clutch inner race, clutch outer race, and sprag assembly at 300-hour intervals, with replacement of the sprag assembly at 1,800 hours time since new (TSN). The accident overrunning clutch assembly was removed from another helicopter in February 2023 in order to complete the AD inspection. The inspection was completed in April 2023 and the overrunning clutch assembly was installed on the accident helicopter in June 2023, with 1,199.4 hours TSN on the sprag assembly. At the time of the accident, the overrunning clutch had accumulated 22 hours time in service since the AD inspection. The overrunning clutch assembly was examined by the NTSB Materials Laboratory in Washington, DC. Examination of the fracture surface showed signatures consistent with fatigue. Other notable findings included evidence of a gapbetween the forward-most bearing’s inner race and the clutch inner race shoulder, off-axis sprag contact marks around the circumference of the outer race, and asymmetric contact marks on the wave washer. Additionally, secondary microcracks were observed on the shaft portion of the clutch outer race. Closer examination of the microcracks revealed that the black oxide layer on the surface of the clutch outer race that had been applied during the manufacturing process appeared to continue onto the microcrack surfaces in the first grain. For additional details of the clutch assembly examination, see NTSB Materials Laboratory Report No. 24-030 in the docket for this investigation. ## Aircraft - Registration: [N5027P](https://openairdocs.org/aircraft/N5027P), registered now, S/N 611002D, built 1981 (OpenAirDocs) - Reported make and model: HUGHES 369D - Registry model: [Hughes Helicopters HUGHES 369D](https://openairdocs.org/model/hughes-helicopters-hughes-369d) (registry code 4470706) (OpenAirDocs) - Registry engine: [Allison 250-C20B](https://openairdocs.org/engine/allison-250-c20b) (registry code 03081, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 611002D - Year built: 1981 - Airframe hours: 24799.3 - Engines: Rolls Royce 250-C20B 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Aerial observation, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, June 7, 2023, 116.1 hours before - Departed: 2W5, Indian Head, MD - Flight plan: Company VFR - Airport: None - Equipment: Satellite tracking device, ADS-B, Handheld GPS ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 50; injuries: minor; commercial; instrument ratings: helicopter; medical: class 2, without waivers/limitations; last flight review February 19, 2022; seat: left; restraint: 4-point; flight hours: 2,012 total, 1,094 in this make and model, 1,954 as pilot in command, 69 in the last 90 days, 18 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 88 °F, dew point 73 °F - Altimeter: 29.84 inHg - Observed at: KDAA, 10 nm away - METAR: KDAA 081655Z AUTO 00000KT 10SM CLR 31/23 A2984 RMK AO2 SLP107 T03080229 $ ## 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 20230709009939A](https://openairdocs.org/incident/20230709009939A), Jul 9, 2023: Hughes 369D, Waldorf, MD, Substantial damage. Pilot was in cruise flight recovering from power line survey commercial flight to indian head, MD (2W5), due to incoming weather system. Approximately 6 mi se… ## Other investigations on N5027P (1) 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. - [NTSB BFO94LA155](https://openairdocs.org/ntsb/BFO94LA155), Aug 28, 1994: Hughes 369D (N5027P), Butler, PA, substantial damage. Probable cause: The malfunction of the emergency fuel vent and the exhaustion of the fuel supply which resulted in the loss of engine power. ## Docket (16 files) The files NTSB released with the investigation on June 4, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=192563. 120 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 5.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18373252&FileExtension=pdf&FileName=6120_N5027P%20f_print_Redacted-Rel.pdf - Crewmember statements (item 2, PDF, 2 pages, 123 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18375429&FileExtension=pdf&FileName=N5027P%20Crewmember%20Statements-Rel.pdf - GPS - specialista��s factual report (item 3, PDF, 7 pages, 4 photos, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16241415&FileExtension=pdf&FileName=Global%20Positioning%20System%20Device%20-%20Specialist%27s%20Factual-Rel.pdf - GPS - specialist's factual - attachment 1 - tabular data (item 4, CSV, 40 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16241425&FileExtension=csv&FileName=Global%20Positioning%20System%20Device%20-%20Specialist%27s%20Factual%20-%20Attachment%201%20-%20Tabular%20Data-Rel.csv - Materials laboratory factual report 24-030 (item 5, PDF, 35 pages, 50 photos, 11.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17388035&FileExtension=pdf&FileName=24-030-Rel.pdf - Helicopter specialist's factual report (item 6, PDF, 10 pages, 4 photos, 508 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17414067&FileExtension=pdf&FileName=Helicopter%20Specialist%27s%20Factual%20Report%20(ERA23LA293)-Rel.pdf - Helicopter specialist's factual report - attachment 1 (item 7, PDF, 2 pages, 864 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17413576&FileExtension=pdf&FileName=Helicopter%20Specialist%27s%20Factual%20Report%20-%20Attachment%201_Redacted%20(ERA23LA293)-Rel.pdf - Helicopter specialist's factual report - attachment 2 (item 8, PDF, 2 pages, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17414077&FileExtension=pdf&FileName=Helicopter%20Specialist%27s%20Factual%20Report%20-%20Attachment%202_Redacted%20(ERA23LA293)-Rel.pdf - Helicopter specialist's factual report - attachment 3 (item 9, PDF, 2 pages, 333 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17414271&FileExtension=pdf&FileName=Helicopter%20Specialist%27s%20Factual%20Report%20-%20Attachment%203%20(ERA23LA293)-Rel.pdf - Helicopter specialist's factual report - attachment 4 (item 10, PDF, 3 pages, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17414330&FileExtension=pdf&FileName=Helicopter%20Specialist%27s%20Factual%20Report%20-%20Attachment%204_Redacted%20(ERA23LA293)-Rel.pdf - Materials laboratory factual report 24-039 (item 11, PDF, 4 pages, 1 photo, 337 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17440135&FileExtension=pdf&FileName=24-039-Rel.pdf - Video study (item 12, PDF, 8 pages, 489 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18128660&FileExtension=pdf&FileName=Waldorf_Video_Study_final-Rel.pdf - Video file (item 13, MOV, 89.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18241964&FileExtension=mov&FileName=5027P%20Video-Rel.mov - Photo array (item 14, PDF, 3 pages, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18376887&FileExtension=pdf&FileName=ERA23LA293%20Photo%20Array-Rel.pdf - Statement of party representatives to NTSB investigation (item 15, PDF, 16 pages, 4.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18375928&FileExtension=pdf&FileName=ERA23LA293%20Signed%20Party%20Forms_Redacted-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 16, PDF, 1 page, 122 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18376147&FileExtension=pdf&FileName=Release%20of%20Aircraft%20Wreckage_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.