# NTSB CEN24LA358: Hughes 369, N8969F, Canton, MI, September 11, 2024

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Class 3 · Limited · Final report
- Date: September 11, 2024, 14:00 local (18:00 UTC)
- Place: Canton, MI · Off airport landing zone.
- Coordinates: 42.311235, -83.464731 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=42.3112&lon=-83.4647&mi=10
- Phase of flight: [Prior to flight](https://openairdocs.org/ntsb-phases/100) (OpenAirDocs' grouping)
- Defining event: [Prior to flight: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report September 10, 2026
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Central Region
- Parties: MD Helicopters, FAA East Michigan FSDO
- ADs cited in the narratives: [AD 2005-21-02](https://openairdocs.org/ad/2005-21-02) (OpenAirDocs)
- NTSB case key (mKey): 195126
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN24LA358
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/195126/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=195126
- Page: https://openairdocs.org/ntsb/CEN24LA358

## Probable cause

Fatigue cracking of the main rotor blade that occurred at an undetermined time.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Main rotor system: main rotor blade system](https://openairdocs.org/ntsb-findings/01046210): Aircraft › Aircraft propeller/rotor · Failure (probable cause); cases with it: [Hughes Helicopters HUGHES 369D, 6 cases](https://openairdocs.org/ntsb-findings/01046210/cases.md?model=4470706), [All aircraft, 60 cases](https://openairdocs.org/ntsb-findings/01046210/cases.md)
- [Main rotor system: main rotor blade system](https://openairdocs.org/ntsb-findings/01046210): Aircraft › Aircraft propeller/rotor · Damaged/degraded (probable cause); cases with it: [Hughes Helicopters HUGHES 369D, 6 cases](https://openairdocs.org/ntsb-findings/01046210/cases.md?model=4470706), [All aircraft, 60 cases](https://openairdocs.org/ntsb-findings/01046210/cases.md)
- [Record-keeping: aircraft/maintenance logs](https://openairdocs.org/ntsb-findings/02062515): Personnel issues › Task performance · Maintenance personnel; cases with it: [Hughes Helicopters HUGHES 369D, 1 case](https://openairdocs.org/ntsb-findings/02062515/cases.md?model=4470706), [All aircraft, 21 cases](https://openairdocs.org/ntsb-findings/02062515/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Prior to flight: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Hughes Helicopters HUGHES 369D, 4 cases](https://openairdocs.org/ntsb-events/330/sequence.md?model=4470706), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md)
- [Maneuvering-low-alt flying: External load event (Rotorcraft)](https://openairdocs.org/ntsb-events/480); cases with it: [Hughes Helicopters HUGHES 369D, 9 cases](https://openairdocs.org/ntsb-events/480/sequence.md?model=4470706), [All aircraft, 51 cases](https://openairdocs.org/ntsb-events/480/sequence.md)
- [Maneuvering-low-alt flying: Attempted remediation/recovery](https://openairdocs.org/ntsb-events/060); cases with it: [Hughes Helicopters HUGHES 369D, 3 cases](https://openairdocs.org/ntsb-events/060/sequence.md?model=4470706), [All aircraft, 1,422 cases](https://openairdocs.org/ntsb-events/060/sequence.md)
- [Landing: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Hughes Helicopters HUGHES 369D, 9 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=4470706), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md)

## Analysis

The pilot of the helicopter was performing external lift operations when he noticed an “intermittent and unusual vibration.” The pilot performed a precautionary landing, and a postflight inspection of the main rotor system revealed a crack in one main rotor blade, which constituted substantial damage to the helicopter. Postaccident examination of the main rotor blade revealed that a large crack extended from the leading edge spar on the lower surface to the middle of the main rotor blade along the doubler leading edge on the upper surface of the blade. There was an area of chipped paint adjacent to the crack at the outboard tip of the root fitting on the lower side of the blade. After sectioning, the large crack was mechanically exposed and examined stereoscopically. Feathery features consistent with fatigue were observed on the lower side fracture surfaces of the doubler, skin, and spar. Scanning electron microscope examination revealed numerous ratchet marks at the doubler-skin and skin-spar interfaces emanating at the outboard sides of both layers, consistent with multiple initiation fatigue starting from the outboard side. Dark-colored deposits were observed on the spar fracture surface at the tip and on the adjacent skin fracture surface due to the rubbing of mating fracture surfaces. The large size of the crack and the rubbing of the mating fracture surfaces was consistent with fatigue crack growth over an extended period of time. The accident helicopter main rotor blades were subject to an FAA Airworthiness Directive (AD) for regular inspections due to the helicopter’s use for external lift operations. The cracked main rotor blade was installed onto the accident helicopter the month before the accident and had accrued about 67 hours of operation since installation. The operator reported that an inspection in accordance with the AD (AD 2005-21-02) was most recently performed 6 days (12.4 flight hours) before the accident. Maintenance personnel noted no defects during recent inspections. According to the operator, the inboard portion of the main rotor blade was painted gloss white by the operator’s director of maintenance sometime during the month of the accident; however, there were no maintenance records reflecting when or by whom the painting was performed or inspected. It is likely that the fatigue crack occurred sometime between when the main rotor blade was installed onto the helicopter and before the accident flight; however, when the fatigue crack occurred could not be determined. Manufacturer guidance stated that the identification of cracks in main rotor blades requires a careful examination, including the use of supplemental lighting and optical magnification. Whether maintenance personnel performed the inspections with adequate lighting and magnification was not determined. Additionally, it could not be determined whether the fatigue cracking may have been concealed by the recent painting of the main rotor blade.

## Factual narrative

On September 11, 2024, about 1400 eastern daylight time, a Hughes 369D helicopter, N8969F, sustained substantial damage when it was involved in an accident near Canton, Michigan. The pilot was uninjured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 133 rotorcraft external load flight. The operator used the helicopter for external lift operations. The purpose of the low-level flight was to support powerline maintenance work. The helicopter was operating from an off-airport landing zone delivering cargo to a powerline structure about 300 yards away. While in flight, the pilot, who was sitting in the left seat, noticed an “intermittent and unusual vibration.” The pilot performed a precautionary landing and shut down the helicopter without further incident. The pilot performed a visual inspection of the main rotor system, and he observed a crack in the yellow main rotor blade (main rotor blades are typically marked with various colors to easily identify and reference each individual blade). The helicopter sustained substantial damage to the yellow main rotor blade. There was no further damage to the helicopter. The main rotor blade was manufactured by MD Helicopters (part number 369D21100-523 and serial number 009999-K364) and was subject to a finite life limit of 4,000 total hours. The blade was installed on the helicopter on August 3, 2024, at 3,222.2 total hours. At the time of the accident, the main rotor blade had accumulated 3,289.9 total hours, 67.7 hours since installation, and 6 days (12.4 hours) since the most recent inspection. Postaccident examination of the main rotor blade revealed that a large crack extended from the leading edge spar on the lower surface to the middle of the main rotor blade along the doubler leading edge on the upper surface. There was an area of chipped paint adjacent to the crack at the outboard tip of the root fitting on the lower side of the main rotor blade. After sectioning, the large crack in the main rotor blade was mechanically exposed and examined stereoscopically. Feathery features were observed on the lower side fracture surfaces of the doubler, skin, and spar. Scanning electron microscope examination revealed numerous ratchet marks at the doubler-skin and skin-spar interfaces emanating at the outboard sides of both layers. Dark-colored deposits were observed on the spar fracture surface at the tip and on the adjacent skin fracture surface. On February 4, 2004, MD Helicopters released Service Bulletin (SB) 369D-201R2, Main Rotor Blade Assembly Torque Event Inspection, which they classified as mandatory compliance. The SB stated that some operators had experienced cracking of the main rotor blades, and that the cracked blades were associated with a high number of torque events (TE), or external lifts per hour. The SB provided procedures for operators to determine the number of TEs accumulated on each main rotor blade in order to establish inspection intervals. The contents ofthis SB were later adopted into FAA Airworthiness Directive (AD) 2005-21-02 on November 1, 2005, in which the FAA required compliance with the service bulletin and recurring inspections of the main rotor blades at intervals not to exceed 200 TEs or 35 hours time in service, whichever occurs first. MD Helicopters CSP-HMI-2, Handbook of Maintenance Instructions – Servicing and Maintenance, which is applicable to the 369 series, defines TE as “the transition to a hover from forward flight” or “any external lift operation.” The accident main rotor blade part number was subject to this AD. The inspection procedures listed for maintenance personnel in AD 2005-21-02 specifically describe the inspection for chordwise cracks protruding from the underside of the root fitting and the doubler (the location and type of cracking found on the accident main rotor blade). The inspection procedures also specify using a bright light and a 10x magnification glass for the inspection of the lower side of the main rotor blades. MD Helicopters CSP-HMI-2, Handbook of Maintenance Instructions – Servicing and Maintenance, contains additional guidance for maintenance personnel performing a visual inspection. During a TE inspection, the main rotor blade should be lifted off of the droop stop from the outboard end of the blade. The handbook stated that the bottom side of main rotor blades are more susceptible to cracks. The guidance also contains a caution for TE inspections and states in part that, “A crack can be difficult to find if a bright light is not used.” According to the operator, the inboard portion of the main rotor blade was painted gloss white by the operator’s director of maintenance sometime in September 2024; however, there were no maintenance records available showing the paint work that was performed, when the paintwork was exactly performed, who performed the paint work, and who inspected the paint work. Instructions contained in MD Helicopters CSP-HMI-2 stated: It is recommended to only paint the inboard 24 inch (60.96 cm) gloss white to help with crack detection. All blades must be painted the same. The operator’s maintenance records revealed that a TE inspection in compliance with FAA AD 2005-21-02 was most recently performed on September 5, 2024, at a helicopter total time of 18,306.4 hours and TE of 83,119. Since the main rotor blade was installed, four compliance entries with FAA AD 2005-21-02 were found in the operator’s maintenance records, with three different company mechanics performing that work. All four compliance entries contained a note stating, “no defects.” The MD Helicopters MD 500D (Model 369D) Rotorcraft Flight Manual (RFM) discusses preflight inspection procedures and states, in part, for the pilot to check: Main rotor blades for chordwise cracks on the underside of the blade skin and doubler. If existing, the cracks will be at the leading and trailing edges of the root fitting in the area of the two most outboard bolts or outermostend of the lower root fitting. The RFM does not require the use of supplemental lighting, such as a flashlight, during the preflight inspection. The RFM contains an emergency procedure for abnormal vibrations and lists the indications as, “sudden, unusual, or excessive vibrations occurring during flight.” The manual states that the onset of unusual or excessive vibrations in the helicopter may be an indication of problems in the rotor drive or drive train systems, and that the pilot should land as soon as possible to have the cause of vibration identified and corrected before any further flights. On October 2, 2024, MD Helicopters released Service Letter (SL) 369D-144, Inspection of the Main Rotor Blades Assemblies. The SL recommends that owners and operators ensure that inspections per MD Helicopters Service Bulletin 369D-201R2 are completed and FAA AD 2005-21-02 are referenced. The document further states in part: Failure to comply with the bulletin can cause the loss of a main rotor blade during operation and cause significant vibrations and a loss of helicopter control.

## Aircraft

- Registration: [N8969F](https://openairdocs.org/aircraft/N8969F), registered now, S/N 980344-D, built 1978 (OpenAirDocs)
- Reported make and model: HUGHES 369 (D)
- Registry model: [Hughes Helicopters HUGHES 369D](https://openairdocs.org/model/hughes-helicopters-hughes-369d) (registry code 4470706) (OpenAirDocs)
- Registry engine: [Rolls-Royce 250-C20B](https://openairdocs.org/engine/rolls-royce-250-c20b) (registry code 54385, turbo-shaft) (OpenAirDocs)
- Category: Helicopter
- Serial number: 980344-D
- Year built: 1978
- Airframe hours: 18318.8
- Engines: Rolls-Royce 250-C20B 420 horsepower turbo shaft
- Damage: Substantial damage
- Flight: External load, Part 133
- Operator: Helicopter Powerline Services, LLC, doing business as Helicopter Powerline Services
- Registered owner: TeryJon Aviation, Inc.
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, August 3, 2024, 67.7 hours before
- Departed: ARB, Ann Arbor, MI
- Destination: ARB, Ann Arbor, MI
- Equipment: Handheld GPS

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 50; injuries: none; private, commercial, flight instructor; airplane ratings: single-engine land; instrument ratings: airplane, helicopter; medical: class 2, without waivers/limitations; last flight review March 24, 2024; seat: left; restraint: 4-point; flight hours: 10,500 total, 10,300 as pilot in command, 75 in the last 90 days, 30 in the last 30 days, 6 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 200° at 4 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 82 °F, dew point 59 °F
- Altimeter: 30.14 inHg
- Observed at: KYIP, 5 nm away
- METAR: KYIP 111753Z AUTO 20004KT 10SM CLR 28/15 A3014 RMK AO2 SLP200 6//// T02780150 58012 $

## 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 20240911014569A](https://openairdocs.org/incident/20240911014569A), Sep 11, 2024: Hughes 369D, Canton, MI, Substantial damage. The aircraft was being flown in support of powerline maintenance work operating from an off airport landing zone and conducting part 133 class b cargo…

## Docket (15 files)

The files NTSB released with the investigation on September 10, 2026, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=195126. 62.8 MB in all.

- Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 10 pages, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20837334&FileExtension=pdf&FileName=CEN24LA358%20NTSB%20Form%206120_1_Redacted-Rel.pdf
- Investigation photographs (item 2, PDF, 5 pages, 910 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20721368&FileExtension=pdf&FileName=Investigation%20Photographs-Rel.pdf
- N8969F - main rotor blade damage video (.mov file) (item 3, MOV, 2.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20719778&FileExtension=MOV&FileName=N8969F%20MRB%20Damage%20Video-Rel.MOV
- NTSB materials laboratory - factual report (item 4, PDF, 38 pages, 23.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19533848&FileExtension=pdf&FileName=25-073%20Materials%20Laboratory%20Factual%20Report%20(CEN24LA358)-Rel.pdf
- Federal aviation administration - airworthiness directive 2005-21-02 (item 5, PDF, 10 pages, 54 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20708584&FileExtension=pdf&FileName=FAA%20AD%202005-21-02_Redacted-Rel.pdf
- MD helicopters - MD500D rotorcraft flight manual excerpts (item 6, PDF, 5 pages, 2.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20709819&FileExtension=pdf&FileName=MD%20MD500D%20RFM%20Excerpts-Rel.pdf
- MD helicopters - 369 series maintenance manual excerpts (item 7, PDF, 12 pages, 1.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20740888&FileExtension=pdf&FileName=MD%20Helicopters%20Maintenance%20Manual%20Excerpts-Rel.pdf
- MD helicopters - service bulletin 369D-201R2 (item 8, PDF, 4 pages, 125 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20708759&FileExtension=pdf&FileName=MD%20Helicopters%20SB369D-201R2-Rel.pdf
- MD helicopters - service letter 369D-144 (item 9, PDF, 2 pages, 62 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20709546&FileExtension=pdf&FileName=MD%20Helicopters%20SL369D-144-Rel.pdf
- Helicopter powerline services - chief executive officer memorandum (item 10, PDF, 1 page, 97 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20734229&FileExtension=pdf&FileName=CEN24LA358%20CEO%20MOR_Redacted-Rel.pdf
- Helicopter powerline services - recent flight logs (item 11, PDF, 2 pages, 12.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20726311&FileExtension=pdf&FileName=Operator%20Recent%20Flight%20Logs_Redacted-Rel.pdf
- Helicopter powerline services - recent maintenance records (item 12, PDF, 2 pages, 5.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20726456&FileExtension=pdf&FileName=Operator%20Recent%20Maintenance%20Records_Redacted-Rel.pdf
- Helicopter powerline services - FAA airworthiness directive 2005-21-02 compliance log (item 13, PDF, 2 pages, 11.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20726731&FileExtension=pdf&FileName=Operator%20AD%20Compliance%20Log_Redacted-Rel.pdf
- Helicopter powerline services - main rotor blade log (item 14, PDF, 1 page, 243 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20726446&FileExtension=pdf&FileName=Operator%20Component%20Log-Rel.pdf
- Statement of party representatives to NTSB investigation (item 15, PDF, 1 page, 236 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20721040&FileExtension=pdf&FileName=NTSB%20Party%20Member%20Form%20-%20MD%20Helicopters_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.

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