# NTSB CEN24LA004: Robinson Helicopter R44, N379SH, Hochatown, OK, October 1, 2023

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Class 3 · Limited · Final report
- Date: October 1, 2023, 12:30 local (17:30 UTC)
- Place: Hochatown, OK
- Coordinates: 34.160278, -94.752222
- Nearby events: https://openairdocs.org/map.md?lat=34.1603&lon=-94.7522&mi=10
- Phase of flight: [Emergency descent](https://openairdocs.org/ntsb-phases/600) (OpenAirDocs' grouping)
- Defining event: [Autorotation: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Central Region
- Parties: Robinson Helicopter Company, FAA - OKC FSDO
- NTSB case key (mKey): 193182
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN24LA004
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/193182/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=193182
- Page: https://openairdocs.org/ntsb/CEN24LA004

## Probable cause

A total loss of engine power during a practice autorotation due to the improper engine idle setting and rigging of the carburetor heat control which resulted in a hard landing.

## Findings

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

- [Ice/rain protection system](https://openairdocs.org/ntsb-findings/01023000): Aircraft › Aircraft systems · Inadequate inspection (probable cause); cases with it: [Robinson Helicopter R44, 1 case](https://openairdocs.org/ntsb-findings/01023000/cases.md?model=7640120), [All aircraft, 4 cases](https://openairdocs.org/ntsb-findings/01023000/cases.md)
- [Performance/control parameters: landing flare](https://openairdocs.org/ntsb-findings/01062041): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Robinson Helicopter R44, 2 cases](https://openairdocs.org/ntsb-findings/01062041/cases.md?model=7640120), [All aircraft, 1,285 cases](https://openairdocs.org/ntsb-findings/01062041/cases.md)
- [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Robinson Helicopter R44, 1 case](https://openairdocs.org/ntsb-findings/02062035/cases.md?model=7640120), [All aircraft, 371 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md)

## Sequence of events

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

- [Autorotation: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Robinson Helicopter R44, 5 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=7640120), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md)
- [Autorotation: Hard landing](https://openairdocs.org/ntsb-events/092); cases with it: [Robinson Helicopter R44, 16 cases](https://openairdocs.org/ntsb-events/092/sequence.md?model=7640120), [All aircraft, 2,102 cases](https://openairdocs.org/ntsb-events/092/sequence.md)

## Analysis

The pilot reported that he was conducting a practice autorotation during a proficiency flight about 400 ft above ground level (agl). As he reduced the engine speed to idle, the engine lost total power. The pilot entered an autorotation and completed a forced landing to a field. The helicopter landed hard and the tailboom was severed by the main rotor blades. Examination of the engine revealed that the idle speed was set below 50 percent, which was below the manufacturer’s recommendation of 60 to 65 percent. Additionally, the carburetor heat control cable was rigged improperly, and therefore, was jammed in the full heat position. The combination of these factors would have likely made the engine more susceptible to losing power, especially with an abrupt power reduction initiated by the pilot during the simulated autorotation. After reviewing the available maintenance records, it is possible the engine idle speed was improperly set, and the carburetor heat control was improperly rigged when the engine was overhauled and installed in the helicopter; however, investigators were unable to establish exactly when the misrigging took place or why it was not noticed during subsequent maintenance.

## Factual narrative

On October 1, 2023, about 1230 central daylight time, a Robinson Helicopter Company R44, N379SH, was substantially damaged when it was involved in an accident near Hochatown, Oklahoma. The pilot was not injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot, who was also a flight instructor, reported that he was conducting a practice autorotation during a proficiency flight about 400 ft agl. As he reduced the engine speed to idle to simulate a loss of engine power, the engine lost total power. The pilot entered an autorotation and completed a forced landing to a field. The helicopter landed hard and the tailboom was severed by the main rotor blades. The pilot exited the helicopter unassisted. The helicopter sustained substantial damage to the tailboom and the main rotor blades. A postaccident examination revealed that the carburetor heat control knob was jammed in the full heat position. Further examination revealed that the carburetor heat control cable was rigged so that the cable was pulled beyond the end of the cable conduit sleeve (figure 1). When the carburetor heat knob was actuated, the control cable would bind with the conduit sleeve. Figure 1: Carburetor heat control cable as found. The cable is free from the conduit sleeve (circled in yellow). Figure 2 shows a normal engagement of the carburetor heat control cable in the conduit sleeve. Figure 2. The normal engagement of the carburetor heat cable and conduit. Cable is inserted into the conduit sleeve (circled in yellow). No other anomalies were found within the rigging or flight controls that would have precluded normal operation. Single contact marks on the fore and aft faces of the upper sheave and adjacent components are consistent with the engine not running at the time of impact. The V-belts and tail boom were cut and removed to facilitate an engine run. The engine started and ran at various power settings. The idle was set to below 50 percent (the typical idle speed without V-belts is 60-65 percent). Robinson Helicopter Company Safety Notices 27 and 38 advise on how to slowly reduce throttle while practicing autorotations. RHC Safey Notice 27 states that during simulated power failures, “throttle should be rolled off smoothly, never ‘chopped.’” A review of the helicopter maintenance records revealed that on August 25, 2022, the engine was overhauled and installed, and an annual inspection of the helicopter was completed. The last 100-hour inspection was completed on August 16, 2023. The helicopter had accumulated 44.2 hours since the 100-hour inspection. Investigators were unable to determine the last time the carburetor control cable was rigged or when the engine idle was set.

## Aircraft

- Registration: [N379SH](https://openairdocs.org/deregistered/N379SH-2024-04-20), registration cancelled 2024-04-20, S/N 2240, built 2012 (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: 2240
- Year built: 2012
- Airframe hours: 241.9
- Engines: Lycoming O-540-F1B5 260 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: Jacasky LLC, doing business as Sky Tours Hochatown
- Registered owner: Spitzer Helicopter LLC
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, August 16, 2023, 44.2 hours before

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 25; injuries: none; commercial, flight instructor; instrument ratings: helicopter; medical: class 2, without waivers/limitations; last flight review September 10, 2023; seat: right; restraint: 3-point; flight hours: 1,353 total, 600 in this make and model, 1,349 as pilot in command, 151 in the last 90 days, 42 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 88 °F, dew point 66 °F
- Altimeter: 30.16 inHg
- Observed at: K4O4, 16 nm away
- METAR: K4O4 011715Z AUTO VRB05KT 10SM CLR 31/19 A3016 RMK AO2

## 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 20231001014119A](https://openairdocs.org/incident/20231001014119A), Oct 1, 2023: Robinson Helicopter R44, Hochatown, OK, Substantial damage. After departing a private heliport in Hochatown, OK the pilot maneuvered the aircraft at 400 feet AGL to practice an auto-rotation maneuver in a field 0.3…

## Docket (8 files)

The files NTSB released with the investigation on November 26, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=193182. 8.3 MB in all.

- Investigation photographs (item 1, PDF, 3 pages, 296 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16601500&FileExtension=pdf&FileName=Photo%20Array-Rel.pdf
- Pilot/operator aircraft accident report, NTSB form 6120.1 (item 2, PDF, 9 pages, 3.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17024930&FileExtension=pdf&FileName=6120_1_Fillable_10-11_Redacted-Rel.pdf
- Examination summary (item 3, PDF, 11 pages, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17018795&FileExtension=pdf&FileName=Examination%20Summary%20N379SH-Rel.pdf
- Statement of party representatives to NTSB investigation (item 4, PDF, 1 page, 84 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17022322&FileExtension=pdf&FileName=Party%20Form%20-%20Robinson_Redacted-Rel.pdf
- Maintenance records (item 5, PDF, 5 pages, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17022864&FileExtension=pdf&FileName=Pages%20from%20N379SH%20Logs_Docket_Redacted-Rel.pdf
- Robinson helicopter safety notice 27 (item 6, PDF, 1 page, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17022215&FileExtension=pdf&FileName=rhc_sn27-Rel.pdf
- Robinson helicopter safety notice 38 (item 7, PDF, 1 page, 167 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17023321&FileExtension=pdf&FileName=rhc_sn38-Rel.pdf
- Release of aircraft wreckage, NTSB form 6120.15 (item 8, PDF, 1 page, 389 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17027071&FileExtension=pdf&FileName=Release-of-Wreckage-N379SH_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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