# NTSB CEN17LA375: Hiller UH 12A, N2686, Griffith, IN, September 11, 2017

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: September 11, 2017, 11:00 local (16:00 UTC)
- Place: Griffith, IN
- Coordinates: 41.519721, -87.399444 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=41.5197&lon=-87.3994&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Defining event: [Maneuvering: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report July 8, 2019
- Report: Approved by Office Director
- NTSB office: Central Region
- Parties: FAA FSDO
- NTSB case key (mKey): 96231
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN17LA375
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/96231/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=96231
- Page: https://openairdocs.org/ntsb/CEN17LA375

## Probable cause

The loss of tail rotor thrust due to a failed tail rotor driveshaft, which resulted in a loss of tail rotor control and a hard landing.

## Findings

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

- [Tail rotor drive system: tail rotor drive shaft](https://openairdocs.org/ntsb-findings/01046510): Aircraft › Aircraft propeller/rotor · Failure (probable cause); cases with it: [Hiller UH-12A, 1 case](https://openairdocs.org/ntsb-findings/01046510/cases.md?model=4360104), [All aircraft, 25 cases](https://openairdocs.org/ntsb-findings/01046510/cases.md)

## Sequence of events

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

- [Maneuvering: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) (defining event); cases with it: [Hiller UH-12A, 1 case](https://openairdocs.org/ntsb-events/333/sequence.md?model=4360104), [All aircraft, 410 cases](https://openairdocs.org/ntsb-events/333/sequence.md)
- [Maneuvering: Loss of control in flight](https://openairdocs.org/ntsb-events/240); cases with it: [Hiller UH-12A, 3 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=4360104), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md)
- [Maneuvering: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Hiller UH-12A, 2 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=4360104), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md)

## Analysis

The flight instructor was providing dual flight instruction to a student pilot in the helicopter. About 10 minutes into the flight, while in a 3-5 ft hover, the student began to lose helicopter control and the helicopter began to spin to the right. Because the student could not regain control, the instructor took the controls, but the helicopter did not respond to cyclic inputs and left pedal input. At this point, the instructor assumed there was a loss of thrust from the tail rotor. He rolled the throttle off, and the helicopter settled to the ground and landed hard. After the landing, the instructor observed that the tail rotor and tail rotor driveshaft were not spinning and heard a grinding noise near the connection of the transmission output shaft and the tail rotor driveshaft. The instructor found that the tail rotor guard had broken off the helicopter and was about 20 ft away. The instructor could not recall if or when the tail rotor guard struck the ground. Examination of the helicopter revealed that the tail rotor driveshaft had failed near the output shaft of the tail rotor drive assembly. Substantial damage was incurred to the tail rotor and tailboom. Maintenance records were not available. Because neither the student nor the instructor could regain helicopter control, it is likely that the tail rotor driveshaft failed in flight, which led to the loss of tail rotor thrust and subsequent loss of tail rotor control.

## Factual narrative

On September 11, 2017, about 1100 central daylight time, a Hiller UH-12A helicopter, N2686, registered to a private individual, sustained substantial damage after a loss of directional control and collision with the ground following a loss of the tail rotor drive in the vicinity of Griffith, Indiana. The certified helicopter flight instructor (CFI) and his student were not injured. Visual meteorological conditions prevailed throughout the area and no flight plane was filed. The local instructional flight was being conducted under the provisions of Federal Code of Regulations Part 91. The fight originated at 1050 from the Griffith-Merriillville Airport (O5C), Griffith, Indiana. The CFI stated that he was providing dual flight instruction to a student pilot. About 10 minutes into the flight, while in a 3-5 foot hover, the student began to lose control and the helicopter began to spin to the right. As the student could not regain control, the CFI took the controls. Upon taking the controls, the helicopter was not responding to cyclic inputs and left pedal input. At this point, the CFI assumed a loss of thrust from the tail rotor. He rolled the throttle off and the helicopter settled to the ground and landed hard. After asking if his student was ok, the CFI exited the helicopter while the main rotor was still spinning. He observed the tail rotor and tail rotor drive shaft were not spinning and could hear a grinding noise near the connection of the transmission output shaft and the tail rotor drive shaft. After the main rotor stopped spinning, the CFI found the tail rotor guard had broken off the helicopter and was laying about 20-feet away. The CFI did not recall if or when the tail rotor guard struck the ground. The helicopter was towed to a hangar and was inspected by a local mechanic and FAA inspector. During the inspection, it was discovered that the tail rotor driveshaft had failed near the output shaft of the tail rotor drive assembly. Substantial damage was incurred to the tail rotor and tail boom. Maintenance records were not available.

## Aircraft

- Registration: [N2686](https://openairdocs.org/deregistered/N2686-2020-01-31), registration cancelled 2020-01-31, S/N 168 (OpenAirDocs)
- Reported make and model: HILLER UH 12A (NO SERIES)
- Registry model: [Hiller UH-12A](https://openairdocs.org/model/hiller-uh-12a) (registry code 4360104) (OpenAirDocs)
- Registry engine: [Franklin 6V 350 series](https://openairdocs.org/engine/franklin-6v-350-series) (registry code 27043, reciprocating) (OpenAirDocs)
- Category: Helicopter
- Serial number: 168
- Year built: 1950
- Airframe hours: 2653.8
- Engines: Franklin 6V350 200 horsepower reciprocating
- Damage: Substantial damage
- Flight: Instructional, Part 91
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, September 1, 2017, 49 hours before
- Departed: 05C, Griffith, IN
- Destination: 05C, Griffith, IN
- Airport: 05C, Griffith-Merriville Airport
- Equipment: None

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 39; injuries: none; flight instructor, commercial; airplane ratings: single-engine land; instrument ratings: helicopter; medical: class 2, without waivers/limitations; last flight review February 19, 2017; seat: left; restraint: 4-point; flight hours: 1,261 total, 95 in this make and model, 1,161 as pilot in command, 43 in the last 90 days, 9 in the last 30 days, 1 in the last 24 hours
- Student pilot; injuries: none; private; airplane ratings: single-engine land; medical: unknown; seat: right; restraint: 4-point; flight hours: 250 total, 10 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 210° at 6 knots, gusting 14
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 30 °F, dew point 19 °F
- Altimeter: 30.00 inHg
- Observed at: GYY, 5 nm away

## 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 20170911019259A](https://openairdocs.org/incident/20170911019259A), Sep 11, 2017: Hiller UH-12A, Griffith, IN, Substantial damage. While performing flight instruction in N2686, the PIC lost directional control of the aircraft. This loss of control resulted in damage to the helicopter tail…

## Other investigations on N2686 (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 NYC78FHM04](https://openairdocs.org/ntsb/NYC78FHM04), Sep 6, 1977: Hiller Acft UH-12C (N2686), Lincoln Park, NJ, destroyed

## Docket (5 files)

The files NTSB released with the investigation on April 11, 2019, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=96231. 4.3 MB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 3.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471851&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF
- Memorandum for the Record - FAA Inspector Phone Conversation (item 2, .PDF, 182 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471852&FileExtension=.PDF&FileName=Memorandum%20for%20the%20Record%20-%20FAA%20Inspector%20Phone%20Conversation-Master.PDF
- Schematic Diagrams of Tail Rotor Drive Components (item 3, .PDF, 252 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471853&FileExtension=.PDF&FileName=Schematic%20Diagrams%20of%20Tail%20Rotor%20Drive%20Components-Master.PDF
- Photo Array (item 4, .PDF, 2 photos, 197 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471854&FileExtension=.PDF&FileName=Photo%20Array-Master.PDF
- IHST Helicopter Accident/Incident Supplemental Checklist (item 5, .PDF, 56 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471855&FileExtension=.PDF&FileName=IHST%20Helicopter%20Accident%2FIncident%20Supplemental%20Checklist-Master.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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