# NTSB CHI94LA287: Hughes 369HS, N74AW, Custer, SD, August 18, 1994

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: August 18, 1994, 14:45 local (20:45 UTC)
- Place: Custer, SD
- Coordinates: 43.760066, -103.600425 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=43.7601&lon=-103.6004&mi=10
- Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report January 25, 1995
- Report: Approved by Office Director
- NTSB case key (mKey): 9644
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI94LA287
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/9644/pdf
- Page: https://openairdocs.org/ntsb/CHI94LA287

## Probable cause

the pilot's selection of unsuitable terrain on which to perform an autorotation.  A factor in this accident was the hidden obstruction.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Hard landing, landing - flare/touchdown
  - terrain condition - hidden obstruction(s) (contributing factor)
  - unsuitable terrain or takeoff/landing/taxi area - selected, pilot in command (cause)
  - autorotation - performed, pilot in command
  - emergency procedure - simulated

## Analysis

THE PILOT WAS PRACTICING AUTOROTATIONS IN HIS HELICOPTER.  DURING HIS SECOND AUTOROTATION THE HELICOPTER'S SKID COLLIDED WITH A ROCK CAUSING THE HELICOPTER TO ENTER GROUND RESONANCE.  THE PILOT SAID THE HELICOPTER'S ROTOR BLADES BEGAN '...GYRATING OUT OF THE NORMAL PATH...' STRIKING THE AIRFRAME NUMEROUS TIMES.  THE PILOT SAID THE ROCK HIS AIRCRAFT COLLIDED WITH WAS OBSCURED BY GRASS AND THAT HE DID NOT SEE IT.  HE SAID HE DID SEE OTHER ROCKS OUT IN FRONT OF HIS AIRCRAFT AS IT DESCENDED.

## Factual narrative

On August 18, 1994, at 1445 mountain daylight time (mdt), a Hughes 369HS, N74AM, registered to X Data Corporation of Rapid City, South Dakota, and piloted by a commercially certificated pilot, was substantially damaged during landing following an auto-rotation demonstration.  Visual meteorological conditions prevailed at the time of the accident.  The 14 CFR Part 91 flight was not operating on a flight plan.  The pilot and passenger reported no injuries.  The flight departed Custer, South Dakota, at 1443 mdt.

The pilot's written statement on NTSB Form 6120.1/2 said, "...practicing touch down auto rotation landing procedure.  Upon touch down, right landing skid connected with rock not visible due to ground cover in area.  At time of impact with rock, helicopter was jolted over approximately 4 to 6 inches sideways causing ground resonance."  The pilot stated the rotor blades began "...gyrating out of normal path..." and struck components on the helicopter.  According to the pilot, the terrain used for the landing had been used in the past without any incidents.  He said the terrain was a "... rolling, grassy field with no visible obstructions."

An interview with the pilot revealed that he did one autorotation before the one that resulted in the accident. The pilot said he observed rocks in front of the helicopter, but not below during the autorotation.  According to the pilot, the rock his helicopter struck was obscured by tall grass.

## Aircraft

- Registration: N74AW (not matched to a registry record)
- Reported make and model: HUGHES 369HS
- Category: Helicopter
- Serial number: 1250790S
- Airframe hours: 13589
- Engines: ALLISON 250-C20 400 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: Wild West Helo Tours, Inc
- Registered owner: X Data Corporation
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, August 10, 1994, 14 hours before

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 41; commercial; airplane ratings: single-engine land; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 3,779 total, 424 in this make and model, 3,729 as pilot in command, 110 in the last 90 days, 53 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Visibility: 40 statute miles
- Lowest ceiling: 24,000 ft broken
- Temperature: 90 °F, dew point 52 °F
- Altimeter: 29.00 inHg
- Observed at: RAP, 20 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 19940818021789A](https://openairdocs.org/incident/19940818021789A), Aug 18, 1994: Hughes 369HS, Custer, SD, Substantial damage. On second demo autorotation landing a skid hit rock hidden by tall grass. Caused ground resonance and roll over.

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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