Robinson Helicopter Company R44 N494SH accident near Port O'Connor, Texas

Probable cause

The pilot’s initiation of the visual flight into instrument meteorological conditions, which resulted in spatial disorientation and a subsequent loss of helicopter control. Contributing to the accident was the pilot’s flicker vertigo during the flight.

NTSB analysis

The helicopter impacted terrain shortly after the non-instrument-rated pilot took off from his residence for the night flight. A neighbor observed the helicopter’s red anti-collision (strobe) light operating as it departed. The neighbor reported that it was extremely foggy and she could “barely see” her boat dock, which was about 75 ft away. There were no known witnesses to the accident. The helicopter impacted the terrain and a postimpact fire ensued.

Recorded data from on board the helicopter showed that it departed from a road next to the pilot’s residence and traveled toward a swamp area that contained little to no ground reference lighting. ADS-B data for the accident flight showed a fight path starting from an area near the pilot’s residence. The helicopter traveled to the east, passed over a lake, and then performed a turn to the north. The helicopter climbed and then descended toward the south. The ADS-B data terminated over an open field next to a home. The direct distance from where the helicopter departed from to the accident site was about 0.25 miles.

While a postimpact fire consumed most of the wreckage, an examination revealed no preimpact mechanical malfunctions or failures with the airframe or the engine. The helicopter was found to be equipped for instrument flight; however, the helicopter was not certified for instrument flight rules.

A search revealed that the pilot did not receive an official weather briefing before initiating the flight.

The pilot’s toxicological testing detected ethanol at a very low level in cavity blood. Ethanol was not detected in vitreous fluid or urine. These results indicate that some or all of the detected ethanol may have been from postmortem production. It is unlikely that ethanol contributed to the accident. The toxicological evidence also indicates that the pilot had used cetirizine. Whether the pilot was experiencing some sedating effects of this medication at the time of the accident is uncertain. Based upon the pilot’s initiation of flight at night in instrument meteorological conditions (IMC), it is unlikely that the pilot’s use of cetirizine contributed to the accident. The autopsy’s cardiac findings are non-specific and unlikely of significance to the accident.

The pilot had the anti-collision (strobe) light activated during the flight. Usage of an anti-collision (strobe) light during flight through clouds can cause flicker vertigo and subsequent spatial disorientation. In addition to spatial disorientation, the pilot likely also experienced flicker vertigo before the impact with terrain.

It is likely the non-instrument-rated pilot’s decision to initiate flight in night IMC resulted in spatial disorientation, a loss of control during the initial climb, and a subsequent impact with terrain.

Text from the NTSB. Open the NTSB docket for CEN23FA125 for the full record.