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ASN Wikibase Occurrence # 165063
Last updated: 26 August 2021
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Type:Silhouette image of generic B06 model; specific model in this crash may look slightly different
Bell OH-58A Kiowa
Owner/operator:Kern County Sheriffs Department
Registration: N497E
MSN: 69-16375
Fatalities:Fatalities: 0 / Occupants: 3
Aircraft damage: Substantial
Location:East of Tehachapi, CA -   United States of America
Phase: En route
Departure airport:Bakersfield, CA (BFL)
Destination airport:Lancaster, CA (WJF)
Investigating agency: NTSB
The intent of the public aircraft flight was to transport an injured dog from the Sheriff Departmentís K-9 division to an urgent care facility after it had been shot while on duty. After arriving at the Sheriffís Air Support Unit (ASU) headquarters about 0100, the pilot discussed the weather conditions with the on-duty command pilot and confirmed that visual meteorological conditions prevailed at both the departure and arrival airports. He was aware that a weather front was moving through the area and that he would likely encounter instrument meteorological conditions while en route. Therefore, he planned to use an airport about halfway along the route as a backup landing site if the weather conditions deteriorated. The pilotís decision to attempt the flight with known deteriorating weather conditions was likely due to self-induced pressure to complete the flight because of the dogís injury.†
The departure was uneventful, but, as the helicopter approached the alternate airport, it encountered light rain, strong wind, low clouds, and fog. The pilot decided to proceed and see if the helicopter could traverse a pass east of the airport. However, once the flight got beyond the lights of the city, the pilot lost all visual reference after flying into clouds; the helicopter was about 500 ft above ground level at this time. He decided to slow the helicopter and initiate a gradual descent to exit the clouds. Unknown to the pilot, the windshield had misted up due to a water leak, which limited the effectiveness of the night vision goggles (NVG) that he and the tactical flight officer (TFO) were using for the flight. During the descent, the TFO realized that the windshield had fogged up because he could still see out of the side window, and the pilot turned on the de-mister. Shortly after, a highway came into view, and the helicopter struck its surface about 5 miles past the alternate airport. The helicopter bounced and then rotated about 180 degrees. It appeared to be handling normally, so the pilot chose to return to the alternate airport. Upon landing, he discovered that the helicopter had sustained substantial damage.
The weather conditions at the alternate airport were below the ASU minimums both before takeoff and during the flight. However, the ASU did not have formal risk assessment procedures in effect. The weather conditions at night and the misted windshield would have been conducive to the pilotís experiencing spatial disorientation.
Although the helicopter was equipped with a radar altimeter, its audible and visual alert functions were turned off at the time of the accident. If the pilot had used the radar altimeter, it would have given him an opportunity to react when the helicopter reached or descended below a predetermined altitude. The pilot, who was also the ASUís chief flight instructor, admitted that the typical effectiveness of the NVGs likely led to complacency on his part.
The pilot had been working the day leading up to the accident and had been awake for about 16 hours. He reported that he was about 2 hours into restful sleep when he was woken to perform the mission. Therefore, he attained minimal rest for the mission, which was performed during a time when he would otherwise be asleep and likely degraded his performance and decision-making ability.

Probable Cause: The pilot's decision to attempt a mission at night with known en route weather conditions below operating minimums, likely due to self-induced pressure, and then continue flight beyond the alternate landing airport as weather conditions deteriorated, which resulted in the pilot experiencing spatial disorientation. Contributing to the accident were the pilot's fatigue, his failure to recognize that mist had formed on the inner surface of the windshield, his complacency due to the effectiveness of the night vision goggles, and his failure to use the radar altimeter.



Accident investigation:
Investigating agency: NTSB
Status: Investigation completed
Download report: Final report

Revision history:

29-Mar-2014 06:51 Geno Added
11-Apr-2014 20:37 Geno Updated [Location, Departure airport, Destination airport, Source, Damage, Narrative]
13-Mar-2016 20:54 Aerossurance Updated [Phase, Source, Narrative]
28-Mar-2016 20:34 Aerossurance Updated [Operator, Source, Narrative]
21-Dec-2016 19:28 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
29-Nov-2017 13:40 ASN Update Bot Updated [Cn, Operator, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative]

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