SCHWEIZER AIRCRAFT CORP G-164D near Butte City, CA — 2013-05-16

Probable cause

The pilot's failure to maintain airplane control after an encounter with wake turbulence while maneuvering at low altitude. Contributing to the accident was the pilot’s fatigue due to extended hours of wakefulness and high workload.

NTSB narrative

The pilot reported that he was at a low altitude and in a turn for the next agricultural aerial application run when the airplane encountered its wake turbulence, and the inside wing stalled. He tried to apply rudder to recover, but the airplane inverted and pitched nosedown before it impacted terrain. The pilot reported no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation. The pilot awoke at 0445 on the day of the accident. He had been awake for over 15 hours and had flown 71 application loads during 12 of those hours at the time of the accident. Due to the early wake time and high work load, the pilot was most likely fatigued at the time of the accident.

Analysis

Primary failure mode

Loss of control

First missed decision gate

Avoiding wake turbulence during the turn could have prevented the stall.

NTSB coding

• Inflight upset · Maneuvering-low-alt flying

Evidence available

• 1 docket document

Docket documents1

• Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1form

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