BEECH S35 near Knoxville, TN — 2015-10-07

Probable cause

The pilot's inadequate preflight weather planning and his improper decision to attempt a visual flight rules flight in night instrument metrological conditions, which resulted in spatial disorientation and subsequent collision with terrain.

NTSB narrative

The airplane had been topped off with fuel the day before the accident flight. Early the following day, the pilot arrived at the airport for the visual flight rules flight and completed a preflight inspection, then he and his passenger boarded the airplane. According to the pilot, while taxiing to the runup area for the runway, he listened to the automated weather observation system (AWOS) at the airport and thought he heard that the ceiling was about 200 ft, even though he could "look up at the sky and see stars." He also stated that this was also not compatible with his weather briefings from the night before or earlier the morning of the accident. According to the passenger, the morning of the accident was dark and foggy, and he could not see the sky. He remembered asking the pilot about instrument procedures as he believed the pilot was instrument qualified. The pilot and passenger could only remember the preflight, the engine warmup, the takeoff, and the landing gear retraction. After departure, the airplane impacted trees and vegetation about 10 ft above ground level about 600 ft from the departure end of the runway. The airplane then impacted in an open field in a level attitude with the wing flaps retracted and the landing gear in the up position. Both the pilot and passenger were seriously injured during the impact sequence. The airport's line service manager arrived at the airport about 20 minutes after the accident occurred and stated that he could not see anything and that it was "zero/zero." The traffic patrol pilot for the local radio station tried to take off to try to locate the airplane, but the visibility was too bad. There was no record of the pilot receiving a formal weather briefing. Review of the weather conditions before the accident revealed that the National Weather Service had been forecasting fog and low clouds for at least 5 hours before the time of the accident, the AWOS had been reporting 1/4 mile visibility for at least 15 minutes before the accident, and the sun had not yet risen. If the pilot had delayed his departure until midmorning, he would have been able to depart in visual meteorological conditions. Postaccident examination of the airframe, engine, and recorded engine data did not reveal any preimpact failures or malfunctions that would have precluded normal operation. Examination of the accident site and airplane revealed that the impact with the ground was at high speed with the engine at takeoff power, indicative of the pilot not climbing the airplane after takeoff. It is likely that, during the takeoff from the well-lit runway into a dark sky with no ambient light, the pilot experienced a somatogravic illusion in which he likely sensed that the sudden linear acceleration of the airplane created a pitch-up sensation, when instead the airplane was not climbing or climbing shallowly. It is likely that, with no other visual cues, the pilot became spatially disoriented and pushed the nose down to avoid what he sensed was pitching up too high and impacted the trees at the end of the runway.

Analysis

Primary failure mode

Spatial disorientation

First missed decision gate

Pilot should have delayed takeoff due to low visibility and fog conditions.

NTSB coding

• VFR encounter with IMC · Initial climb
• Decision Making / Judgment
• Planning / Preparation
• Spatial Disorientation

Evidence available

• Photos
• 13 docket documents

Docket documents13

• PILOT/OPERATOR AIRCRAFT ACCIDENT REPORT, NTSB FORM 6120.1form
• STATEMENT OF PARTY REPRESENTATIVES TO NTSB INVESTIGATIONform
• WITNESS STATEMENTS AND INTERVIEW SUMMARIESinterview
• FUEL RECORDSother
• PHOTO ARRAYphotos
• SATELLITE IMAGE OF ACCIDENT AREAphotos
• ATTACHMENT 1 TO ELECTRONIC DEVICES - SPECIALIST'S FACTUAL REPORTreport
• ELECTRONIC DEVICES - SPECIALIST'S FACTUAL REPORTreport
• WEATHER REPORTS AND RECORDS - KDKX AWOS DATAreport
• WEATHER REPORTS AND RECORDS - KTYS METARS AND TAFSreport
• WEATHER REPORTS AND RECORDS - NTSB WEATHER STUDYreport
• WEATHER REPORTS AND RECORDS - USNO ASTRONOMICAL DATAreport
• WRECKAGE RELEASE AND EVIDENCE CONTROLwreckage

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