Amateur-built RV-7A N92BF accident near Russell, Iowa

Probable cause

The noninstrument-rated pilot’s inadvertent entry into instrument meteorological conditions, which resulted in his spatial disorientation and the subsequent loss of airplane control.

NTSB analysis

The noninstrument-rated pilot was conducting a cross-country flight. GPS data indicated that the airplane departed and then proceeded west-southwest at an initial altitude of about 4,500 ft mean sea level (msl). About 20 minutes later, the airplane's track deviated from its initial heading, and the airplane began to climb. The airplane continued to climb at a slower groundspeed and reached a maximum recorded altitude of 7,769 ft msl; the groundspeed had slowed to 75 knots. The airplane then began a descending right turn, during which it reached a maximum groundspeed of 208 knots. During this time, the airplane was descending through 5,364 ft msl, and its descent rate reached more than 3,000 ft per minute (fpm). The last recorded point showed the airplane descending through 4,094 ft msl. During the last 52 seconds of the recorded data, the airplane lost 3,675 ft of altitude, and the descent rate had increased to more than 4,000 fpm. The airplane impacted a field, and examination of the wreckage revealed evidence consistent with a near vertical impact.

Postaccident examination of the airplane did not reveal any preimpact anomalies. A mechanic reported that the airplane's mechanical fuel pump had been replaced a few days before the accident; however, if the mechanical fuel pump had failed it would not have caused the steep descent during the final portion of the flight. Additionally, the electric fuel pump was operational and would have supplied the fuel necessary for engine operation.

The pilot was receiving flight-following services from air traffic control during the accident flight. In his last communication, the pilot reported to a controller that he had entered instrument meteorological conditions (IMC) and was trying to get "back on track"; he made this communication about the same time as the GPS data showed the airplane in the steep descending right turn. The controller advised the pilot to maintain visual flight rules, but the pilot did not respond. Weather conditions in the area at the time of the accident included overcast ceilings of 1,200 to 1,300 ft above ground level. No record was found indicating that the pilot received a preflight weather briefing; however, it could not be determined if the pilot obtained weather information using other sources. The restricted visibility conditions would have been conducive to the development of spatial disorientation, and the airplane's rapidly descending turn were consistent with the noninstrument-rated pilot inadvertently entering IMC and then losing airplane control due to spatial disorientation.

Toxicological testing of the pilot's specimens detected ethanol in the muscle and liver; however, it was likely produced postmortem.

Text from the NTSB. Open the NTSB docket for CEN14LA424 for the full record.