Amateur-built RV7 N977RV accident near Gibbon, Nebraska

Probable cause

The pilot’s improper decision to fly the airplane into known adverse weather and icing conditions which resulted in a loss of control.

NTSB analysis

Before taking off on an instrument-flight-rules (IFR) cross-country flight, the pilot obtained a standard weather briefing of the forecast and observed weather conditions along the flight route, which included thunderstorms, convective Significant Meteorological Information (SIGMETs), and Airmen’s Meteorological Information (AIRMETs) for icing conditions.

A review of air traffic control (ATC) information revealed that, while the pilot was en route to the destination airport, an air traffic controller told the pilot that there was moderate to heavy precipitation about 5 miles ahead and the pilot acknowledged. About 4 minutes later, the pilot requested a lower altitude due to ice accumulation. ATC gave the pilot a block altitude to maintain and the pilot began to descend the airplane. About 40 seconds later, ATC told the pilot he could descend below the block altitude if needed. The pilot acknowledged by saying, “roger.” Immediately after the pilot acknowledged that he could go lower, ATC told him that if he was turning toward the west, there was extreme precipitation that extended to the southwest. The pilot did not respond. ATC made several subsequent attempts to contact the pilot; however, the pilot never responded.

The airplane impacted a grass field and was destroyed. Airplane debris was scattered in the field for several hundred feet. The rudder and vertical stabilizer separated from each other and most of the pieces of the rudder and vertical stabilizer were found before the impact site in a tree and on the ground.

The investigation estimated the airplane’s airspeed based on recorded ADS-B data and atmospheric conditions at the time of the accident. The ADS-B pressure altitude data was used to calculate the vertical airspeed at the end of the flight based on the rate of descent. The computed maximum airspeed at the last reliable pressure altitude, about 10 seconds before impact, was about 286 KTAS, which surpassed the never exceed speed (Vne) listed in the airplane’s pilot operating handbook of 210 knots.

Analysis of the ADS-B data also revealed that, in the final 2 minutes of flight, the airplane pitched back and forth between 10° above the horizon and -60° below the horizon and rolled to the right at bank angles between 10° and 120°.

Examination of the separated rudder and vertical stabilizer depicted signatures of overstress, and the location where they were found indicated that they separated from the airplane before impact. However, due to their proximity to the rest of wreckage, the separation likely occurred immediately before impact and the inflight breakup was not causal to the accident. The vertical stabilizer and rudder separated from the empennage due to “rudder flutter” when the airplane exceeded the Vne for the airplane. Examination of the engine and remaining systems revealed no mechanical anomalies.

Based on the pilot’s reported accumulation of ice, the adverse weather conditions, and the airplane’s variations in pitch and roll in the final minutes of flight, the pilot likely experienced a loss of control after encountering adverse weather due to a combination of ice accumulation on the airplane’s control surfaces.

Toxicological testing revealed ethanol was present in samples taken during the autopsy. Given the putrefaction of the samples, it is likely that all detected ethanol was the result of postmortem production.

Text from the NTSB. Open the NTSB docket for CEN23FA220 for the full record.