CEN24FA326 · Rans S19

The airplane departed in daylight, visual weather conditions and proceeded along a meandering flight path before heading towards Yankton, South Dakota, for an unknown destination. About an hour after departure, while over Yankton, the pilot made a telephone call to a friend to inquire about the weather and airport options, stating that he was unable to land due to the weather as he did not hold an instrument rating. The pilot was not instrument rated, the airplane was equipped for only visual flight rules (VFR) operations, and the weather conditions at the nearby airport included a cloud ceiling at 200 ft above ground level (agl) with 1/4-mile visibility in fog and light rain. The friend suggested two airports south of the pilot’s position with automated weather stations reporting VFR weather conditions. The friend also stated that the pilot seemed calm and did not mention if he was in instrument meteorological conditions (IMC). A NTSB weather study determined that a cold front and inversion in the area, along with low- and mid-level troughs, made for an environment conducive to sustained low-level cloud cover, moisture, and precipitation. A review of recovered flight track data from an onboard GPS unit revealed that about the time that the pilot called his friend, the airplane was at an altitude of 3,239 ft mean sea level (msl) tracking roughly southwest. The flight track remained consistent during the next 8 minutes for about 14 nm, suggesting that the pilot was in VFR conditions above the cloud tops. The airplane then began a right turn to the west with a slow climb to a maximum altitude of about 4,000 ft msl. About 1 minute later, the airplane began an S-turn, followed by a descending left turn for less than a minute before the data was lost. The accident site was located about 3/4 nm northeast of the last data point. The weather study determined that the accident flight was likely in IMC from 3,500 ft msl down to 200 ft agl, with visibility restricted to 1/4 mile or less below the cloud cover. The study also noted that a band of rain showers was moving northeast across the accident site at the accident time, which likely further reduced visibility below the cloud layer and had associated convective turbulence. A postaccident examination of the airplane revealed no evidence of mechanical malfunction or failure that would have precluded normal operation. However, flight control continuity could not be established due to impact damage. It is unknown what, if any, weather information the pilot checked before or during the flight, or whether the nearby airport (at the time that the pilot called his friend) was the intended destination. However, the reported weather at that airport from more than 2 hours before the accident flight departed through the time of the accident consistently included low instrument flight rules (LIFR) conditions. (LIFR is defined as a ceiling below 500 ft agl and/or visibility less than 1 mile.) The weather forecast information applicable for the accident time did not include any graphical or text AIRMETs for instrument flight rules (IFR) conditions, and no terminal aerodrome forecasts were available within 30 miles of the accident site. The National Weather Service (NWS) graphical forecast analysis products issued more than 3 hours before the accident flight departed forecast LIFR surface visibility for the area of the accident applicable about 1 hour 40 minutes before the accident and VFR surface visibility with a cloud ceiling at 2,300 ft msl (about 600 ft agl) for the area of the accident applicable about 1 hour 20 minutes after the accident. The weather conditions encountered by the accident pilot were worse than NWS forecasts valid for the accident time. Several pilot reports (PIREPs) reported cloud tops between 2,600 ft MSL and 3,500 ft MSL in the area. Loss of external visual references during VFR flight presents a high risk of spatial disorientation and loss of control. Several risk factors for spatial disorientation were present in this accident: the lack of IFR flight instruments, the non-instrument rated pilot, and the weather conditions. Based on these factors, as well as the airplane’s flight track and the orientation and fragmentation of the wreckage consistent with a high-energy impact, the pilot likely experienced spatial disorientation after entering an area of rain, convective turbulence, and IMC which may have been higher than the surrounding cloud tops, and he subsequently lost control of the airplane.

Verbatim NTSB analysis and probable cause from the NTSB dataset