Updated: Jun 6
First, I usually take some time to look at most general aviation accidents that might involve weather. Often there are lessons learned even before the final NTSB report. Nevertheless, the NTSB will be looking into the tragic accident of a Lancair Evolution that plummeted out of the sky from 25,000 feet over southern Ohio on the morning of May 28, 2021.
Second, I usually refrain from making any conclusions about what might have caused the accident. Instead I try to paint the environment that was present at the time of the accident. According to the Flightaware track, the pilot departed KEDJ (Bellefontaine Regional Airport) in west-central Ohio at 1415Z headed southeast to KCHS (Charleston, South Carolina). The pilot climbed and leveled off at 25,000 feet 25 minutes later at 1440Z. Then approximately seven minutes later at 1447Z, the pilot departed controlled flight.
I have read numerous accounts on some aviation forums that "he must have flew into a thunderstorm" or that was somehow related to a "downdraft" or "wind shear." Or, someone posted an icing chart that is valid 5 hours after the accident which has zero relevance. Ugh! While weather may have contributed to the accident, it wasn't due to the pilot flying into a thunderstorm or encountering convective wind shear aloft. Yes, it was a convectively charged atmosphere in the area, but the flight terminated 20 miles prior to any area of precipitation as can be seen below. The red circle is the approximate location of the accident.
In fact, there were no convective SIGMETs along that route at 1455Z (see below). There was a convective outlook area for the route, but that indicates in the next two to six hours forecasters expect to see convection develop in that area that meets convective SIGMET criteria. Therefore, outside of the convective SIGMET shown in northern West Virginia, forecasters did not believe other precipitation areas met the convective SIGMET criteria.
Even if you look an hour earlier at 1355Z, a similar convective outlook was present, but there were no convective SIGMETs along a direct route.
Moreover, if you look at the visible satellite image below that is valid at the time of the accident, the region around the accident site looks like there are mostly clear skies with a significant break in the clouds. The closest airport with an observation is KPMH which was essentially reporting no major cloud cover below 12,000 feet AGL.
KPMH 281459Z AUTO 22003KT 10SM SCT110 24/18 A2981 RMK AO2=
KPMH 281359Z AUTO 20004KT 10SM CLR 23/18 A2983 RMK AO2=
Perhaps the biggest threat is the possibility of moderate to heavy icing conditions on the climb out of KEDJ. However, it is unlikely this aircraft had a certified ice protection system (IPS). The climb to 25,000 feet likely exposed the aircraft to significant icing conditions from the freezing level at 12,000 feet up to 25,000 feet. Below is the Current Icing Product (CIP) valid at 1400Z and at 17,000 feet showing moderate to heavy ice through west-central and south-central Ohio. This looked very similar at other altitudes between 15,000 and 19,000 feet.
The nearest radiosonde launch site is in Wilmington, Ohio about 50 miles to the northwest of the accident site. The weather balloon is launched at 1100Z, so given the distance and time it is not as relevant, but is often one of the data components the NTSB will include in their meteorology report. It does, however, capture the freezing level of ~11,457 feet MSL which is likely a good estimate for that general area. The temperature at 25,000 feet is approximately -22°C.
Worth noting below is the moist instability (temperature and dewpoint follow parallel to the moist adiabatic lapse rate) that exists between 15,000 and 22,000 feet. Although the dewpoint depression is about 2°C in this altitude range, it's likely there was some liquid water in that layer. One obvious hint is that the temperature takes a hard left turn at the top (~22,000 feet) which is a sign of what is called "wet bulbing" where the temperature sensor on the radiosonde pops into clear air and starts to evaporate liquid on the sensor or more likely sublimate ice off the sensor.
Below is the Rapid Refresh sounding analysis valid at 1500Z in the location where the pilot was climbing through about 19,000 feet. Given the moist instability showing up on this analysis and the CIP analysis depicting moderate and heavy icing, it is very likely the aircraft was accreting ice in the climb.
During the climb, this kept the aircraft in the prime temperature regime for airframe icing. While airframe ice is less likely once the static air temperature becomes colder than about -12°C, it doesn't drop off to zero. In fact, there's a reasonable expectation in a convective environment for airframe icing to exist down to -30°C. In the graph shown below from a study done at NCAR, there are still plenty of reports of airframe icing below -20°C. In fact, the Current Icing Product (CIP) and Forecast Icing Product (FIP) typically cut off the likely of icing at -25°C and colder unless there's convective activity and then the threshold goes down to -30°C.
While this doesn't imply that icing was a factor in this accident, it certainly was a threat during the climb and may have contributed to a higher stall speed upon reaching the top of climb assuming there were ice accretions on the airframe. However, I can say with some certainty, it is not likely due to the pilot flying into a thunderstorm.
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Most pilots are weatherwise, but some are otherwise™
Dr. Scott Dennstaedt
Weather Systems Engineer
CFI & former NWS meteorologist