CESSNA M337B near Avon Park, FL — 2010-11-18

Probable cause

The pilot's inadvertent encounter with an unexpected intense rain shower with severe turbulence at night.

NTSB narrative

Prior to the flight, the crew attended a mass briefing with the military training exercise personnel for whose operations the flight was to provide aerial support. The briefing included weather forecast information but did not include any indication of rain showers, thunderstorms, or other hazardous weather over the military operations area or near the landing airport for the period of operations. During the flight, the weather in the area began to deteriorate. Other pilots, ground personnel, and witnesses reported periods of heavy rain and reduced visibility. Infrared satellite imagery for the time period of the accident flight depicted an area of cumulus congestus cloud development over south-central Florida, north of a stationary frontal boundary, moving north. Ground personnel were monitoring the deteriorating weather as the accident airplane continued its mission. Although there may have been discussions of a weather recall, the evidence indicates that this did not occur. The accident pilot likely discontinued his mission and initiated a return to the airport due to the weather conditions. The airplane was not equipped with weather radar. As the airplane approached the airport from the north in night conditions, it encountered the edge of an area of echoes with a maximum core reflectivity of 55 decibels; such echoes are capable of producing severe turbulence and strong outflow winds. The right wing separated in flight, and the airplane crashed inverted in a farm pasture west of the airfield. An examination of the wreckage did not reveal evidence of a preexisting mechanical malfunction or failure. All observed fracture surfaces on the right wing showed indications of overstress.

NTSB coding

• Aircraft structural failure · Approach

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