ERA12LA435 · Piper PA-42

The pilot reported that, before takeoff, he obtained a weather briefing that depicted an area of convective activity moving east of the departure airport. The airplane was equipped with an onboard satellite weather receiver, and, once airborne, the pilot contacted air traffic control and requested a deviation due to weather. The air traffic controller issued a deviation left of the planned course, and the pilot deviated accordingly. Shortly after reaching a cruise altitude of 23,000 feet mean sea level (msl) while in instrument meteorological conditions, the pilot saw a lightning flash, and the airplane subsequently entered a rapid ascent. Shortly after, he disconnected the autopilot and neutralized the flight controls, the stall warning sounded, and the pilot felt a "falling and twisting sensation." At this point, he suspected that the airplane was in a steep spiraling descent or spin; however, he could not confirm the airplane's attitude because the gyroscopic instruments had tumbled. Shortly after, the airplane exited the clouds, the pilot saw ground lighting, and he then initiated a recovery to a level flight attitude at an altitude of about 8,300 feet msl. After regaining control of the airplane, the pilot returned to the departure airport and subsequently landed without incident. The left and right elevators sustained substantial damage during the rapid descent.

A significant meteorological information advisory and a severe thunderstorm watch were valid for the accident area at the time of the accident and warned of the potential for severe thunderstorms, hail, extreme turbulence, and wind gusts. The preflight weather briefing obtained by the pilot included this information. Postaccident review of upper air soundings and weather radar images indicated that the airplane passed through an area with gravity waves that likely caused extreme updrafts and/or downdrafts, windshear, and turbulence. Although current weather forecasting technology is able to predict environments conducive to the generation of gravity waves and gravity-wave ducts, the technology lacks the ability to predict if, where, and at what intensity these phenomena may form. Therefore, neither the pilot's preflight weather briefing nor his onboard weather satellite receiver would have detected the gravity-wave conditions along the airplane's flight route.

Verbatim NTSB analysis and probable cause from the NTSB dataset