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Severe turbulence led to ExpressJet incident: TSB

On 5 September 2014, an Embraer 145LR departed Grand Rapids, Michigan, destined for Newark Liberty International Airport, New Jersey. After departure, the aircraft deviated north of its intended track into Canadian airspace to avoid a line of thunderstorms, and climbed to its cruising altitude with the intention of navigating its way through them. The aircraft flew through a large thunderstorm that it could not avoid and encountered severe turbulence. The flight crew lost control of the aircraft and it descended rapidly, losing approximately 4000 feet, before they were able to regain control. The aircraft continued to its destination, where it landed safely.

The TSB investigation found that the flight crew anticipated that they would be able to navigate between thunderstorms. However, as the flight progressed, the line of thunderstorms intensified, and the intended route became obstructed. As well, the report observed that, during the loss of control, the flight crew momentarily applied flight control inputs that exacerbated the roll attitude of the aircraft. As a result, recovery time and altitude loss were increased. The investigation further found that when flight crews operate an aircraft outside of manufacturer recommendations and its limitations, there is a risk of compromising flight safety, resulting in injury to the occupants or damage to the aircraft.

Following this occurrence, ExpressJet Airlines improved dispatcher use of flight-following software, and developed policy and procedures related to adverse weather phenomena. ExpressJet Airlines also developed a training module for all flight crew members to promote severe weather avoidance and weather radar utilization techniques to identify developing storm activity.