Three USAF personnel died when the KC-135R, call sign “Shell 77,” crashed just 11 min. after takeoff from Manas International Airport, on May 3, 2013. The aircraft was one of several KC-135s forward-based in the former Soviet republic flying aerial refueling operations for combat aircraft supporting ground troops in Afghanistan.
Accident investigators concluded in their March 6 report that while the primary causal factors were a factor, those problems had been exacerbated by crew inexperience and by subpar organizational training programs, crew composition, and cumbersome procedural guidance.
The problems began shortly after the afternoon takeoff from Manas. As the aircraft got airborne the crew immediately began to experience a flight condition known as rudder hunting, which prompted the aircraft's nose to yaw left and right by 1 deg., an issue caused by a malfunction with the aircraft's series yaw damper (SYD)—part of the KC-135R's flight-control augmentation system (FCAS). The crew identified the SYD as a potential source of the issue but instead of turning the system off, they attempted to correct the yawing motion by using rudder and aileron inputs as well as turning on the autopilot, causing the oscillations to worsen. Some yawing issues had been reported during the aircraft's transit flight to Manas from RAF Mildenhall, U.K.
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