Accident Boeing KC-135R Stratotanker 63-8877, Friday 3 May 2013
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Date:Friday 3 May 2013
Time:14:55
Type:Silhouette image of generic K35R model; specific model in this crash may look slightly different    
Boeing KC-135R Stratotanker
Owner/operator:United States Air Force - USAF
Registration: 63-8877
MSN: 18725/708
Year of manufacture:1964
Engine model:CFMI F108-CF-100
Fatalities:Fatalities: 3 / Occupants: 3
Other fatalities:0
Aircraft damage: Destroyed, written off
Category:Accident
Location:S of Chaldovar -   Kyrgyzstan
Phase: En route
Nature:Military
Departure airport:Bishkek-Manas International Airport (FRU/UCFM)
Destination airport:Bishkek-Manas International Airport (FRU/UCFM)
Confidence Rating: Accident investigation report completed and information captured
Narrative:
A US Air Force Boeing KC-135R Stratotanker aircraft left Bishkek-Manas Airport at 14:30 LT for a combat aerial refueling mission.
Upon takeoff, a flight control system malfunction, the board found, generated directional instability, causing the aircraft's nose to slowly drift from side-to-side or "rudder-hunt." This condition, not fully diagnosed by the crew, progressed into a more dangerous oscillatory instability known as a "Dutch roll." The board identified that a poor layout of key information in the inflight manual and insufficient crew training contributed to the mishap by detracting from the crew's ability to act on critical information during their troubleshooting to turn off either of two cockpit switches which may have eliminated the malfunction.
Having not recognized the Dutch roll condition, the crew initiated a left turn to remain on-course along the planned route of flight and used a small amount of left rudder to coordinate the turn. The use of rudder, while in a Dutch roll, increased the aircraft's oscillatory instability. The ensuing large side-to-side movements of the aircraft varied the crew member's foot pressure on the rudder pedal which caused inadvertent fluctuations in rudder position. These fluctuating rudder movements, coupled with slight right rudder use while rolling out of the turn, compounded the Dutch roll severity and produced extreme airframe stress that caused the KC-135's tail section to separate from the aircraft. The subsequent, uncontrollable descent resulted in an in-flight explosion.

Sources:

Air Mobility Command Public Affairs
Kloop.kg 3-5-2013
CNN 3-5-2013

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