Air Mobility Command Public Affairs
3/13/2014 - SCOTT AIR FORCE BASE, Ill. -- Air
Mobility Command has released the results of an accident investigation
that examined what caused the May 3, 2013, crash of a KC-135 in the
Kyrgyz Republic. The crew of three, en route from the Transit Center at
Manas to Afghanistan on a combat aerial refueling mission, perished in
the mishap.
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.
"Our hearts go out to the family members and friends of these Airmen,"
said Brig. Gen. Steve Arquiette, who led the accident investigation
board. "Having attended the memorial service at Manas and later
interviewing many co-workers, I know these Airmen were highly regarded
and are greatly missed. The investigation team, with the help of our
industry and Kyrgyz government partners, pushed through months of
intense fact finding for the primary purposes of understanding what
happened that day and to honor the crew's service to our nation."
The three Airmen who perished are:
Tech. Sgt. Herman Mackey III, 30, of Bakersfield, Calif.
Capt. Victoria Ann Pinckney, 27, of Colorado Springs, Colo.
Capt. Mark Tyler Voss, 27, of Boerne, Texas
A unique combination of six factors--flight control malfunctions,
insufficient crew force training, incomplete crew checklist response,
use of rudder while in a Dutch roll condition, crew composition, and
cumbersome procedural guidance--all came together during the flight's
short 11-minute duration and resulted in this accident.
"The crew encountered a condition that they had not realistically
experienced in training, and when coupled with decisions based on their
relatively low recent experience levels, were presented with an
unrecognized hazardous and difficult situation to overcome," the general
said. "It has been the focus of our investigative team, throughout
these months of hard work and travel to the accident scene in the Kyrgyz
Republic, to do everything we can to fully understand the facts
surrounding this tragic string of events."
The aircraft was assigned to the 22nd Air Refueling Wing at McConnell
Air Force Base, Kan., and was flown by members of the 92nd Air Refueling
Wing at Fairchild Air Force Base, Wash. The crew and aircraft were
flying out of the 376th Air Expeditionary Wing at the Transit Center
Manas.
The report is available on the Air Force Freedom of Information Act Reading Room website, https://www.efoia.af.mil/palMain.aspx.
Thursday, March 13, 2014
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