ERJF15

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.

JerkStore

I knew Captain Voss. He was a good dude. May the whole crew rest in peace.

Fly Boeing Jets

Sadly, three lives were lost because the AF stopped teaching large aircraft aerodynamics many years ago. When I went through the program, we were all given a manual by Boeing that talked in depth about dutch roll and high speed buffet. Though, none of the instructors ever took a moment to review those items with us. Thankfully, my airline actually spent a couple days on those subjects.

TankerDriver

Yes, ironically as TACC continues to file us in the low to mid 40's to save a buck, we've got young, inexperienced aircrews flying in coffin corner. Good thing our autopilots are problem free.

Purple Drank

How many 135 pilots could troubleshoot, diagnose, and properly fix that problem at any experience level?

What a terrible waste of such good people.

iceman49

Its all about training and proper documentation, something that has been sacrificed to the bottom line in much of aviation. What a waste.

badflaps

What was it? Yaw damper problem?

block30

Thanks for posting this ERJF15. Certainly this is sad, and I feel for the families left behind.

I just found this. Wasnt sure if this was a thread derailment or not, mods do with as you please. Thoughts on the article???
How to Halt Dutch Roll |

Dutch roll—the combined yawing and rolling motion that all airplanes exhibit to some extent—is almost a thing of the past due to better aerodynamic designs, and more importantly, the almost universal use of yaw dampers. But Dutch roll can be serious, especially in swept wing airplanes flying in the thin air of high altitude.

We all remember from ground school that Dutch roll is caused by yawing motion which adds a little airspeed and thus a little more lift to the advancing wing. That bit of extra lift causes the airplane to roll as well as yaw. In an airplane with neutral Dutch roll damping the yawing and rolling will continue until some control input stops the motion. Some airplanes, particularly early swept wing jet designs, had very little natural Dutch roll damping, or even divergent Dutch roll so each yaw-roll combination would grow in amplitude. In at least a few instances Dutch roll demonstrations got out of hand and the severe stress of the yawing and rolling tossed an engine off the wing.

In more recently designed jets the Dutch roll damping is at least a little positive and most are controllable without the yaw damper functioning. However, passengers would rebel against any intentional flight without the yaw damper operating because nothing stirs the stomach quite as quickly as Dutch roll.

There is, however, an old trick to end Dutch roll, particularly in a jet, that I had never learned until recently. But it’s something military pilots who flew the early jets learned in training.

In test pilot speak Dutch roll is a second order phenomenon. They describe it mathematically, but bottom line is that the roll and yaw are linked. One causes the other. So, to halt Dutch roll you need to disrupt one motion, either yaw or roll.

Using the rudder to stop Dutch roll is obvious, and that’s what the automatic yaw dampers do. With their electronic sensors and brains the yaw damper can move the rudder almost instantly to counteract yaw.

However, we humans need time to recognize the yawing motion, calculate how much pressure to put on which rudder pedal, and then for our muscles to react. That’s usually too much time for us to make the proper rudder input to halt the yaw.

But the Gulfstream test pilots showed me, as part of a new advanced pilot training program they are developing, an old trick with the ailerons that halts Dutch roll almost immediately. What you do is move the wheel back and forth a few degrees as quick as you can. This small and rapid movement of the ailerons disrupts the rolling motion and uncouples it from yaw.

When I was told to “just move the wheel back and forth” I did, and it didn’t work. I was making the movements too slowly. You need to wiggle the wheel like a madman and then the Dutch roll stops like magic.

Who knew wheel wagging would stop Dutch roll. Turns out pilots who went through military jet training decades ago do.

Twin Wasp

Braniff lost a 707 on a training flight in 1959 doing Dutch rolls. It got so bad they lost 1, 2 and 4 - as in departed the airframe. We don't seem to have learned anything in 50+ years.

We used to play "whack-a-mole" in the 727. I taught guys not to try to beat down both wings, you'd just get out of sync and make it worse. Wait for your wing to start up and then roll and release, as fast as you just read that.

tomgoodman

That works, but we found that an easier solution was to extend just a few degrees of spoilers. The Dutch roll stops almost immediately.