Air Force Grounds Kc-135S Problems Resurface With Gears In Horizontal Stabilizer Mechanism

For the second time in six months, the Air Force has grounded a significant portion of the nation’s KC-135 aerial refueling tankers.

The service grounded the KC-135 tanker jets Friday after finding problems with two small gears in an assembly it started replacing last fall, according to Maj. Harry Edwards, an Air Force spokesman at Wright-Patterson Air Force Base near Dayton, Ohio.

The order affected 198 - or 36 percent - of the 546-jet fleet. However, 75 of those affected already were on the ground for routine maintenance or modification.

The stand-down affects 11 of the 54 tankers assigned to Fairchild Air Force Base just west of Spokane. Fairchild is one of the world’s largest tanker bases.

The gears - about the size of half a coffee cup - are associated with the jet’s horizontal stabilizer trim actuator, a mechanism the Air Force thought it had fixed. Inspections last August and September had raised concerns about the assembly.

“We want to emphasize that there were no accidents, no incidents or system failures associated with this most recent stand-down,” Edwards said. “This is precautionary.”

The gear problems are not related to the crash of a Fairchild-based tanker jet in Germany in January 1999, he said.

“It was part of a review process. They were reviewing the part manufacture and they found the process was incorrect,” Edwards said.

The actuator is a brake and jackscrew system that moves the small wings - called horizontal stabilizers - at the rear of the plane. Those stabilizers move a jet’s nose up or down in flight.

Failure of the gear could result in a jammed stabilizer that wouldn’t respond to a pilot’s commands.

“No, you wouldn’t be able to recover,” said Senior Master Sgt. Don Schmidt, a spokesman at Scott Air Force Base in Illinois. “If you’re going up, you’d keep going up. If you’re going down, well … ”

The stand-down will cause the Air Force to reshuffle some missions and postpone or cancel others.

“But we could go to war tomorrow if we had to,” said Lt. Col. Charles Wynne, another spokesman at Scott.

The U.S. only used about 150 tankers for its operations at the height of the Kosovo air war, Wynne said.

“I can’t comprehend a conflict where we would have to take these out of the stand-down because we have so many other tankers we can use,” Wynne said.

Of the Air Force’s 546 tankers, there are 270 ready to fly missions. However, almost all of those have some sort of restriction on how they operate, which could include prohibitions on certain kinds of landings or not being allowed to refuel some large aircraft in flight.

Some of the jets have restrictions related to the actuators, but Wynne did not know how many.

The rest of the fleet is either grounded because of the gears, undergoing modifications or down for routine maintenance. There are 19 jets deployed overseas.

Missions that might be postponed or canceled include training, moving cargo and shuttling aircraft across the planet with aerial refueling.

The gears were manufactured at the Ogden Air Logistics Center at Hill Air Force Base, Utah.

Last August and September, the Air Force ordered inspections of the primary and auxiliary brake systems of the actuator. By late September, 139 aircraft were grounded after failing the inspections.

The Air Force began removing the assemblies and having them remanufactured, but some of those remanufactured assemblies did not meet specifications and had to be removed again.

Now the gears in the actuator assembly have raised a new problem. This time the grounded portion of the fleet may not be ready to go until July, Edwards said.

He emphasized that was a very rough estimate, as was the cost of fixing the gears - $1,000 per plane.

The horizontal stabilizer trim actuator of the KC-135 is not connected to the same device being scrutinized in the crash of Alaskan Airlines Flight 261, which killed 88 people.

The KC-135 is decades older in its design and manufacture than the MD-83 that crashed off the California coast on Jan. 31.