NASA finds flaw could have jeopardized Discovery
Tue Mar 23 07:58:09 2004
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CAPE CANAVERAL, Florida (Reuters) -- NASA has discovered a potentially disastrous mistake made more than 20 years ago on the space shuttle Discovery and plans to replace key parts on all three of its shuttles, the space agency said Monday.

Gears were installed backward on the speed brakes in Discovery's tail section and could have failed under the stress of an emergency landing, said William Parsons, the shuttle program manager.

"The bottom line was, it was not good," said Parsons, who told reporters the Discovery had flown safely 30 times since 1984 without the gears causing a problem.

The most likely scenario for a disaster would have come if the shuttle had needed to make an emergency landing at the Kennedy Space Center in Florida after an aborted launch, when the aerodynamic stress on the gears would have been greatest.

The reversed gears were found in an actuator that works the speed brakes, which are essentially flaps that flare out from the tail section to create aerodynamic drag and slow the shuttle. Small cracks and some corrosion were also found, surprising NASA engineers.

After the original actuators were replaced, NASA also tested extra replacement parts built 17 years ago, and found that one of the spare actuators also had the gears reversed.

Contractor error
Discovery is NASA's oldest remaining shuttle after the loss of the Challenger in 1986 and the Columbia in 2003. It has been chosen as the first craft to resume flying once the post-Columbia suspension of shuttle missions ends.

That Discovery mission is scheduled for March 2005, and Parsons said the added work would not necessarily cause a delay.

Parts are being stripped from the newer shuttle Endeavour to be installed on Discovery, but eventually NASA said it will have new parts on all three remaining shuttles. Atlantis is the third.

Parsons said the fault had been traced to the installation by a contractor, Hamilton Sunstrand of Rockford, Illinois, which had reviewed its procedures and found there was nothing to prevent the gears being installed backward.

"Yes, I'm surprised. It's a process escape that shouldn't have happened," said Parsons, who became the shuttle chief after the Columbia disaster and has overseen the $250 million return-to-flight effort.

"Hamilton Sunstrand has found new ways to do this. This won't happen again," he said.

Increased inspections
The company's program manager for the parts, Rudy Valdez, said the actuators are configured in mirror-image pairs, but the gears themselves are identical and were inserted one of two ways depending on which side of the pair was being built.

Hamilton Sunstrand has changed the fixtures used to assemble the actuators so that now each gear can only be inserted one way, Valdez said.

"We want to make sure it's mechanically impossible for it to happen again," he said.

The company has also increased inspections and implemented digital photographing during assembly to document that the parts are configured correctly, he said.

Hamilton Sunstrand is a unit of United Technologies Corp.

I found this posted on the "Plane Talking" forum @Hyperscale. Makes one wish for the good old days of Apollo. These guys can't seem to do anything right lately.