Bruce Palmer wrote in
. net:

If this was the case with Columbia would it have made a difference?
"... in unusual situations such as an emergency landing, an actuator in
a crucial position could fail if it had upside-down gears."

In Columbia's case it probably wouldn't have made a difference given the
severity of damange to the left wing, but nobody really knows.

Nope, it can be said for sure it would not have made a difference. Columbia
broke up at Mach 18, long before the RSBs become active.

Last but not least... since "... the No. 4 actuator doesn't bear a
particularly heavy load", and Discovery has flown many times without
incident, it makes you wonder if the #4 actuator was necessary at all
from a design standpoint.

It is, if you want a design that has *margin* in it.

--
JRF

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