_AW&ST_ had reported on this mishap-investigation in only two other issues of the magazine, during Apr'79.
Failure - Interactions
and citing early assumptions
as instead "findings"
… NTSB staff report’s author,
Leslie D. Kampschror, investigator in charge,
told the board at the open meeting June 9
that he had obtained
“no direct evidence” to prove that
the crew had manipulated the controls.
The staff used a process of elimination that
ruled out mechanical failure to conclude that
the crew must have taken
some action that extended the slat….
"The safety board ruled out . . .
because of complexities involved . . ."
Note the INVESTIGATORS' hidden assumption:
there were NO POSSIBLE
just prior to INITIAL upset.
As a counter-exemplar, where other investigators explicitly listed their assumptions,
and investigators considered
a possibility of a double-failure,
see the investigation of
Sabina B707 / 15Feb61 (bottom, causes)