... flight data recorder ... proved ... unhelpful ...

"... Pilots Association ... ALPA  blamed pressure from Boeing for   NTSB's  rejection of  possible mechanical causes . . .  advanced  its own hypothesis:


a worn and misaligned leading-edge Slat  popped out . . . roll to the right."


Garrison  accurately cites  ALPA's  later   joining   the  investigative-focus on  the separated   #7Slat:  


Mistakenly,  the Pilots' Association  did  NOT  challenge  that erroneous  assumption --

  a  Slat EXTENSION   just prior to INITIAL upset.   


Both the NTSB-staff  and ALPA -investigators  had failed to  

call-into-question  that erroneous assumption,  that   red-herring,   asserted by the manufacturer,  in their first

draft of   the Boeing Scenario   dated  August 21st, 1979.

NTSB's  P.C.  =   the Boeing Scenario.

An NTSB Err -- there is nothing in the direct evidence to support the erroneous assumption that "passing through 21,000 feet ... landing-gear extension"


Damage to  components near  the RHS-MLG, together with  Trail-of-Debris,  and  Trajectory of Separated Parts,   shows proper altitudes for these LG-EXTENSION  failure-interactions.

The erroneous assumption:

"... the slat in the EXTENDED position ...

initially caused the airplane to roll  . . ."

... analyses ... will remain in

the realm of supposition.

The NTSB version . . . 

"These reports,  although mentioned by one aviation publication . . ."


Yet,  other aviation-publications,  and general media,    did  allude to these   vague  rumors  about  this previously  non-existent,  unheard-off,     "procedure" --  this rumor was an assumption,  the NTSB labeled the rumor  as   "a finding",  and   the rumor was part of  NTSB's P.C.​

The vague  rumors  shortly   AFTER the mishap,


     The Boeing Scenario,


 the NTSB's  "findings".

B-727,   N840TW,   TWA841 /  4Apr79,   CRZ,  night,  Saginaw,   mysterious  inflight upset,  Yaw x Roll = DIVE,   Loss-of-Control, pilots' EXTENDED Landing Gear,   fortuitous hydraulic-failure of System-A,       recovered control,   5.8-G pull-up, diverted to DTW.

Garrison's   faith in  NTSB-method:

he thus missed  explicitly specifying  the weakness in the USA's  system of   investigation:

 

The USA- method   relied on the manufacturer,  or the   pilots' association,  to help provide   NTSB with  the  complex  failure-interactions.


   The pilots' association had erred, by not challenging that  distraction, that "red herring"  --  that mistaken  assumption,  that  an EXTENDED- Slat  was a "cause" of initial upset  (mistakenly  accepting an erroneous  linear failure-sequence).   

Yorke  later showed  investigators that    accepted practice was to "work backward",   focusing on DIRECT EVIDENCE:  working  from the Trail-of-Debris, Yorke offered the needed insight:  

that an un-commanded  

 Slat  EXTENSION-separation   

was a later "effect" --  unrelated to  causes of the INITIAL  upset  at CRZ FL390.

"In fairness . . .  

while this explanation is now the official one,

the NTSB  . . . claims . . .  that

alternative mechanical explanations are

too remote and  improbable . . ."

"... might be called Gibson's Law,  

and it deserves to be burned into the memory of all pilots . . .  who find themselves plunging   out of control   toward the ground at night:


never give up."

Garrison's   editorial  comments,    & his review of NTSB's  investigation,

 and    AAR-81-8.  

From   Flying  magazine,    March 1982,    pages 94 to 96.

Garrison, Peter.    "Aftermath:   In Quest of  Extra Performance"  

Flying Magazine.  109:3 (March 1982),   p94-6

Failure - Interactions

... NTSB blames the extension on the crew,

but  does not go into detail  

about  exactly how  it happened.