Failure - Interactions

... NTSB blames the extension on the crew,

but  does not go into detail  

about  exactly how  it happened.

... 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