Failure - Interactions

Limited  Strength  of   an

      Extended   Slat

Three months  after 

     two  Board Members  endorsed 

        The  Boeing  Scenario

           as their official   P.C.

             in NTSB  AAR-81-8 ,

then  another  outboard Slat

  suffered  a  loud explosive  


First Flight  of   B-767  VA001,


during  the otherwise normal 

      flap-slat configuration

for   approach   to Boeing-Everett,

           Paine Field.

A flight test  mishap  never reported,

    described  over  company radio

by the pilot of the F-86 chase-plane.

In fiction,   an   unreliable  narrator  

 tells the reader a story   

 ...  one of the most powerful tools available ...

The phrase   “unreliable narrator”   was

first used  in the early 1960s.    

The   technique   has been around

as long as literature itself . . .    

Hitchcock   termed  this  writers' tool

"a  MacGuffin":              

     "but there are no lions

in the Scottish Highlands."

. . . the most important thing to remember

about    the MacGuffin  is that

it contains  the word   “guff,”

which means  a load of nonsense.

 . . .  writes Spoto,  “but watch out for

the  MacGuffin.      

It will lead you nowhere.”

The Final Paragraph

included all

  seven steps

shown above.


     The investigator's    View through his paradigm

   a preliminary  conjecture,   from the manufacturer

        was  the NTSB Lead-Investigator's  favored hypothesis.

 An excerpt from the Boeing Report, pgs 3 & 4, Summary section:  the internal draft copy  by Boeing's R.A. Davis is dated Aug 21 '79;  formally sent to NTSB dated 24Sep79.  NTSB's IIC Kampschror  had requested Boeing's conclusions  during a June 6th meeting with R.A. Davis.  Later, since this early "analysis" from Boeing violated the NTSB's  explicit prohibition against  any premature speculation about "cause",  Boeing later requested that the first four pages of that Boeing Report (24Sep79)  be removed from the public record.   The NTSB's IIC didn't invite the other parties to submit any analysis-conclusions  until AFTER the field phase of the investigation, after the Tech' Review:   Only then, in a letter dated Nov'21st 1979,  the NTSB's IIC invited the pilots' association to submit ALPA's "recommendations on the conclusions to be drawn from the evidence" [letter from  NTSB's Kampschror to ALPA's McIntyre, dated 21Nov79].


So,  if  not  at  39,000 Ft,

? --  then  WHEN  would   a   L.E.- Slat be

pulled from the Retracted  position??

B-727 OMB 75-6   had  revealed

the   combination   of conditions

that   had   caused

unexpected    Slat   EXTENSION-separation

  The Boeing Report presented the         FDR-data,  and the  Parts Trajectory.

   The Boeing Report hinted at the next step,  but didn't explicitly offer this overlay of the two profile views. 

    NTSB's  AAR-81-8  simply omitted 

        this  step from  their analysis of

             the failure-interactions.

 --    Overlay  of Profile Views    --

Recovery Pull-up   overlaid  on Parts Trajectory

Trail of Debris, NE - SW, mile long, click for better image.

The    Direct Evidence   establishes

the   boundary conditions  for   a   Failure- Sequence.

Wreckage Examination --    The  mishap- B727   parked   on  taxiway at DTW

Trail of Debris --   Separated parts found in farm-field,  NE-SW mile-long trail

                     The Trajectory Analysis  works-backward  from this Trail of Debris,   offering  the possible  airborne profiles  of separated components.

Flt Recorder Data --   Heading   during   INITIAL-upset,

Then    Altitude,    Airspeed,    G's  

                        useful in  deriving Profile View  of the Recovery Pull-up.



Lesson  for  investigators:

? Sequence ?

 ?  Is  this  missing component   an    AFTER- effect? 

-- A   distraction?  

Or   Maybe    "the Cause" ?

The mishap aircraft suffered  the subtle  INITIAL  slice-to-vertical  Yaw x Roll   upset

at   FL390;  


     --  then a second protracted  phase of   uncontrolled  yawing-rolling  high-speed DIVE  from 39,000 Ft  down to  the final  recovery;

            --   AFTER  pilots  repositioned the Landing Gear Lever to the DOWN position, then followed the controlled  high-G  RECOVERY  phase.

Aft   --  looking  forward

RHS   O/B  Wing  -- Missing #7 Slat

Glines' story -- Continued --  from pg 11 of  the Oct' 1981 issue

The Boeing Scenario

from the Boeing Report  submitted during late summer 1979

Draft Aug79 The Boeing Scenario

Lessons from the Boeing-driven  


Night   FL390   CRZ    Yaw x Roll = DIVE

B727   N840TW,   TWA 841 /  4Apr'79