More on the F-100 crash

Date:         12 Nov 96 13:58:53 
From:         stephan@lac.inpe.br (Stephan Stephany LAC-CC)
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According to the Brazilian press:

After analysis of the CVR and DFDR it seems that
(I say "it seems" because it's not official yet);

- the crash was indeed due to the deployment of the
  right engine reverser during take-off and initial
  climb (it opened and closed four times);

- the crew wasn't trained to such an emergency, but
  this would not make any difference because any
  alarm related to "thrust reversers not locked"
  was inhibited during take-off and initial climb;

- as someone mentioned in another msg, the F-100 has
  a protection for in flight deployment of any reverser:
  the related engine throttle is cut to idle;

- the crew though that something was wrong with the
  autothrottle (previous incidents with autothrottle
  malfunctioning), disconnected the autothrottle and
  pushed the right throttle full forward (obviously,
  the left one was always full forward);

- the opening of the right reverser was due to an
  electrical failure: the relay that commands this
  opening was energized (they are trying to find out
  why). TAM did a modification recommended by Fokker
  concerning a specific wire of the reverser actuator
  relay, in order to avoid battery discharge when
  aircraft is grounded;

How to explain what happened? The right reverser was
deployed due to improper power-on of the relay, that
triggered the right-engine cut-to-idle protection,
the crew reacted by applying right-engine full
throttle and somehow this cycle was re-started
(right reverser opening and closing and so on,
 right engine from idle to full power and so on).
No way of controlling the airplane...  The correct
procedure would be shut down the right engine *if*
the crew knew the problem was the reverser deployment.

TAM will provide emergency training for accidental
reverser deployment, and remove the inhibition of
related alarms during take-off and initial climb.

What caused the problem is not known yet. It could
be faulty design, defective spare part, improper
maintenance, etc. The board in charge of the
investigations concerning that crash and Fokker
itself are working on that.

It seems unlike that any EMI (due to celullar
phones, etc.) may have caused the crash (the board
is not even considering that).

Stephan Stephany
stephan@lac.inpe.br
National Institute for Space Research
S. Jose dos Campos - BRAZIL