Why 2 black boxes? Why not combine them?

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Why 2 black boxes? Why not combine them?

Post by Y.. » Wed, 17 Nov 1999 04:00:00


       It seems to be that having two separate boxes complicates
recovery in case of accident.  I was wondering:  Why not have two
recorders housed in a single box?   Or even having all the data
recorded to a single tape.  This would also make it easier
to synchronise the data and voice recordings (they would be
in sych since they would be on the same tape).
 
 
 

Why 2 black boxes? Why not combine them?

Post by Rafael Kamp » Wed, 17 Nov 1999 04:00:00



>       It seems to be that having two separate boxes complicates
>recovery in case of accident.  I was wondering:  Why not have two
>recorders housed in a single box?   Or even having all the data
>recorded to a single tape.  This would also make it easier
>to synchronise the data and voice recordings (they would be
>in sych since they would be on the same tape).

Maybe it's just game for the recovery staff, or could be, on a more
serious assumption that in case one gets destroyed somehow there's
always the chance of the other one being in a good shape. Or maybe
it's a technical problem on which I cannot speculate.
 
 
 

Why 2 black boxes? Why not combine them?

Post by JF Meze » Wed, 17 Nov 1999 04:00:00



> Why not have two
> recorders housed in a single box?   Or even having all the data
> recorded to a single tape.  

Disaster tolerance. (computer terminology context).  If all are stored in one
box, and the box does not survive, you lose all. By storing in two separate
boxes (which I beleive is located at dirrent areas of the plane) you increase
the changes of having at least some data to help investigate.

However, with today's technology, I think it might be more disaster-tolerant
to use volume shadowing technology. Record the CVR and FDR on the same media
but record it on two separate boxes simultaneously. This way, both the voice
and flight data are duplicated so if one of the two boxes survives intact, you
get all the data.

 
 
 

Why 2 black boxes? Why not combine them?

Post by Mike Cordell » Wed, 17 Nov 1999 04:00:00


There was a story on one of the media outlets (either the paper or one of
the news magazines) that says the new variety of black box downloads it's
data constantly to the ground (probably via satellite) so that there isn't
any searching for it at all, the data is constantly coming and being
recorded someplace on the ground.  It said this technology isn't at all used
here in the states yet, but being tested someplace in Europe.

I would guess that the two are different because they are recording
different things (which is changing as they are switched to all digital
systems).  The voice recorder is a four or six track tape that is a half
loop that looks like nothing more then a glorified answering machine with a
pinnger on it, the data recorder seems to be recording so much more
information and would be incompatible with the voice stuff.


Quote:

> Disaster tolerance. (computer terminology context).  If all are stored in
one
> box, and the box does not survive, you lose all. By storing in two
separate
> boxes (which I beleive is located at dirrent areas of the plane) you
increase
> the changes of having at least some data to help investigate.

> However, with today's technology, I think it might be more
disaster-tolerant
> to use volume shadowing technology. Record the CVR and FDR on the same
media
> but record it on two separate boxes simultaneously. This way, both the
voice
> and flight data are duplicated so if one of the two boxes survives intact,
you
> get all the data.

 
 
 

Why 2 black boxes? Why not combine them?

Post by Mark Roger » Wed, 17 Nov 1999 04:00:00




> > Why not have two
> > recorders housed in a single box?   Or even having all the data
> > recorded to a single tape.

> Disaster tolerance. (computer terminology context).  If all are stored in one
> box, and the box does not survive, you lose all. By storing in two separate
> boxes (which I beleive is located at dirrent areas of the plane) you increase
> the changes of having at least some data to help investigate.

> However, with today's technology, I think it might be more disaster-tolerant
> to use volume shadowing technology. Record the CVR and FDR on the same media
> but record it on two separate boxes simultaneously. This way, both the voice
> and flight data are duplicated so if one of the two boxes survives intact, you
> get all the data.

That's actually a proposal currently under review: Combine both
the CVR and FDR into one unit, but have two separate boxes.

Also, to answer a previous question, the newest CVRs and FDRs
don't have any tape.  They record onto computer chips, and are
actually more resilient than tape.  The Simmons 4184 accident
(ATR with high impact velocity) had at least one solid state
recorder (no tape), and all the information was recovered,
despite the unit being crushed.

--Mark Rogers

 
 
 

Why 2 black boxes? Why not combine them?

Post by Ken Ishigur » Wed, 17 Nov 1999 04:00:00




> > Why not have two
> > recorders housed in a single box?   Or even having all the data
> > recorded to a single tape.

> Disaster tolerance. (computer terminology context).  If all are stored in one
> box, and the box does not survive, you lose all. By storing in two separate
> boxes (which I beleive is located at dirrent areas of the plane)

Not true.  On most aircraft, both boxes are mounted adjacent to each other on the
same equipment shelf.  (On a 747, for example, above Door 5L).

Quote:> you increase
> the changes of having at least some data to help investigate.

> However, with today's technology, I think it might be more disaster-tolerant
> to use volume shadowing technology. Record the CVR and FDR on the same media
> but record it on two separate boxes simultaneously. This way, both the voice
> and flight data are duplicated so if one of the two boxes survives intact, you
> get all the data.

I could stand corrected, but I think the issue is very simple.  FDR's were
required and developed long before CVR's became a requirement.  In the avionics
development business, if it works, don't futz with it.  It makes more sense to
develop a second box (CVR) than to modify a FDR.  Another point is basic
requirements of an FDR and CVR are different.  The FDR must hold many (24) hours
of data; a CVR needs to only hold 30 minutes.  Also, the systems which input data
to them are completely different.  Bottom line is you would end up with the
mechanical and electronic components required for both in the same box, with very
little commonality or "shared" components.

Lastly, in all the crashes I can recall, either both boxes were recovered, or
neither were recovered.  So two separate boxes doesn't seem to affect
survivability or recoverability, and actually improves the odds of getting data as
JF points out.

Ken Ishiguro

 
 
 

Why 2 black boxes? Why not combine them?

Post by Dan Larse » Thu, 18 Nov 1999 04:00:00



> That's actually a proposal currently under review: Combine both
> the CVR and FDR into one unit, but have two separate boxes.

> Also, to answer a previous question, the newest CVRs and FDRs
> don't have any tape.  They record onto computer chips, and are
> actually more resilient than tape.  The Simmons 4184 accident
> (ATR with high impact velocity) had at least one solid state
> recorder (no tape), and all the information was recovered,
> despite the unit being crushed.

Simmons... Not to long ago, that was A Eagle, right?  Just out of
curiosity, when did AMR purchase A Eagle from Simmons?

-Dan

 
 
 

Why 2 black boxes? Why not combine them?

Post by Dudley Cornm » Thu, 18 Nov 1999 04:00:00



>        It seems to be that having two separate boxes complicates
> recovery in case of accident.  I was wondering:  Why not have two
> recorders housed in a single box?   Or even having all the data
> recorded to a single tape.  This would also make it easier
> to synchronise the data and voice recordings (they would be
> in sych since they would be on the same tape).

All your eggs in one basket?

dsc - acssysdsc