Re: 757 flight recorder located

From: (Chuck Totman)
Organization: Hewlett-Packard Mayfield Site
Date:         14 Mar 96 17:49:29 
References:   1 2 3
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Jon Ward ( wrote:
:   "John Bay" writes:
: > Would it be possible to make a flight recorder that would transmit all its
: > stored data upon request, thereby eliminating the necessity to physically
: > recover the box?

: I may be wrong, it's a while since I did my electromagnetics course...

: The problem is sea water. Sea water contains sodium chloride (and various
: other things), and this makes it an electrolyte - it can conduct electricty.
: Because it conducts, this makes it harder for electromagnetic radiation
: such as radar, radio transmissions and gamma rays to penetrate

<snip out section here>

: There is also the question of weight - adding a transmitter to a black box
: (and batteries) which can survive a crash or explosion means extra pounds.
: Every flight you take when it doesn't crash costs you money.

<more snipped away here>

What you are proposing is telemetering the data, either real-time or
after a crash.  On land, this is probably best done with radio waves.
In the water, the best option is probably acoustical.  (I used to work
with some simple acoustic telemetering in the ocean about 20 years ago.
It works great.)  Either approach would require that a significant
collection of equipment still be functional after impact, explosion, fire,
submersion, whatever.  And you'd need radio for land crashes and acoustic
for water.

That would be expensive both in terms of weight and cost.

Right now, nothing must operate after a crash.  The tape (wire?) is
recovered and then taken to a full laboratory for the analysis.

The real-time telemetering for any particular aircraft is certainly
technologically feasible.  But the amount of data from each flight times
the number of flights in progress at any one time combined with the
distances from land-based receiving equipment could present significant
data collection and communications challenges if real-time telemetry
were mandated for all (or even all big) commercial flights.  I suspect
it will come within the next 3 to 5 years.

Chuck Totman            *******************************************
                        * Views expressed are mine alone and do   *
                        * not represent the views of my employer. *