Re: Automatic disaster beacons???

From:         shafer@ferhino.dfrc.nasa.gov (Mary Shafer)
Organization: NASA Dryden Flight Research Center, Edwards CA
Date:         19 Apr 96 02:04:03 
References:   1
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On 10 Apr 96 02:17:43 , ztomcich@mason2.gmu.edu (ZACHARY R. TOMCICH) said:

Z> I just saw the movie 'Alive' yesterday and was horrified that at
Z> the primative use of search plane to try to visible find the
Z> airplane wreck.

That's how you do it, particularly for VFR flights.  Ask your local
Civil Air Patrol or a SAR unit.

A lot of times, the first thing that indicates a problem is that
someone doesn't show up somewhere on time.  Filing a flight plan with
an accurate arrival time tends to speed up the process of realizing
that something's happened, rather than waiting until starting time at
work on Monday.

Z> Aren't planes equiped with automatic disaster radio beacons which
Z> will transmit in the event of an emergancy?  Since when were these
Z> implemented if they exist, and if they don't exist, why not?  How
Z> expensive could a small radio in a crash container cost?

Little airplanes have ELTs, Emergency Location Transmitters.  They
were optional for a long time, but because required some time in the
last ten years or so.

Ejection seats have emergency beacons for aircrew location and rescue.

Anything that flies in controlled airspace (on radar, in other words)
has to have an altitude-encoding radar transponder that talks to the
ATC radar to tell it where the plane is and how high.

Z> If an airplane does indeed crash, what it used to find its
Z> position?

For a plane flying in controlled airspace, they start from where it
disappeared from the radar screen and look along its projected path.

For an ELT-equipped airplane, they DF (Direction Find) the ELT signal
by triangulation.

In friendly territory, they track down ejected aircrew in a
combination of the two by knowing where it vanished off the radar and
in what direction, then working their way back up the flight path from
the smoking wreckage.  If they can't find the aircrew or communicate
with them on Guard (the e-seat survival gear includes a PRC-20, or
equivalent), then they DF the beacon.  In enemy territory, where the
aircrew is E&E-ing (escaping and evading), the aircrew helps by
talking the SAR people into the right location.

Z> Is there any possibility of 'alive' reoccuring?

Sure.  (Why do I think this isn't the answer you want to hear?)

All that needs to happen is that the ELT be non-functional (expired
batteries, impact damage, etc) or the airplane be in some sort of
radar shadow.  Or for the accident to happen in bad weather,
particularly at night, so the search & rescue folks can't find the
airplane until after the beacon batteries run down, particularly in
rugged terrain.

Planes are hard to find in unpopulated areas, in mountains, in
forests.

That airplane in "Alive" would have been easier to find if it had
caught fire--columns of smoke are easy to locate.

There was a guy flying his little plane VFR who crashed fairly near
I-15, in the mountains by San Bernardino a couple of months ago.  He
crawled down the hillside to a frontage road and was found by a CHP
officer.  No one knew that he'd crashed.  I suspect that the officer
thought he was a body that someone had dumped (not uncommon in the
less populated areas around a large metropolis).
--
Mary Shafer               NASA Dryden Flight Research Center, Edwards, CA
SR-71 Flying Qualities Lead Engineer     Of course I don't speak for NASA
shafer@ferhino.dfrc.nasa.gov                               DoD #362 KotFR
URL http://www.dfrc.nasa.gov/People/Shafer/mary.html