"SteveM8597" wrote in message
...
A non flying software engineer friend of mine insistes it is
poossible to put
devices on a plane to make it safer by impacting the ground at a low
velocity
after loss of control or catastrophic failure, or to be able to
manuever to
miss an obstacle when impact is imminent. These devices would
include
retrorockets, large recovery chutes, airbrake type control surfaces,
warpable
wings, and software on airplanes.

The world is full of technical experts whose education has assured
them that something was impossible only to be latter proven as wrong.

My qualifications are in controls engineering. In favour of your
friend let me say that now we have accelerometers, rate gyroscopes,
tiltmeters and inclinometers as well as single chip radars. The
devices are called MEMS (micro mechanical systems) these mean that
we have the sensors and intelligence to do at least part of what your
friend says on a single printed circuit board. We will know the
attitude of the aircraft and the rate it might be spining, how far of
the ground it is and how fast it is approaching even from the radar
what type of terrain and objects are in it.

You will note that BRS ballistic recovery systems
http://sbir.gsfc.nasa.gov/SBIR/succe...1-005text.html has
developed a parachute for the cirus SR20 light aicraft.

So at least for light aircraft you friend is right!

As an aeronautical engineer you might be able to research whether
there are any inherent limitations to the size of a parachute cannopy.
From what I can see about 16 sqare meters of canopy are required for
each 100kg. If we wanted to recover an empty 80 ton C-17 or M1
Abrams Tank we would need around 4000 sqaure meters which seems to me
to be about a 70 meter diameter cannopy (230 feet)

I do not know if there are any physical law limitations to parachute
scaling. Could we recover a large aircraft like a C130 Hercules, use
this as a form of STOVL or deliver a medium or even heavy tank?

Certainly the Apolo command module chute system seems to indicate that
at least 25 tons or so is feasilble and the way the Russians use a
reto rocket activated a meter above the ground indicates that a
landing can be cushioned.

Parachutes can ofcourse also be steered.

A vietnam UH1 Iroqois pilot in the RAAF told me they were not to
concerned with loss of the tail rotor in forward flight. It was
merely a matter of autorotating with the natural forces of the forward
flight on the tail boom straightening the aircraft and making a
semi-controlled landing possible.

I've often wondered whether is would be possible to recover an
aircraft such as a Blackhawke whose main rotor had been destroyed or
even lost a complete rotor blade.

A basic system would consist of a heavily armoured contol system which
which would contain a single chip based system of gyroscopes and
accelerometers.

When activated the system would fire series of retro rockets to right
the vehicle in both a crashworthy attitude or an attitude in which a
stabalising drogue chute can be deployed by rocket. Befor impacting
the ground a reto rocket can be fired. The drogue chute can be built
into the rotor hub for instance.

More sophisticated systems might be able to use explosieve bolts to
release damaged rotor blades or even eject the whole rotor,engine,
gearbox package (thus minimising the damage casued by rotor blades
flying of)

Even without a drogue such a system by putting the stricken chopper
into a crashworthy attitude could save a crew whose chopper was
damaged close to the ground.

The retro rockets would have to be designed. Gas pressure delivered
hypergolic propellants would work but this is probably likely to add
danger. A 25kg turobjet could deliver 250kg thrust and a pair of
these might be enough.

The controls might consist of several independent systems all
independantly capable of control and networked via multiple pathes.
Even if the pathes were destroyed the system could be capable of doing
its job.

As far as making an airliner recoverable you would have to decide if
the several tons of system to do this would not be better spent in
other areas.

The particular car I drive has the best breakdown record of any car
mainly because of its oversized battery.

The military might find such technology more usefull.

Ballistic recovery systems have had
successes on light planes and ultralights Otherwise, I have told him
that the
above have been proven to be impractical and even dangerous.

What is impracticable about them in larger vehicles. Be precise.