> > AFAIR a classic example of what you described below happened with a
> > brand new Airbus prior to their mass availability.

A Foker-100 jet crashed seconds after the take off years ago, in the
middle of a S‹o Paulo (Brazil) 18 Million people city, a residential
place, school and everything else went in flames, burning fuel running
at the street... lots of cars and houses went to hell.  The problem?  A
simple air-brake system went open during the take off run.  (The
air-brake is the body of the engine that slides to the exhaust's back
and deviate the jet sideways (up and down) to create a braking air-flow
barrier). One engine was braking while another was pulling the airplane
forward. It created a terrible situation to the pilot that accelerated
to the extreme (since the plane was not gaining altitude), by the same
rate the air-brake was braking harder.  He deviated a school full of
children and landed over few houses and in the middle of a street. The
voice recording shows that maneuver. If memory serves, 80 passengers,
sadly no survivors. No electronics indicated to the pilot the problem
during the take-off run. A flight mechanic close to the runaway saw it
and crying desperately yelled "the brake is open, the brake is open, by
God somebody stop that plane..."  Lots of discussions went on, Everybody
said it could not happens, air-brakes doesn't open during the take off,
"there are several security systems", but, perhaps a simple positioning
switch connected to that brake panel, with a PIC blinking a LED at the
pilot's panel could save more than 80 lives.  If he knew what was
happening, even after the take off, he could just shut that engine off
and somehow make a safe landing at a close airport using just the "good"
engine.  The first big problem there was "lack of information". 

Years ago, a Boing 737 took off from a city close to the Amazon Forest,
destined to a city at the east, the pilot let the procedures to the
co-pilot. He did input the flight path wrongly, instead of 18.5 he
inputted 185 degrees. The control tower use not to say the decimal point
what confused the newbie co-pilot.  The pilot was reading a newspaper. 
The plane went over the amazon, dense forest. In half an hour was out of
any radar scanning. When the pilot saw the topology he not understood
what was happening and tried to solve the problem. The plane went deep
and deep over the Rain Forest, wasted all the fuel and landed in the
middle of the dense vegetation with some survivors, including pilot and
co-pilot, lots of killed by the seats jamming all together at the front.
A group went walking in the middle of the forest, reached a farm and
asked for help. Again, what a hell a GPS is made for? Man, if I were a
pilot, even if the plane has one, I would also have my personal $87 GPS
bought at K-Mart... Was the air traffic control people also wrong that
did not notice the airplane was going to a wrong direction? Perhaps a
PIC just checking few tables could notice the wrong input angle for that
lat/longitude and not only blinks a LED but also put the pilot pants on
fire.

As you can see, the first example is a classical mechanic failure, the
second, a terrible coincidence of several human errors, both could be
avoided with better use of technology.

Wagner