"John B." wrote in message
...
On Wed, 22 Feb 2017 20:39:46 -0800 (PST), Garrett Fulton
wrote:
....
Well, I was an airplane mechanic too and if I remember all the
instruments has colored marks on them to tell the Engineer when the
oil pressure (for example) got too low :-)

As for the guys in the front seats, they had a big loud warning
bell,
buzzer. siren, to tell the drivers when they slowed down too much
:-)
--
Cheers,

John B.

The Air France crash in the South Atlantic is a good example of the
difficulty of predicting in advance what warning the operator should
be given while their attention is on controlling the vehicle. Too much
or misleading info can be worse than not enough.

http://www.flyingmag.com/technique/a...air-france-447
"At one point the pilot briefly pushed the stick forward. Then, in a
grotesque miscue unforeseen by the designers of the fly-by-wire
software, the stall warning, which had been silenced, as designed, by
very low indicated airspeed, came to life. The pilot, probably
inferring that whatever he had just done must have been wrong,
returned the stick to its climb position and kept it there for the
remainder of the flight."

I read the CVR transcript in French and it supports the article's
conjectures. The airliner descended approximately level in or near a
Deep Stall, relatively stable in nose-high pitch but not in roll,
which kept the cockpit crew fully occupied and confused about what was
happening. The flight controls had less than their normal effect and
the engines showed the expected full power RPMs though they weren't
receiving the airflow to produce the corresponding thrust.

The pitot tubes had iced up in the storm's rising (super?)saturated
air and given the pilots and flight control computer incorrect low
airspeed values, initiating the problem, then probably soon thawed and
showed similar correct low values of forward airspeed because by then
the plane had gently stalled in Coffin Corner and was falling mainly
downward, its forward indicated airspeed below the stall warning low
cutoff until the captain tried nosing down, which was the proper way
to break out of the stall and regain airspeed and control.

Similarly, a NASA engineer told me the inside story of Neil
Armstrong's computer "failure" during the moon landing. The computer
serviced all inputs in a program loop. There was a warning light kept
Off by a hardware watchdog timer that the program would reset on each
pass unless it hung. The timeout was comfortably long enough in all
preflight tests but during the moon landing some added tasking
extended the loop beyond the timeout and allowed the warning light to
flicker On before the end of each loop pass, which Armstrong
interpreted as the failure it was supposed to indicate, not just an
unexpectedly high workload.

I knew something of the issue from designing industrial control panels
and then watching mindless UAW drones misuse them. I learned that
controls had to be not only idiot-proof but vandal-proof. Although I
had no design input on the aerospace electronics I prototyped I paid
attention to the discussions about their possible effect on cockpit
situational awareness. There was a joke circulating at the time that
the automated airliner cockpit of the future would contain a man and a
dog. The dog was trained to bite the man if he touched the controls.
The man's only task was to feed the dog.

-jsw