http://www.mountainflying.com/Pages/articles/images/lri_probe.jpg
The original poster wanted to see a "how it works" diagram.
It would be very easy for such a device to produce an audible alarm at low d.p.
You could also heat ports to prevent them being blocked by ice.
Keep It Simple Stupid...
See also Lift Reserve Indicator:
http://en.wikipedia.org/wiki/Airspeed_indicator#Variations
http://www.mountainflying.com/Pages/articles/alpha_systems_aoa.html
http://www.mountainflying.com/Pages/articles/images/lri_probe.jpg
It does not use a vane and encoder, but can work without power...
There is lots of weather you can't fly into. It's all about control.
Inter-tropical convergence is bad because you or radar may not see it.
Enhanced Turbulence Radar (ETR) can see much more.
Even a small bum steer from the many sensors could have lead to loss of control of the aircraft...
Not any dopper radar.
They have altitude, ground speed and rate climb which sees the ground. This does not help keep it stable in the air, but you want to know where the ground is.
A Pitot tube is required to get actual air speed.
The radar to detect most cases of inter-tropical convergence...
Now its official: Pitot tubes
FAA blames air-speed sensors (Pitot tubes).
http://www.wired.com/autopia/2009/06/airspeed-sensors/
http://www.spectrum.ieee.org/blog/computing/it/riskfactor/faa-orders-airspeed-sensor-changes-on-airbus-aircraft-in-us-fleet
Much older aircraft had similar probs...
Weather is a simpler explanation than lightning
Lighting strikes of air-craft are common and foreseeable. Though it is
quite likely the system will be disturbed its computers should reboot
quickly and enough come up to provide quorum in time. Some one I know
who flies Airbus has had some...