[londons_explore]

Even redundancy doesn't really solve the issue. The sensors are out in the same environmental conditions, so will likely all fail at once, for example a bad pattern of water followed by cold causing icing.

Instead, the sensors should detect failure, for example by using a motor to detect if the vane is stuck and cannot turn freely.

The flight controls should also be able to fly even if all sensors of a certain type have failled. Angle of attack for example can be approximated with an accelerometer and gyro well enough to keep the plane in the air.

[dTal]

>Angle of attack for example can be approximated with an accelerometer and gyro

I'm prepared to be wrong but that sounds impossible to me. A steady-state descending stall is inertially indistinguishable from cruise.

[londons_explore]

You're right - you need to combine with altimeter or GPS, and for more accuracy you can also combine with wind direction forecasts or airspeed measurements.

The point is, there are lots of data sources, and with even a subset of them, it's possible to fly the plane to a safe landing.

[piva00]

But then the motor could break, and so it goes. The more moving parts around you have, the more failure modes you have.

[londons_explore]

If the motor breaks, the sensor has failed.

Failure isn't really the problem - it's silent failure which is deadly.