Why are the AOA sensors placed outside the aircraft? Why should the AOA sensors be placed outside the aircraft? Is it not the angle between the chord line of a wing and a vector representing the relative motion between the aircraft and the surrounding air, in which case, is it not possible to measure the AOA with a simple instrument inside the cockpit, which eliminates malfunction due to exposure?
No, it is not possible to place the sensors inside the aircraft, because the angle-of attack sensors need exposure to the surrounding air, in order to measure, as you mention yourself, "relative motion between the aircraft and the surrounding air".