So his was on before take-off and obviously looking up. Is it like a transponder .. turn on when entering the runway ?
It is turned on or off whenever the pilot wants it in the on or off position. If the weather gives cause for concern then it is switched on and on our Airbus type the tilt is initially set to 5 degrees up pitch unless it has the newer auto tilt function which sets the tilt angle to optimize the weather radar detection.