Scenario: you are flying in clear weather with radar off. You then enter a thin haze layer that starts to slightly obscure the horizon. You then lose sight of the ground but can just about still see the horizon and the sky above.
Question: at what point before hitting the enbedded CB you can't see do you switch on the radar?
The radar should be on at all times in flight, or at least until path to touchdown and go around paths confirmed clear.
Do none of you remember the UK-bound charter flight a few years ago that flew into an embedded CB with resultant major damage to windscreens and leading edges? Learn the lesson folks, leave it on. MTBF is for others to worry about.
