If all the painting
clouds are below the level of the aircraft the lowest scanner tilt angle that
would show a clear screen is the one that has the base of the beam level. F
or a 5º beamwidth
this would have the centre of the beam 2.5º up.
It follows from this
that, if there were any clouds painting, their tops would be at or above
aircraft level - hence the slightly odd wording of the question