250 ft!! We'd get a nose bleed.
Usual to operate at low-level by day between 75-125 ft as that is the most comfortable height to fly at in the UK due to wires etc, however, the RAF are cleared to 50 ft in transit by day and I think the RN/AAC are similar (maybe 100 ft). UK Mil helos can also conduct concealed approach and departures down to a minimum of 3 metres from obstacles.
What is the safety problem? We're trained to do this right from the offset and since the majority of low-flyers are twin pilot or pilot/nav manned it is actually easier than it looks.
HPT