Not too unusual for military helicopters. In my day the book limits were 6 / 3 / 2. That was the closest we could fly in metres above / alongside / below the aircraft. The limits were really designed for crossing under wires because a) our job required us to fly "VFR" in really bad weather and b) Air Control orders sometimes didn't allow us
above 150 ft agl, to give us some separation from the many fast jets who were cleared to 250 ft agl. If we couldn't go over or around we went under.
We were
supposed to go under such obstacles at hover taxy speeds though. Once, a long time ago, having recce'd and crossed under going one way, I did it again the other way at cruise speed and scared the life out of my poor crewman. It was more than a bit silly in retrospect and did promise him I would never do it again - and I didn't. And good to his word, he didn't thump me, either.
