Grass removal

The day before graduation from army basic training, I stood on the edge of a blazing hot parade field watching a group of soldiers rake the freshly cut grass. Suddenly, a helicopter appeared and made a practice landing in anticipation of delivering a dignitary the following day. The sergeant in charge of the ranking detail ran to the cooper and spoke to the pilot. He jogged off the filed, taking his group with him. The helicopter lifted off, made a few low passes over the field, then flew away. I asked the sergeant what manoeuvre the pilot had been practicing. He smiled and said, "Grass removal."