A helicopter circled above the Midtown Greenway on Tuesday afternoon as students waited below in the June heat. Two National Guard chief warrant officers disembarked to tell members of the Junior Police Academy about the Army’s work in countering narcotics. Chief Warrant Officer 3 Russell Motes, in town for an operations briefing along with Chief Warrant Officer 4 Bayne Walker, spoke about the qualifications needed to fly aircraft in the Army and about the National Guard’s efforts to eradicate marijuana.