Abstract: A spreader unit is provided for connection to a hopper carried in an airplane for spreading granular material at a controlled rate of flow. A moveable gate on the spreader is moveable between a closed position covering a discharging opening through which the granular material may flow and an open position defining a gap to allow a predetermined flow rate of granular material from the hopper. A new and improved adjustable control 70 is provided in the cockpit of the airplane adjacent the pilot for manipulation by the pilot to control the gate width to an accurate degree to provide the desired flow rate despite deflection or other binding or lost motion in the linkage or levers in the actuating means for the gate. The control is positioned on the spreader adjacent the gate and a spreader extends from the actuator into the cockpit. A turnable handle is positioned adjacent the pilot for adjusting the size of the gap and thereby the flow rate of the granular material from the hopper.