It would have to be one of the best videos on youtube, its one of the best that ive seen. Does anyone know if you are able to download that video. Depending upon what aircraft, weight, and whether you are spraying or seeding, Seeding is generally much slower, I have some typical working speeds of the Air Tractor series from their brouchure.
The AT401B is a radial type engine - 193-225kph, with the larger AT802A is 209-257kph. The 802 is a turbine engine type. The chemical is stored in the nose section in most ag planes, just behind the engine. Although some ag planes store it in the fuselage area.