I have seen multi copters and helicopters UAV used for crop dusting. But I have never found any fixed wing UAV used in this area. As different countries have different farmland size and regulations, totally lack of fixed wing in this area seems to be strange.
Could anyone explain that’s why?
In thinking about the specific operating environment these are/will be used the two limiting factors to fixed-wing are;
Lack of suitable airstrips to actually land, taxi up to the truck, reload, and take back off in a rapid fashion. Hand launch and skidding into foliage on the belly will not be practical for the high cycle operations of aerial application. Larger equipment will be needed before the wheel size will overcome some of the potential landing surface shortcomings.
Limitations due to LOS requirements and operating environment. If you youtube some of the RMAX videos from Japan you'll notice that they are in very confined area's and don't actually turn outside the field at the end of a pass. They just slide over to the next swath on the end of the field, sometimes not even changing direction of the vehicle, and come back the other way. Certainly more efficient time wise, less liability in high density area's with houses on the edge in the event of a trailing nozzle or a malfunction of the spray shutoff valve, and easier for the operator to perform because there are less items for him to judge being that he is not trying to judge a pull-up, distance from trees on the climb out, turning over the tops of obstacles, judging the distance to the trees again on the re-entry to the field, and judging the flare out at the bottom and the turn on.
Certainly all things that happen full sized but with the eyeballs inside moving with the vehicle, with the ability to see any point of almost an entire 360 degree field of view at any time we see fit to make a distance judgement.
VTOL vehicles that can stop all forward movement will be the best choice for this unmanned application for years to come.
No matter the vehicle type though, I am still waiting to see an unmanned vehicle land, load, and take back off to put out another load repeatedly, multiple times, without stopping. As occurs in full sized aerial application.
The majority of spraying via small aircraft or UAV is done by line of site in small acreage patches (See how the Yamaha Rmax is deployed). In this application the advantages of being able land vertically outweigh the efficiency of a fixed wing aircraft. If we are ever able to surgical applications outside of LOS then I think you'll see the fixed wing come more into play. The other aspect is that in agricultural spraying the downdraft caused by rotors is an advantage because it reduces spray drift and increases coverage. (Cherries can actually be dried off after a rainstorm by large rotor aircraft so that they don't spot or split) in a fixed wing aircraft the aircraft speed and the turbulence of the prop wash come into play in breaking up the droplets and having them fall into the crop canopy so spraying with a fixed wing has a few more factors that come into play.
Purdue University, UAS.
I don’t understand why the flight speed is limited by the auto spray trigger. If it doesn’t spray fast enough, why not use a stronger pump?