so we picked up an agras t40 earlier this season and overall its been solid but weve been having this annoying issue where the flow rate starts dropping off about 8-10 minutes into a mission, like it'll be set to 3.2 L/min and slowly creep down to 2.4 or lower and then sometimes recover on its own. nozzles are clean, filters are clean, weve checked all the obvious stuff. tank pressure seems fine on the ground.

wondering if anyone else has seen this or if its something in the mission planning settings. were using the agras app with terrain following on and the fields arent particularly steep so i dont think thats causing it. really dont want to send it back to DJI if i can avoid it, lead times on repairs have been rough lately

had something similar on a t30 a while back, turned out to be a partially blocked inline filter that we somehow missed on inspection, it would pass a visual check but under load pressure it was restricting enough to cause exactly that kind of gradual dropoff. try swapping the filter entirely even if it looks clean and see if that changes anything. also worth checking if the pump impeller has any wear, those can degrade and cause inconsistent output especially partway through a tank when the viscosity of whatever you're spraying changes slightly

is your battery voltage sagging under load? i know the t40 has a pretty robust pump system but ive read that if the batteries arent in great shape the pump can get inconsistent power delivery and behave weirdly. probably not the issue if your batteries are new but worth checking the cell voltage logs in the flight data. also what are you spraying, some adjuvant mixes can gunk up way faster than water alone even with filters