The pressurized sump, because of its dimensions, can only hold approx 6 qts. This sump is the "reservoir" for the system. The main, standby and aux pump, pull from this reservoir, pressurize the fluid and then the valve housing directs the pressurized fluid to the fwd or back side of the pitch change mechanism (dome piston). In simple terms, "what goes in must come out". The fluid comes out of the dome and into barrel. In the back of the barrel, moved by the #1 blade, is the beta feedback shaft. This shaft is hollow, which is the escape route for fluid in the barrel. When exiting the shaft, fluid is now returned to the atmospheric sump. The scavenge pumps suck it up and return it to the pressurized sump. With a basic understanding of how fluid travels through the propeller, let's address servicing. Remembering that the pressurized sump can only physically hold approx 6 qts, it is impossible to overservice this sump. Sure, you pull the cap to insert the dipstick and sometimes fluid WILL spew out, but this is NOT overserviced. As mentioned above, pressure may be slow to bleed off and fluid under pressure will rush towards the path of least resistance, ie. an opened toilet seat cap. Under operation, all supply pumps, internal passages, dome, barrel, etc are filled with fluid, not air. The only place that is not filled to capacity with fluid is the atmospheric sump. If a prop is truely overserviced, this is the only place for that extra fluid, hence the addition of the atmosphic dipstick. On a properly serviced prop, with the pumps operating, the atmosheric sump will have approx 17 oz of oil. This coincides with the mark on the atmospheric dipstick. During a service check, cycling the prop 3 full cycles is to purge any air from the internals. On the final cycle, with the aux pump never being allowing to stop, the atmospheric dip stick should be pulled, wiped, inserted and pulled to give an accurate reading. If the fluid is at the bottom 1/4" of the stick, your prop is serviced correctly. If its higher than that, your prop is overserviced. If there is nothing on the stick, your prop is low and should then be verified by checking the pressurized sump dipstick. Keep in mind that after performing major prop maint, such as prop change or dome removal air will usually will be locked in the system until a run is performed. Centrifugal force and the combined 60 QPM flow of the main and standby pumps will remove the air and often give a "low oil" light during the run. That is why, following tech data, a service check is required after the first run. This is the "nuts and bolts" version of proper servicing. There will always be potential variables, such as acft lean, aux pump condition, internal leakage, clogged orfice cups in the pitchlock regulator, and so on.
