Run-in
Run-in turns up in 2 fields: gears, hydrography. Here is what it means to the people in each one.
Run-in in gears
Operating new gears at reduced load at first so surface high spots wear smooth before full duty.
The initial period of operation, often in steps of increasing load, during which roughness peaks and small errors on new tooth surfaces wear or plastically flatten, improving contact and the oil film. A good run-in lowers the risk of early scuffing and micropitting. The first oil fill is often drained afterward to remove the wear debris it collected.
"Run-in at half load for the first eight hours, then dump the oil and change the filter before full production."
Run-in in hydrography
The stretch before a survey line where the boat settles on course and speed before logging starts.
The approach leg in front of each line. The coxswain uses it to get straight, at survey speed and on heading, while the motion sensor recovers from the turn and any towed sensor settles. Lines planned without enough run-in give ragged starts and wasted data. A launch needs a few boat lengths; with side-scan it is far longer because the fish lags well behind the turn.
"Give me a longer run-in on these, the fish is still swinging when we go online."