ATC will often ask pilots if they can do something somewhat out of the ordinary for the purpose of granting a shortcut or maybe to gain that extra slice of airspace. This subtle word works on both sides of the coin. In the pattern, Tower might ask a pilot to fly a short approach that-if the pilot is unprepared and accepts it-requires a steep and fast dive. Perhaps youve been offered that so they can fit you inside of other traffic, to avoid vectoring you 10 miles out to get behind everyone. Or, perhaps they just need you to cross the approach end of the runway so they can start getting other airplanes out. Regardless, if you dont think you can safely and properly comply, bring on the PIC authority and just say it, Unable.