In order to maintain battle readiness, the flight deck fueling crew must perform with speed and efficiency. A delay in refueling can render pilot and aircraft exposed and vulnerable. Under a battle alert, such a glitch could compromise a mission and even the defensive posture of the carrier itself. To prevent this, the flight deck Fuels Chief trains and supervises his flight deck fueling crew relentlessly. Under his vigilant eyes, the fueling crew known as the "Grapes" because of their purple shirts squeezes out the 'juice' to refuel an average of 140 to 150 aircraft every 16 hour workday. In daylight, it's hazardous duty that requires focus and total attention to detail; at night, in total darkness, the job can be perilous. Besides fueling and defueling a wide variety of aircraft, the flight deck Fuel Chief is responsible for the smooth operation of the fuel systems, pumps, filters, and even the catapult lube system.