second echelon maintenance

echelon-to-echelon communications system

first echelon maintenance

first echelon medical equipment maintenance

echelon maintenance

third echelon maintenance

fifth echelon maintenance

contingency maintenance / special maintenance

depot maintenance (beyond O and I level activities, performed in an industrial-type facility) / D-level maintenance

maintenance checks / routine maintenance, scheduled tasks

maintenance idling (periodic running of engine for maintenance purposes)

organizational maintenance (O-level) (day-to-day work that standard airfield maintenance groups perform in support of airfield operations)

routine maintenance / scheduled tasks, maintenance checks

scheduled tasks / routine maintenance, maintenance checks

special maintenance / contingency maintenance

meters per second (m/s)

second in command (2i/c , 2IC)

second lieutenant

second order effect

floating-point operation per second (FLOP)

captain second rank

fuel flow (kilogram/second)

centimeter-gram-second (CGS)

meter-kilogram-second-ampere system (MKSA)

meters per second (MPS)

second cause

second mean chord

additional second lieutenant

second-trip echo

second wave attack theory

second classman

second commander

second for service