(мор.) головний навігаційний засіб
navigational aid (NAVAIDs); aid to navigation (ATON)
junction aid (obstruction aid)
obstruction aid (junction aid)
aid to navigation (ATON)
floating aid to navigation
air-navigation aid
position and navigation unit / position navigation unit (PNU)
gunner's primary sight (GPS)
officer of primary responsibility
primary (fire) position
primary arm
primary armament
primary burn
primary control surface
primary sector of fire
primary high explosive
primary military occupational specialty (MOS)
primary mission
primary reserve
primary target
primary target line (PTL)
primary trainer
primary weapon
primary position
primary, alternate, contingency, emergency (PACE)
primary level training (PLT)
primary venturi
primary control surfaces
primary defect
primary cause
primary great circle spherical coordinate system
primary rainbow