Rhino    Unflattering nickname for the F-4 Phantom II.
RIO   Radio Intercept Officer -- The rear-seat weapons and navigation
    specialist in the F-14 Tomcat and F-4 Phantom.
ROE    Rules Of Engagement -- Rules governing the conditions under which
    a fighter can engage or fire upon an unidentified aircraft.
ROK   Republic of Korea, also known as South Korea.
roll   Movement around the longitudinal axis of an
    aircraft.
RPM   Revolutions Per Minute -- A measure of the amount
    of power being produced by an engine.  (See also 
    thrust.)
RSAF   Royal Saudi Air Force.
RSO   Reconnaissance Systems Operator.
RSS    Relaxed Static Stability.
rudder   A vertical aircraft control surface used to rotate the plane about its
    vertical axis, i.e., to turn it without banking.

SA-6 Gainful missile   A surface-to-air missile designed in 1967 and
    launched from SAM sites against aircraft flying at medium heights.  It is
    more effective than the SA-2, but can be fooled occasionally by ECM and