The F-4’s AN/APR-25 & 26 Radar Homing & Warning System

The radar homing and warning system (RHAW) was a very important black box installed in F-4s that flew in combat in the Vietnam War.  The device gave crews audio and visual input whenever a radar beam struck the Phantom.  The three main components of the RHAW system were the threat display unit (TDU), the round cathode ray tube (CRT) and the audio sounds the RHAW system made in the headset.

The TDU was a small rectangular box with two rows of lights.  When a radar beam struck the F-4 the frequency of the beam caused a light on the TDU to illuminate with the type of radar.  For example, the light might be AAA for a gun radar or AI for a MiG radar.  The lights nobody wanted to see were the two flashing lights that said MISSILE and LAUNCH.

Each type of radar also caused a tone to be played in the crew’s headset.  The pitch of the tone varied depending on the type of radar beam that struck the Phantom.  Crews could determine the type of radar by the pitch of the tone.

The CRT was a round little TV screen about the size of a travel alarm clock.  This device displayed three items of information: (1) the type of radar beam that hit the airplane such as a solid line, a dashed line, dots or a line and dot, (2) the relative strength of the radar by the length of the display, and most importantly the clock position of the radar.  If the display was a solid line from the center of the screen going towards 6 o’clock the radar was at the 6 o’clock position.

There was also a little red light at the top right of the CRT that had the letters A/S to the left of the light.  The A stood for “azimuth” and the S stood for “sector.”  The SA-2 control van had several radars on it.  One radar went left then right, back and forth.  Another radar went up and down repeatedly.  The A/S light would illuminate if the F-4 was in the intersection of the SA-2 surface to air missile (SAM) left and right (the azimuth) radar and its up and down (the sector) radar.  To track an F-4 the target had to be in the intersection of these two radar beams.  We called the A/S light the “awe shit” light because if it came on it meant the bad guys were about to fire a 35 foot long supersonic flying telephone pole at the F-4.

Watch the video to learn more about this life-saving black box.

P.S.  Some guys in my squadron would fly into Route Pack VI with their RHAW gear turned off because they said it created “information overload” and could distract from radio traffic and situational awareness.

2017-09-27T16:01:27+00:00 By |0 Comments

About the Author:

Rick Keyt has practiced law in Arizona since 1980. He flew the F-4 Phantom for five years in the United States Air Force, including combat missions over South Vietnam, North Vietnam and Laos in 1972. For more about Rick's bio including his F-4 bio see his resume on his law website. Connect with Richard at 480-664-7478 or on Google+

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