This post-1965 black and white informational film from the International Civil Aviation Organization (ICAO) explains the basics of secondary radar and illustrates its use in flight navigation and air traffic control using a combination of live-action footage and limited animation (TRT 23:09). It focuses on Secondary surveillance radar (SSR), a radar system used in air traffic control (ATC), that unlike primary radar systems that measure the bearing and distance of targets using the detected reflections of radio signals, relies on targets equipped with a radar transponder, that reply to each interrogation signal by transmitting encoded data such as an identity code, the aircraft’s altitude and further information depending on its chosen mode. SSR is based on the military identification friend or foe (IFF) technology originally developed during WWII, therefore the two systems are still compatible

Opening titles: “The International Civil Aviation Organization Presents Secondary Radar SSR” (0:06). Jet airliners landing and taking off from airport runways (0:23). Air traffic controllers. One speaks into a radio while viewing a radar monitor (0:56). Animation illustrates a radar signal spinning clockwise as an airplane passes from left to right (1:13). A radar screen shows two circled blips. A hand in silhouette circles another (1:37). An illustration shows the path of a radar signal between the ground and an aircraft. The figure 1030 megacycles appears as a text overlay. A secondary signal marked 1090 megacycles follows, from air to ground (2:05). A radio tower stands behind a chain link fence with barbed wire (3:00). An interrogator, transmitter, and receiver array. “Deep routing equipment” (3:11). Common and non-common decoders are pointed out in a rack-mounted console (3:41). The camera tilts up to reveal the rest of the radio tower, with a rotating radar dish and a bar-shaped antennae (3:51). Air traffic controllers viewed from behind. A man smokes a cigarette behind the master control box. The associated sector remote control boxes and radar displays (4:28). A pilot’s POV inside an airplane cockpit shows the airborne radar components (4:55). A transponder antenna labeled “do not paint” (5:13). Animation: As a radar pulse flashes, rectangles representing transponders appear, with arrows measuring the distance between them to illustrate modes (5:19). A pulse spacing of 8 microseconds is labeled “Mode A.” A spacing of 17 microseconds, “Mode B.” 21μs = “Mode C” for Pressure Altitude. 25μs = “Mode D,” unassigned (5:55). The Mode A illustration reappears with the words, “64 codes.” A line of pulses appears below with the word “framing” on either side. The pulses are labeled A1, A2, A4, B1, B2, B4 (6:48). Text: “4096 Codes” and “Mode A,B,C,D” (7:31). Code 4031 is spelled out by the pulses (8:06) “Special Position Identification, S.P.I.” (8:12). Air traffic controllers in profile (8:18). The pilot’s radar instrument panel in closeup. Another blip is circled on the radar monitor (8:23). “Code 77: Emergency” and its corresponding radar readout (8:55). “Code 76: Radio Failure” and radar display (9:18). “Code 00: General Purpose” (9:26). A CRT television screen shows the radar display in a wider view. Zoom in (9:43). A radar scan reveals a single blip (10:13). Many cluttered blips depict interference “fruit” (10:34). Reduced clutter post-decoding and de-fruiting (11:03). Raw transponder return codes (11:19). The hand circles an instance of interference, false targets, and jamming (12:29). A man in a tie repositions a model airplane suspended by a string. He indicates the location of the transponder on the bottom of the aircraft (13:14). Heavy circles appear on the radar monitor as rings around the antennae (14:05). The man draws a line to and from the airplane on a chalkboard (14:54). A chalkboard shows an example display in relation to ground distance, “slant range,” and “altitude” (16:00). Additional blips are circled (17:40). A Pan American 707 jet airliner — tail # N707PA, identifying it as one of the first 707’s in the Pan Am fleet — banks away from the camera in aerial photography (18:40). A controller speaks into his radio. A pilot adjusts transponder controls in the cockpit (19:04). A hand points out the result on radar (20:11). Animation: A climbing aircraft and a descending aircraft. A chart depicting different codes for different altitude aircrafts (20:33). A jet flies overhead, past a rotating radar dish (21:54). End title card with ICAO logo (22:47).

This film is part of the Periscope Film LLC archive, one of the largest historic military, transportation, and aviation stock footage collections in the USA. Entirely film backed, this material is available for licensing in 24p HD, 2k and 4k. For more information visit http://www.PeriscopeFilm.com