F-111 Terrain Following Radar ~ 1967 US Air Force Training Film TF-6851 (Patreon)

more at http://quickfound.net/

Originally a public domain film from the US Air Force, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.

The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).

https://en.wikipedia.org/wiki/Terrain-following_radar

Wikipedia license: http://creativecommons.org/licenses/by-sa/3.0/

Terrain-following radar (TFR) is a military aerospace technology that allows a very-low-flying aircraft to automatically maintain a relatively constant altitude above ground level and therefore make detection by enemy radar more difficult. It is sometimes referred-to as ground hugging or terrain hugging flight. The term nap-of-the-earth flight may also apply but is more commonly used in relation to low-flying military helicopters, which typically do not use terrain-following radar. The technology was originally developed by Ferranti for use with the TSR-2 aircraft...

The system works by transmitting a radar signal towards the ground area in front of the aircraft. The radar returns can then be processed to see how the terrain ahead varies, and then used by the aircraft's flight computers to calculate flight-path changes in order to maintain a reasonably constant height above the earth. The computer will consider many factors in determining the flight path for the aircraft, such as distance to the forward terrain, aircraft speed and velocity, angle of attack and quality of signal being returned.

Strike Aircraft Use

Advantages and Disadvantages

Terrain following radar is primarily used by military strike aircraft, to enable flight at very low altitudes (sometimes below 100 feet/30 metres) and high speeds. Since radar detection by enemy radars and interception by anti-aircraft systems require a line of sight to the target, flying low to the ground and at high speed reduces the time that an aircraft is vulnerable to detection to a minimum by hiding the aircraft behind terrain as far as possible. This is known as terrain masking.

However, radar emissions can be detected by enemy anti-aircraft systems with relative ease once there is no covering terrain, allowing the aircraft to be targeted. The use of terrain-following radar is therefore a compromise between the increased survivability due to terrain masking and the ease with which the aircraft can be targeted if it is seen.

Even an automated system has limitations, and all aircraft with terrain-following radars have limits on how low and fast they can fly. Factors such as system response-time, aircraft g-limits and the weather can all limit an aircraft. Since the radar cannot tell what is beyond any immediate terrain, the flight path may also suffer from "ballooning" over sharp terrain ridges, where the altitude becomes unnecessarily high. Furthermore, obstacles such as radio antennas and electricity pylons may be detected late by the radar and present collision hazards...

https://en.wikipedia.org/wiki/General_Dynamics_F-111_Aardvark

The General Dynamics F-111 Aardvark is a retired American supersonic, medium-range interdictor and tactical attack aircraft that also filled the roles of strategic nuclear bomber, aerial reconnaissance, and electronic-warfare aircraft in its various versions. The word "aardvark" is Afrikaan for "earthpig" and reflects the look of the long nose of the aircraft that might remind one of the nose of the aardvark. Developed in the 1960s by General Dynamics, it entered service in 1967 with the United States Air Force. The Royal Australian Air Force (RAAF) also ordered the type and began operating F-111Cs in 1973.

The F-111 pioneered several technologies for production aircraft, including variable-sweep wings, afterburning turbofan engines, and automated terrain-following radar for low-level, high-speed flight. Its design influenced later variable-sweep wing aircraft, and some of its advanced features have since become commonplace. The F-111 suffered a variety of problems during initial development. Several of its intended roles, such as an aircraft carrier-based naval interceptor with the F-111B, failed to materialize.

USAF F-111s were retired during the 1990s with the F-111Fs in 1996 and EF-111s in 1998. The F-111 was replaced in USAF service by the F-15E Strike Eagle for medium-range precision strike missions, while the supersonic bomber role has been assumed by the B-1B Lancer. The RAAF was the last operator of the F-111, with its aircraft serving until December 2010...