February 21, 1964 Electronics
[Table of Contents]
Wax nostalgic about and learn from the history of early electronics.
See articles from Electronics,
published 1930 - 1988. All copyrights hereby acknowledged.
this 1964 article in Electronics magazine, the U.S. Air Force's decision to
build radar systems that would enable low altitude, terrain-following flight paths for
strategic and tactical aircraft was in response to the shooting down of (Francis)
U-2 spy craft in 1960. The event made clear that simply flying high over enemy territory
and dropping bombs would not be a reliable strategy since surface-to-air missiles could
reach and destroy aircraft before they got to their targets. Terrain-following capability
on the part of bombers and fighters would add a major element of surprise since approach
paths could be masked until it was too late to take offensive action. That approach was
not without its risks and faults, as made apparent by the
movie satire that poked fun at the very concept. In the 1964 (same year) hit film as you might recall,
B-52 pilot Major T. J. "King" Kong (Slim Pickens) had
been ordered to drop nukes on a base inside the U.S.S.R. His bomber ended up needing to
navigate through mountains and valleys en route - a feat probably not possible under
manual control. Of course the most famous scene in the movie is Major Kong "yee-hawing"
and waving his cowboy hat as he rides the bomb down.
Attack Planes Hug Hostile Terrain with New Radar
Advanced capability radar displays the terrain in front of the 650-mph
B-52H, enables safe hedge-hopping on bomb runs. Planes operate much below 1,000 feet.
To evade enemy radar, all three services now want terrain-following radar
By John F. Mason
Senior Associate Editor
Harold C. Hood
Regional Editor, Los Angeles
Proof of Soviet ability to knock down high-flying planes (the U-2) forced the U. S.
to beef up capability for low-level penetration that would avoid detection by enemy radar.
New military planes are being developed to fly ground-hugging missions, and some existing
high-altitude aircraft are being retro-fitted to drop down to "tree top" level for the
last leg of their approach.
Increased emphasis on this low-altitude strategy is creating greater need for precise
instrumentation that enables an aircraft or drone to maintain a desired altitude above
the ground and avoid obstructions, regardless of visibility.
Terrain-following radar (TFR), to carry out these missions, is being developed for
all three military services. Air Force, which more or less led the search for new techniques,
has TFR in the B-52H bomber, and the F-105 fighter. Equipment is being developed for
the TFX long-range tactical fighter now being built, and will be developed for any low-altitude
penetrator built in the future.
Navy has a number of carrier-based planes capable of low-altitude operations. Those
known to have flown with TFR are the A5 Vigilante, the A2F Intruder and the A4D. Navy
says the gear is still in R&D.
Displays for automatic TFR, built by Autonetics, consists of (center)
plan position indication (PPI) and 3-D terrain to give azimuth, range and elevation information.
Upper scope tells position of aircraft (circle) in relation to where automatic terrain
following command (dot) says it should be.
Compact terrain-following radar in pod attached here to Navy's A4C
Skyhawk has also been tested by USAF.
Army has an active program going for the Mohawk surveillance plane and a healthy interest
in the complicated problem of getting TFR for helicopters.
Cornell Aeronautical Laboratory (CAL) has been an important research and development
arm of the military on TFR for 10 years.
CAL's Autoflite system was designed, fabricated and flight tested under sponsorship
of USAF's Aeronautical Systems Division. Industry has been active in the field for the
past four or five years and will be more active in the future.
Equipment - Terrain following refers to vertical change in flight
direction - going up or down to maintain a constant altitude above the ground. Terrain
avoidance implies ability to turn left or right to avoid obstructions or to take advantage
of the hills that protect a valley. The more sophisticated units provide both. Equipment
may be manual, automatic, or both. Other functions sometimes connected with TFR are air-to-air
search and ground mapping.
Texas Instruments - Active in the field for several years, TI is
known to be working on three important TFR projects: $5-million subcontract from McDonnell
for development work on a low-altitude TFR system for the RF4C - USAF's reconnaissance
model of McDonnell's Phantom II fighter; subcontract with General Dynamics for equipment
for the F-111 (TFX); and a contract with the Army Electronics Command for an advanced
system for Army's Mohawk surveillance aircraft.
Autonetics-North American's Autonetic's division has produced TFR for the F-105F Thunderchiefs,
the German Air Force F104G Starfighters, and - with IBM and AC Spark Plug-equipment for
The firm is developing a series of terrain-oriented radars for possible use on a number
of future military aircraft. For the VAX program to develop a triservice attack aircraft,
a multi-mode radar with automatic terrain-following capability is proposed. Beyond VAX,
Autonetics is working on the XR-45, a system that will use thin-film microcircuits and
stress reliability. Meantime-before-failure (mtbf) goal for the entire multimode radar
system is from 300 to 500 hours; mtbf for the automatic terrain-following mode will be
from 2,000 to 4,000 hours.
Autonetics's emphasis on solid-state components is shifting to microminiature techniques.
Except for the transmitter and power supply the whole system is microminiaturized. Thin-film
is used for the high frequencies. Integrated circuits are as yet of little use anywhere
in the system because of the high frequencies used.
NASARR System - The firm has recently demonstrated their modified R-14 NASARR (North
American Search and Ranging Radar), described as the first system with simultaneous automatic
terrain-following, manual terrain-following and manual terrain-avoidance capabilities.
The radar uses a data processor with solid-state electronic circuits.
The automatic terrain-following mode guides the plane at a prescribed altitude while
manual terrain avoidance gives the pilot a broad radar view of the terrain ahead, permitting
selection of flight-path alternatives. Automatic terrain-following signals are provided
by an altimeter in level areas, and by the forward-looking radar over hills or mountains.
The radar has four displays - plan position indication (PPI), three-dimensional terrain,
elevation-angle, and manual terrain following.
The PPI and 3-D displays are combined on one tube, giving azimuth and range position
in relation to mountains. As a mountain comes into range. it appears on the azimuth-angle
scope. With the aid of the manual terrain-following display, the pilot is able to verify
automatic terrain following or fly manually over the mountain.
General Dynamics/Electronics - GD/E built the radar portion of the
navigation system for Navy's A5 (A3J) Vigilante. The radar is part of the REINS (radar-equipped
inertial navigation system) built by Autonetics. The system is used for both low and
high-level penetration, and for launching air-to-ground missiles.
Antenna dish permits 90-deg azimuth scan and wide elevation coverage
in automatic TFR unit built by Autonetics.
GD/E has checked out a compact TFR unit on a B-25 for more than 150 hours at 400 feet,
and on a B-26 for more than 50 hours. The basic system consists of an on-bore-sight radar
with a non-scanning antenna 8.3 inches in diameter, and a built-in electronic analog
computer. A pilot display and automatic pitch control signals are provided.
The radar is housed in a pod the size of a standard 250-pound bomb, mounted under
the wing or in the nose of an aircraft or drone. It weighs 40 pounds, occupies 1/2 cubic
The Ku-band radar detects small individual objects within a continually
moving field a tenth of a mile deep at a selected distance ahead. Terrain information
from the antenna is fed to the small analog computer where it is correlated with flight
characteristics and altimeter input. Continuous flight instructions are presented to
the pilot through a simple meter or to the automatic pilot. No radar scope presentation
is required. Instrumentation may be simplified further by combining a climb-and-descend
indicator with the attitude indicator.
For safety, an r-f signal is continually fed into the waveguide feed and then through
the system. If a failure occurs while the pilot is flying manually, a warning light turns
on. Failure during automatic flight results in an automatic climb command to the autopilot.
GD/E's system was developed with company funds, It differs from most other systems
in that it uses a fixed beam rather than vertical scanning. It also depends more heavily
on input from an altimeter than do other systems. The fixed beam is directed with a fixed
depression angle. It is stabilized by servoing it to the angle-of-attack data.
Other Producers - Under an "integrated approach," Hughes is incorporating
air-to-air search and ground mapping along with TFR. Hughes has been under contract to
improve a prototype system built at the Navy Avionic Facility in Indianapolis (NAFI).
The Naval Ordinance Test Facility, China Lake, Calif. is also working on TFR. Other firms
include Raytheon, Emerson Electric and Norden.
Posted January 11, 2019