1 - The Black Vault

PRAETORIAN STARSHIP
any other in the world on TF/TA operations. Educating
USAF operators and maintainers on the
new system proved more challenging. The basic
problem with USAF personnel was that the radar
was classified and that operational information
about it was not readily accessible. Flight
crews and maintainers could not easily refer to
the technical orders, thus hindering their ability
to attain vital systems knowledge. In the flying
squadrons, electronic warfare officers kept radar
manuals in their EW safe and signed them out to
pilots and navigators when requested. Because
they were all classified, the manuals could not be
removed from the squadron building, thus preventing
self-study during off-duty periods. An unclassified
article, published by the McDonnell-
Douglas Aircraft Corporation in 1965, discussed
the AN/APQ-99 TF/TA radar installed in the RF-
4 aircraft. The article was reproduced and dis -
tributed to pilots and navigators while they were
attending initial Talon training at Pope AFB. As
late as 1968, when the 7th SOS received its four
Combat Talons, the RF-4 article was still con -
sidered the best unclassified document available
on the TF/TA system.
Efforts to declassify the radar and to provide
better information to the Combat Talon community
was realized in 1971, when the annual Combat
Talon Management Review Conference adopted
the first unclassified Lockheed Technical Manual
(LTM) that contained detailed information describing
the TF/TA radar system. The description
of radar operations contained in the first LTM
was improved over the years and included in subsequent
LTMs produced for the Combat Talon .
and azimuth, could distinguish between obstacles
located at or above the true horizontal plane of the
aircraft and those located below it. In addition
terrain-following radar (TFR) required a good horizontal
reference for its antenna. Its beam had to accurately
measure the angular aircraft-to-obstacle
relationship in the vertical plane and feed this infor -
mation to a computer, which, in turn, could furnish
necessary climb and dive commands for maintaining
desired vertical-terrain clearances.
The TFR employed either the aircraft’s Doppler
system or its inertial navigation system for its antenna’s
primary vertical and horizontal reference.
For the AN/APQ-122(V)B radar, the stabilization
reference could be manually or automatically
switched to the MD-1 gyros if the LN-15J became
unreliable or inoperative. If the Doppler failed
while utilizing the AN/APQ-115, however, the ra -
dar would display a fail indication, and TF opera -
tion normally would be discontinued. The required
radar beam angular resolution and precision for
terrain following and terrain avoidance was attained
by the monopulse resolution improvement
(MRI) technique (fig. 6).
The AN/APQ-115 radar had a single contoured,
spoiled parabola face antenna for its operation. On
the AN/APQ-122, a special flat-face antenna and a
separate X band receiver were used to generate
the MRI video. During the transmit cycle the radio
frequency energy was first split into two parts that
had an equal amplitude and phase relationship.
Then, the radio frequency energy was radiated
through a grid circular polarizer screen from the
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Terrain-Following Radar System Theory*
To appreciate the low-level adverse-weather ca -
pability of the Combat Talon weapons system, one
must understand the basic operation of the TF/TA
radar. Conventional airborne search radar provided
range and azimuth data of sufficient accuracy
for normal high-level aircraft navigation. The
beams generated by these radar, however, did not
possess the vertical angular resolution necessary to
provide the precision required for terrain-following
and terrain-avoidance flight.
Terrain-avoidance radar required good horizontal
antenna stabilization and a radar-beam
pattern that, besides detecting targets in range
I,,... ;^|_.|
Figure 6. Monopulse Resolution Improvement Technique
(Source: 1st SOW, CTF Student Study Guide, Hurlburt Field,
Fla., 23 June 1991.)
__________
*The following description was extracted from the USAF Combat Talon Formal School publication, AN/APQ-122(V)8 Terrain-Following Radar
Handout, 1 January 1979. Information in this handout was later updated and included in the 1st SOW-Central Training Flight (CTF) Combat
Talon Formal School publication, Student Study Guide, Hurlburt Field, Fla., 23 June 1991. Information regarding the AN/APQ-99 and the
AN/APQ-115 was extracted from the publication titled McDonnell Aircraft Field Support Digest, Fourth Quarter, 1965.
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