Information supplied and copyrighted
by Joe Baugher
Electronics of F-16
Fighting Falcon
Last revised March 19,
2000
The primary target detection sensor of
the F-16A/B is the Westinghouse AN/APG-66 pulsed-Doppler radar. Pulse-Dopper radars
operate by measuring the frequency shift that is created by target velocity in order to
discriminate between a genuine aircraft and ground clutter. The APG-66 has a medium pulse
repetition frequency or PRF for short (typically 10 to 15 kHz). It operates in the I/J
band and has a flat-plate planar array antenna. Sixteen operating frequencies are
available within the I/J band, and the pilot can select between any four of them.
The APG-66 reduces the radar data to
digital form and presents the pilot with a synthetically-generated image made up of a set
of predefined symbols. The display is free from clutter and is much easier to read than
previous displays, but the ability to discriminate between real and false targets depends
entirely on the quality of the software used to control the signal processing equipment.
Radar operating modes may be selected by
the pilot by using either the throttle, the sidestick controller, or knobs on the radar
control panel. The primary air-to-air search mode is Downlook, which provides clutter-free
indication of low- flying targets. Fighter-sized aircraft can be detected at ranges of up
to 35 miles. In the Uplook mode, there is no need for the filtering out of spurious
responses from the ground, and the pilot can detect targets at ranges of up to 50 miles.
Four modes are available for air-to-air
combat. In the Dogfight mode, the radar automatically scans a 20-degree by 20-degree field
in the forward direction. If the pilot can see the the target in his HUD, and the range is
less than ten miles, the radar will automatically lock on. If high-g maneuvers are to be
carried out, the area to be searched can be altered to a 40-degree by 10-degree pattern.
If multiple targets are present, the pilot can press the Designate button on his sidestick
controller. The radar will then operate in a slim narrow-beam mode, and by maneuvering his
aircraft, the pilot can place the beam onto the required target. When he releases the
designate button, the radar will acquire and track the chosen target. A Slewable
air-combat mode can be used to allow the scan pattern to be moved in anticipation of
target maneuvers.
Seven different modes are available for
air-to-surface attacks. The first of these is Air-to-Ground Ranging, which is
automatically selected during continuously-computed impact point (CCIP) and dive-toss
attacks. CCIP attacks use a ground mapping mode, which gives a plan position indicator
display at 10, 20, 40, or 80 nm range, and scan widths of plus or minus 10, 30 , or 60
degrees. There are dedicated sea-surface search modes, which are designed to eliminate the
clutter caused by spurious reflections from ocean waves. There is a Beacon mode which can
be used in conjunction with ground-located radar beacons to take navigational fixes or to
carry out offset weapons delivery. In the air-to-air role, this mode is used by the radar
to locate flight refuelling tankers by interrogating their beacons. There is a Freeze mode
in which the radar carries out a quick scan, and the image is held on the display while
the radar transmitter is shut off. A moving symbol on the display continues to simulate
aircraft motion. There is a special Doppler beam sharpened mode which is capable of
achieving a higher definition of ground features. This mode relies on the processing of
Doppler shift information, and is available only at angles between 15 degrees and 60
degrees off the aircraft's velocity vector. If the aircraft should happen to bring the
area being viewed to within 15 degrees of the aircraft's centerline, the radar will
automatically switch to the normal ground mapping mode.
Integration of the F-16 avionics makes
extensive use of the MIL-STD-1553 databus.
In 1980, Westinghouse was awarded a
contract to develop a programmable signal processor and a dual mode transmitter for the
APG-66. The dual-mode transmitter would use low PRFs for air-to-ground work, and medium to
high PRFs for air-to-air combat. These modifications were intended to match the
performance to the AMRAAM missile and to improve the air-to-ground capability.
All F-16C and D aircraft carry the
improved Hughes APG-68 radar with new dual-mode traveling wave tube technology to provide
low, medium, and high PRFs. A Programmable Signal Processor (PSP) is fitted which is based
on VHSIC technology. The APG-68 has a longer range and can handle radar-guided missiles at
BVR, including the AIM-120A AMRAAM "fire-and-forget" missile. The improved data
processing capability of the APG-68 enables the set to operate in a track-while-scan mode,
which makes it possible to follow multiple targets at the same time and rank them in order
of priority. Higher-resolution mapping modes are also available. A raid cluster resolution
mode is available with the APG-68 which allows the pilot to distinguish between the
individual aircraft flying in a tight formation at long range. The set also has an ACM
(air combat maneuvering) mode which allows the radar to follow hard-maneuvering targets at
short ranges.
Data from the radar and navigation
systems are displayed to the pilot on either a heads-up or heads-down displays. The HUD is
built by Marconi Avionics (now known as GEC Avionics). Marconi was a pioneer in the
development of HUD technology, and built the first HUD to enter service on a production
aircraft, applied to the Hawker Siddeley Buccaneer in 1960. If the canopy happens to be
shattered by the impact of a particularly large bird, the HUD is robust enough to act as a
temporary windshield to protect the pilot. The field of view of the HUD of the F-16A/B is
15.5 degrees in azimuth and 9 degrees in elevation. In the LANTIRN-equipped later models
of the F-16C or D, the field of view of the HUD is 30 by 20 degrees.
The basic communications installations in
the F-16A and B consists of Collins ARC-186 VHF AM/FM and Magnavox ARC-164 UHF
tranceivers, a Magnavox KY-58 secure voice system, and an interference blanker by
Novatronics.
Between 1984 and 1986, the USAF F-16
force was equipped with the JTIDS jam-resistant command, control, and communication
system.
The basic radar warning system (RWR)
carried by the F-16 is the Itek ALR-69. It was based on the earlier ALR-46. It has five
general purpose surveillance receivers plus a sixth frequency-selective receiver. The USAF
has been reluctant to export the ALR-69 to foreign air forces. The ALR-74 is scheduled to
replace the ALR-69. The F-16C/D Block 50/52 carries the Loral ALR-56M radar warning
receiver.
The F-16 can carry the ALQ-119 or the
more modern Westinghouse ALQ-131 electronic countermeasures pod on the fuselage centerline
point. The Westinghouse ALQ-131 is a 573-pound modular pod-mounted system capable of
coping with a wide range of threats. By selecting individual modules for inclusion in the
pod, the user can configure the pod to handle threats spread over one to five frequency
bands. Modules are available to cope with all frequencies used by current anti-aircraft
missile systems, and both noise and deception-jamming modes are available. The pod has its
own digital computer which can be reprogrammed on the flightline before takeoff to match
the threat to be encountered on the mission.
Sources:
- Combat Aircraft F-16, Doug Richardson,
Crescent, 1992.
- General Dynamics Aircraft and their
Predecessors, John Wegg, Naval Institute Press, 1990.
- The American Fighter, Enzo Angelucci and
Peter Bowers, Orion, 1987.
- United States Military Aircraft Since
1909, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.
- F-16 Fighting Falcon--A Major Review of
the West's Universal Warplane, Robert F. Dorr, World Airpower Journal, Spring 1991.
- The World's Great Interceptor Aircraft,
Gallery, 1989.
- Modern Military Aircraft--F-16 Viper, Lou
Drendel, Squadron/Signal Publications, 1992.
- Lockheed F-16 Variants, Part 1, World
Airpower Journal, Volume 21, Summer 1995.
- E-mail from Ben Marselis
