1.0 Introduction
The F/A-22's avionics and software system is the most advanced
ever integrated into an aircraft. It is the first aircraft
to use integrated avionics, where the weapons management
system, electronic warfare system and the AN/APG-77 radar
work as one, giving the pilot unprecedented situation
awareness.
A joint venture of Northrop Grumman's Electronic Sensors
and Systems Division (ESSD) and Raytheon is developing
the advanced AN/APG-77 active-element electronically scanned
array radar for the F/A-22.
2.0 Capabilities
The AN/APG-77 radar is designed for air-superiority and
strike operations and features a low observable, active
aperture, electronically-scanned array with multi-target,
all-weather capability.
The radar is key to
the F/A-22's integrated avionics and sensor capabilities.
It will provide pilots with detailed information
about multiple threats before the adversary's radar
ever detects
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the F/A-22. This is also called BVR, or Beyond Visual
Range capability.
It will give an F/A-22 pilot the possibility in air-to-air
combat, to track, target and shoot at multiple threat
aircraft before the adversary's radar ever detects the
F/A-22.
3.0 Technology
The F/A-22's AN/APG-77 radar is an active-element, electronically
scanned (that is, it does not move) array of around 2000
finger-sized transmitter / receiver modules. Each module
weights ca 15g and has a poweroutput of over 4W. The APG-77
is capable of changing the direction, power and shape
of the radar beam very rapidly, so it can acquire target
data, and in the meantime minimizing the chance that the
radar signal is detected or tracked.
Most of the mechanical parts common to other radars have
been eliminated, thus making the radar more reliable.This
type of antenna, which is integrated both physically and
electromagnetically with the airframe, provides the frequency
agility, low radar cross-section, and wide bandwidth necessary
to support the F/A-22's air dominance mission.
One requirement that drove all of the ATF designs
was a wide field of regard for sensors, enabling the Raptor
to acquire and track multiple targets beyond visual range.
The requirement called for a 120-degree radar field of
regard on each side of the nose.
A forward-looking infrared search and track capability
was also desired. Lockheed approached the field-of-regard
requirement for the radar with three radar arrays placed
in the nose of the aircraft (one facing forward and two
facing sideways). Each wing root carried an infrared search
and track system that operated through faceted windows.
4.0 Radar Software
The avionics software is to be integrated in three blocks,
each building on the capability of the previous block.
Block 1 is primarily radar capability, but Block 1 does
contain more than 50 percent of the avionics suite's full
functionality source lines of code (SLOC) and provides
end-to-end capability for the sensor-to-pilot data flow
This Block 1 software enables the basic operation of the
radar and its initial mode complement, including the simultaneous
operation of search and track modes and systems health
and maintenance or built-in-test modes. For more information
on the F/A-22 software in general, click
here.
At the Boeing Avionics Integration Laboratory the
F/A-22 radar was integrated with the avionics mission software
and other aircraft avionics sensors such as the electronic
warfare system, and the communications, navigation and
information systems.
5.0 Testing
By the first quarter of 1998, the radar was delivered
to The Boeing Company's F/A-22 Avionics Integration Laboratory
in Seattle, Wash., where engineers integrated the radar
with other F/A-22 avionics.
Meanwhile, flight testing of a second F/A-22 radar
continued aboard a modified Boeing 757 testbed aircraft
at ESSD. The test bed consistsed of an F/A-22 forward fuselage
installed on the 757's forward pressure bulkhead. Electronic
warfare (EW) and communication, navigation and identification
(CNI) sensors were mounted directly on the sensor wing,
which was designed to simulate the sensor positioning
found on the F/A-22's wings.
The cabin had space for 30 software engineers and technicians
who could evaluate avionics and identify anomalies, in
real time. A simulated F/A-22 cockpit was installed in the
cabin of the Flying Test Bed. It had all primary and secondary
F/A-22 displays, as well as the throttle and stick.
The conducted flight tests successfully demonstrated the
expected levels of performance of the F/A-22 radar, including
basic search and track functions.
Full-scale production of the F/A-22 radar is scheduled to
begin in 1999.
Source: Lockheed,
Boeing, Raytheon, Texas Instruments, USAF
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