An overall check of a computer can be done by
the use of a maintenance program. The maintenance
program provides a thorough and rapid method for the
detection of failures in a specific portion of the
computer. This type of overall maintenance check is
flexible and efficient. The programs may use the
same type of tape, memory, computing, and external
storage media as operational programs. The
maintenance program can be altered when the
computer or auxiliary components are changed. The
program can also be constantly improved. Generally,
no extra test equipment is required since the computer
circuits are used to perform the test. Testing by means
of maintenance programs results in the computer
circuits being used in a more comprehensive manner
than during normal program execution. When a
program has been checked and accepted as a good
maintenance tool, it is not subject to deterioration. In
contrast, test equipment may be checked and accepted
only to become unreliable shortly after being placed
Maintenance programs are divided into two main
reliability and diagnostic. Maintenance
programs that are used to detect the existence of
errors are called reliability programs. Reliability
programs should be arranged to check as many
computer circuits as possible.
Maintenance programs that are used to locate the
circuits in which computer malfunctions originate are
called diagnostic programs. An effective diagnostic
program should locate the source of trouble as closely
as possible. Actually, in many cases, reliability
programs have some diagnostic features, just as
diagnostic programs have some reliability features.
For convenience, a program is called either a
reliability or diagnostic program, depending on its
intended emphasis. In general, programs that check
rather than diagnose are shorter and simpler.
PERIPHERAL AVIONICS SYSTEMS
Learning Objective: Identify peripheral
avionics systems and describe their
interaction with the computer.
The aircraft computer is considered the most
important avionics system in achieving the mission of
the aircraft. However, the success of the computer
depends upon its external sensors or other avionics
systems. The quality of data fed to the computer
determines the quality of data fed out of the computer.
The following avionics systems provide inputs to and
receive outputs from the computer: navigation, radar,
ordnance/weapons, and data link. These are only a
few of the major aircraft avionics systems that
interface with the airborne computer.
Navigation systems are designed to tell pilots
where they are, where they have been, and where they
are going. The TACAN/DME system provides
known station reference points, while an inertial
navigation system provides continuous updating of
such information as latitude and longitude. This
information is fed to the computer where it is
compared, updated, and sent out to other systems.
A search radar system is designed to give visual
indications of what is around the aircraft. Some of the
present-day aircraft have a 150-mile or greater range.
Depending upon the size and/or speed of the radar
indications, a computer can determine whether the
target is stationary or moving, a land mass or an
aircraft, friendly or unfriendly, and many other items
of information. If a target is determined to be
unfriendly, a tracking radar can be used to tell the
pilot what to do to eliminate the target.
The design characteristics and ballistics of the
many types of ordnance, weapons, and missiles
require the use of a computer to store the information.
The airborne computer aids the pilot by telling
him/her when to release the weapons. The computer
greatly increases the pilots chances of destroying
Combat aircraft have to have the most up-to-date
information available to successfully complete
combat missions. On an aircraft carrier, the combat
information center, CIC, is normally in constant
contact with an airborne CIC. The airborne CIC is
usually an E-2 or P-3 aircraft. These two CICs will
crosstalk by use of the data link system. Basically,
data link involves a series of transmitted pulses that
represent information. The pulsed information is sent
to the computers of all combat aircraft to enhance
their chances of success.