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Aerospace Careers: Avionics Communications Systems
Communications systems are a necessary part of NASA's aeronautical operations at the Dryden Flight
Research Center. Research flights cannot take place without air-to-air and air-to-ground communications.
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| Aircrew use intercommunications systems. |
Research pilots must be in constant radio contact with pilots in nearby "chase" aircraft, who serve as an
extra pair of eyes for added safety while observing test events on the research aircraft. Equally important is the
need for research pilots to be in continuous radio contact with engineers and researchers who monitor flights
in control rooms on the ground. Pilots must also talk with people in airfield control towers and with air
traffic controllers who help make flying as safe as possible.
There are two basic types of avionics communications systems used in NASA aircraft.
Radio communications systems allow a pilot or crewmember to speak with people
in another aircraft (air-to-air) or with someone at a ground station (air-to-ground).
The intercommunications system (ICS) allows a pilot or crewmember to communicate
with another person in the same aircraft.
Avionics communications systems at Dryden are maintained and modified by electronics technicians of
the Communications, Navigation, and Video Group of the Avionics Branch. This group is also the source
for engineering and technical support when new radio systems need
to be designed and installed in the Dryden aircraft fleet, and when aircraft modifications are planned that
affect an aircraft's
communications system.
Aircraft Communications Systems
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| SR-71 aircraft |
There are three types of aircraft radios used at Dryden. They are HF (high
frequency), VHF (very high frequency), and UHF (ultra high frequency). Each
radio is a combined transmitter-receiver (transceiver) used for air-to-air
and air-to-ground communications.
High Frequency radios are used by Dryden pilots when it is necessary to communicate one thousand miles
or
more. HF radios can be installed in any aircraft when necessary. At Dryden they are used routinely in the
SR-71s. The ability to communicate over distances of several thousand miles was a necessary feature for their
high-flying aerial reconnaissance role during Air Force service. This same HF capability is used by NASA when
the aircraft, cruising at three times the speed of sound (2100 mph), flies research missions over the entire
western portion of the nation in less than 75 minutes.
VHF radios allow Dryden pilots to communicate with military and general aviation aircraft, and airport
and facility personnel within an aircraft's line-of-sight. This capability is needed when an aircraft is flown
across country to another NASA or a military installation, a civilian airfield, or is diverted to a civilian airfield
because of cross-country weather conditions.
UHF radios are the "bread and butter" units used by NASA. Dryden pilots use UHF units to communicate
with "chase" aircraft, control rooms monitoring a research mission, other government radio stations taking part in
a research project, and all military control towers and air traffic control facilities. Dryden pilots flying to
other military bases use UHF radios to communicate with those facilities on the way and during taxi, takeoff,
and landing operations. Like VHF, UHF radios are also limited to line-of-sight communcations.
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| Radios (left to right) ARC-164, ARC-164 UHF, ARC 182 UHF/VHF,
ARC 195. |
All of Dryden's F-15, F-16, F-18, and SR-71 research aircraft carry UHF and
VHF radios. This gives each aircraft the necessary communications capability
regardless of where a research mission takes them.
A functioning UHF or VHF radio is required for all aircraft flying research
missions, regardless of where they are flown. This includes support (chase)
aircraft.
Most radios used at Dryden are made for military aircraft. They are designed and developed to operate
in extreme flight environments where temperatures and air pressures can be very high and very low.
As radios are developed and upgraded for the military services, the newer models
are also obtained by NASA and installed in Dryden aircraft by the Communications
Section. Among the new radios expected in the future are units with combined
UHF, VHF, and global positioning satellite (GPS) functions.
Mobile Communications Systems
The Communications, Navigation, and Video Group is also responsible for the design, fabrication,
installation and maintenance of avionics and mobile communications systems used in ground support vehicles at Dryden. These vehicles are used by aircraft maintenance,
project, and engineering personnel to communicate with mission control rooms, pilots, and other aircrew
members during pre-flight and post-flight activities on the flightline, during research flights, and while the aircraft
is being taxied to and from
the runway.
Research projects occasionally require project personnel to be at remote ground sites away from Dryden
to monitor recording equipment and instrumentation during certain portions of a flight. The ground support
vehicles, with their air-to-ground communications systems, are used as on-site command and control
centers during these remote-area activities. An example of how they are currently used at a remote site is the
collection of air pressure data from sonic booms on instruments placed at several widely separated sites on the ground.
To obtain accurate data, engineers had to communicate with pilots as they flew high above them at
supersonic speeds.
Ground support vehicles also provide the vital communications links with Dryden officials and other
agencies during an off-site emergency such as an aircraft accident.
One of the most unique communications systems engineered and created at
Dryden is the combined aircraft-mobile-portable communications system used
in the Space Shuttle Convoy Command Vehicle. This vehicle is used by the
NASA convoy commander and other shuttle personnel during shuttle landings
at Edwards. The convoy command vehicle is a converted motor home with an
intercommunications system and a radio network that gives the NASA convoy
commander voice
communications with the shuttle crew, mission control, and ground support
vehicles during the entire landing recovery sequence. Over this communications
network, the convoy commander and other personnel inside the convoy command
vehicle coordinate all of the post-flight orbiter inspection and maintenance
activities, egress of the shuttle crew, and off-loading of time-critical
science experiments.
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| Convoy command vehicle. |
Maintenance
Most aircraft communications units are rugged and very reliable. They contain highly complex circuitry
and generally require little maintenance.
It usually takes just a few minutes to remove a radio from an aircraft and return it to the radio shop where it
can be analyzed for a malfunction.
One of the most important pieces of equipment used to troubleshoot, test, repair,
align, and adjust radios is a Communications Analyzer, which can be compared
to a computerized tune-up unit in an automotive shop. This unit can check many
radio functions within minutes, saving considerable time and expense. multimeters,
oscilloscopes, power meters, and watt meters. Many manufacturers build special
test sets for specific radios and these test sets are among the many pieces
of equipment normally found in a radio shop.
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| F-18 radio removal. |
Experience
Individuals interested in working in the NASA aircraft communications field must have a broad background
in aviation electronics (avionics) and in mathematics. Knowledge of aircraft structures and general shop
experience would also be useful for applicants. Possessing an FCC General Radiotelephone Operators
License is also helpful.
Most community colleges offer formal training in electronics, while most technical schools have courses
specifically covering aviation electronics.
Formal schooling and on-the-job training in the avionics communications field
is also available from the military services. On-the-job experience can also
be found at commercial avionics facilities on or near most airports.
Document Number: IS-97/08-DFRC-02
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