No.
2
FCC:
License Requirement
Certification: Safety Assessment
Audio: Intercom Whine
Audio: Mike, Intermittent Cable
FCC:
License
Requirement
Q
"What is the requirement for an FCC
license in avionics?"
A.
The FCC (Federal Communications
Commission) has no jurisdiction over avionics
shops, but does regulate equipment which radiates
a signal. Thus, transmitters in
aviation are subject to FCC rules.
Such transmitters are found in two-way
radios aboard aircraft (VHF, UHF, HF, SATCOM and
datalink, for example), as well
as transmitters in weather radar,
transponders and DME. The main concern of the FCC
is that repairs to transmitting equipment should
not result in harmonic radiation, spurious
emission and other potential interference to other
radio services.
It is common practice in the avionics
industry for at least one person in a shop
to hold a license, now known as "FCC
General Radiotelephone Operator License".
Other technicians within the shop may perform
repairs under the immediate supervision of the
license-holder.
The FCC license has become
increasingly important for other
reasons. Because there is no avionics
technician license in the U.S., many shops require
an FCC license of a prospective employee as
evidence of basic electronic knowledge. This is
especially true in airline hiring. Many
carriers also require their A&P mechanics to
upgrade skills with an FCC license because so many
aircraft systems. once driven by hydraulics and
pneumatics, are becoming heavily electronic.
Although an avionics technician
license will eventually be required by the FAA,
the FCC requirement should still persist.
The two government agencies are independent of
each other and the FCC will continue to have
jurisdiction over installation and repair of
transmitting equipment.
To take an FCC license exam, a person
must be a legal resident, eligible for employment
in the U.S. This includes all U.S. citizens,
U.S. nationals and citizens of U.S. trust
territories. There are no educational,
training, or experience requirements for taking
the test.
There are 100 multiple choice
quesitons on the test, and a passing grade is 75%.
Once the license is acquired, it is good for life
and does not require renewal.
For
information on a complete home-study course for
preparing for the FCC
exam, click
FCC License
Course
Certification
Safety
Assessment
Q.
"As a manufacturer when am I required to make
a safety assessment of equipment?"
A.
Certain
systems, mainly found aboard heavy transport
aircraft, do require a safety assessment
under FAA Part 25.1309. Typical
systems which require analysis include flight
controls, instruments, displays, and warnings.
Failures in these systems would cause one of the
following levels of criticality:
Minor: Safety is not
significantly reduced and there is a slight
increase in crew workload.
Major: A significant
reduction in safety and aircraft capability,
increase crew workload and possible
injury to crew or passengers.
Hazardous/Severe-Major:
Large reduction in safety margin, physical
distress thatJust
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potentially fatal injuries.
Catastrophic: Failure
conditions which would prevent continued
safe flight and landing.
These consequences are assessed according to their
probability, accomplished at three levels:
Probable
- Failure conditions with a probability of greater
than 1 X 10-5
Improbable
Failure - A probability of 1 X 10-5
or
less, but greater than 1 X 10--9
Extremely
Improbable - A probability of 1 X 10-9
or less.
More
details can be found in FAA AC 25.1309-1A.
For a publication which explains how to perform
the various analyses, click: Safety
Certification
Audio
Intercom
Whine
Q.
"I hear a musical tone in my headsets.
What could be the problem?"
A.
Typically
caused by the alternator. it can be verified
by changing engine RPM; the pitch of the whining
sound rises and falls with speed of the engine.
The source is usually worn or dirty slip rings,
which spark and radiate interference. In some
cases, the sound grows louder if you switch on
more equipment, and draw more amperage from the
alternator.
If the sound is rough and
raspy (not pure), there could be a defective diode
in the alternator, preventing full rectification
into DC.
If cleaning, repairing or replacing the
alternator does not reduce the noise
sufficiently, consider adding a filtering device
as close to the alternator as
possible. These are available as
bypass capacitors, which shunt the interference to
ground, or inductive chokes which help prevent the
energy from backing up into the aircraft's primary
power cables.
Audio
Microphone,
Intermittent, Cable
Q.
"I get reports that words are cutting
out when I transmit. What could be the
problem?"
A.
The
most abused part of the microphone is where its
cable enters the microphone case or where the
cable joins the plug. Each time you lift the mike
from its mounting clip, the cable flexes at these
points and, in time, metal fatigue breaks a wire.
You can often determine this by listening in your
headphone and talking, while grasping the cable at
each of those weak points and moving it in a
circle. This usually causes intermittent
audio as the broken wire makes and breaks
and isolates the problem. Because mike
cables are often within molded fittings or consist
of extremely fine tinsel conductors, it is prudent
to replace the complete cable assembly. 
Note
that many mikes have a three-wire circuit;
audio, keying and ground. The problem mentioned
above relates only to a break in the audio
lead. You would still transmit a
"carrier" because the key lead could be
functioning. If you get reports of both
intermittent audio and carrier
simultaneously, this suggests a broken
connection in the keying lead, which is operated
by the push-to-talk switch. Again, you might
try moving the wire around where it enters either
the mike jack or mike case to localize the break
