Avionics News April 2016 - 19

and more challenging training environments," that CFI told
The three air-data instruments worked wholly off air pressure
one successful student. "I don't want their first instrument
and transient pressure differentials.
conditions to be after they're awarded their instrument rating.
Lose the air pump, lose the AI and DG - but keep the turn inIt takes flying in actual IMC to make an instrument pilot."
dicator/coordinator. Conversely, lose electricity, keep the AI and
The successful student also endured a higher-than-typical
DG but lose the electrically driven turn indicator/coordinator.
amount of partial-panel training, also part of the CFI's phiSplit power for split-power source gyros equaled redundancy
losophy.
but at the challenge of flying partial panel.
Together, the challenges of actual
Today, partial-panel training for
IMC and the difficulty of partial-panel
failures in more sophisticated panels
flying helped many students recognize
still highlights the value of standby
the value of standby power to help
power and instruments for modern
TOGETHER, THE
stave off a major contributor to partialelectronic, electrically powered digital
CHALLENGES OF ACTUAL
panel situations. That pilot became a
panels.
IMC
AND
THE
DIFFICULTY
standby-system believer after flying
Failure modes are more varied than
OF PARTIAL-PANEL
partial panel after a vacuum-pump
the old "it's working/it's not working"
failure in IMC - while training with
simplicity of the analog spinningFLYING HELPED MANY
his CFI. A few weeks later, as bad
mass gyros.
STUDENTS RECOGNIZE
luck and old airplane systems would
Redundant instruments are
THE VALUE OF STANDBY
have it, he suffered a generator failure.
required for instrument flight behind
POWER TO HELP
Also in IMC.
all-electronic panels. Standby power,
Alternate power sources for air and
however, is still optional - at least,
electric instruments became a priority
beyond the standby capabilities of the
for that pilot.
main-ship battery.
Today, while many pilots continue
And for many pilots, flying analog
to struggle with partial panel, more
or digital, adding depth and redundanrecognize and are drawn to some of
cy to the sources of gyro power offers
the multiple options that exist for
the best protection against facing a
standby sources of air - and electrical
partial-panel situation when flying
- power for their flight instruments.
inside the eggshell.
Other operators are taking the opportunity to replace old air-driven instruments with elecAnalog redundancy solutions
tronically powered alternatives that fit into the same panel
The aircraft needs two standby or backup power solutions
openings and retire air-driven systems in favor of electrically
to provide full redundancy for the split-power analog panel.
driven versions.
And no question, analog panels will remain a preference for
Of course, still others are opting for the complete digital
many pilots.
makeover.
Some feel no need for the bells and whistles of modern
Regardless of the solution, analog, digital or a blend, standglass cockpits; they prefer the simplicity of six stand-alone
by power for the panel makes sense from many perspectives.
instruments in the panel and the clarity of their failure modes.
If working, fine; if not, no major extrapolation or interpretaThe original standard six pack
tion required. Cover it up with a sticky note and proceed with
For decades, the typical aircraft instrument panel delivered
partial-panel flight.
its redundancy within the three flight gyros of the standard six
Two power failure modes exist with multiple options availpack. That redundancy came in the form of splitting power
able to back up both.
sources among the all-analog flight gyros - an air pump driving
Suction pumps, the dominant air-power source in most
the attitude indicator and directional gyro (or gyro-compass);
and electricity powered the turn coordinator (or turn indicator).
Continued on following page

STAVE OFF A MAJOR
CONTRIBUTOR TO
PARTIAL-PANEL
SITUATIONS.

avionics news

april

2016

Table of Contents for the Digital Edition of Avionics News April 2016