Avionics News May 2019 - 41

electronic instruments and, per the Federal Aviation
By dint of that arrangement, losing all six flight
Administration, were required to preserve the redundancy
instruments only occurred by the long-shot failure of three
of their old panels. Actually, they needed to go further.
of three power sources - a low-odds outcome.
The early choices varied between: a full-panel upgrade
For some converts to the EFIS side, retaining some of
with new systems to preserve the desired redundancy; or
the old six-pack provides the least costly path to panel
a partial upgrade that used some of the old, heavy, analog
redundancy.
instruments to provide the needed redundancy. With the
Retaining the attitude indicator and gyro compass or
full replacement, owners upgrading to glass realized
directional gyro is one solution to going partly glass,
they'd need power redundancy as well as instrument
but prospects might want to consider adding suction
redundancy to satisfy the FAA - and common sense.
redundancy to assure continued airflow through those two
That issue also arises in partialimportant instruments.
panel upgrades or whenever an
But that suction pump remains a
operator removes the air pump -
driver behind many pilots' decision
originally installed to power two of
to go partially glass. Some of those
TODAY, WITH YEARS
the air-driven gyros common to the
pilots opt to replace the air-driven
OF GLASS-COCKPIT
old standard six-pack - in order to
AI with one powered by the ship's
ADVANCES BEHIND
electrical system.
use the drive pad to turn a standby
US, SATISFYING THE
alternator.
Removal of the suction pump
OPTIONS AVAILABLE
When all the flight instruments
opens up that drive pad for the
FOR BOTH POWER
run on electricity, electrical-system
installation of a standby alternator
AND
INSTRUMENT
redundancy rises in importance.
of the type made by B&C Specialty
REDUNDANCY
Today, with years of glass-cockpit
Products in Newton, Kansas. The
advances behind us, satisfying the
company's STC'd 20-amp standby
options available for both power
alternators are installed in new
and instrument redundancy is at an
Textron Aviation Bonanzas, both
all-time high.
G36 and G58 twins. They're a
Let's highlight some of the many
popular option for the A36 and
options for adding depth to the
33 Bonanza models, along with
panel's redundancy. This overview
controllers for both 14- and 28-volt
looks at both electrical-power and
systems.
flight-instrument redundancy options.
B&C also offers the same alternator in an STC'd
package for the Cessna 210 and Piper PA-32, Lance,
Keeping electrons flowing: ElectricalCherokee Six and Saratoga.
system need increase with glass panels
Should the main-ship alternator fail in-flight, the
The typical six-pack panel of earlier years had a simple
controller senses the voltage drop and automatically
genius to it: three air-data instruments, three gyroscopic
activates the standby alternator. If the load on the system
instruments.
exceeds 20 amps, upon activation of the standby alternator,
Five of the six need only air pressure: airspeed;
a panel-mounted annunciator light begins to flash.
altimeter; vertical speed, all plumbed to the pitot-static
That annunciator signals the pilot to reduce the current
system; and attitude indicator and gyro compass, both
load to no more than 20, at which time the annunciator
stops flashing and burns steadily. This approach allows the
powered by airflow. Producing that airflow: either a drypilot to select what equipment to switch off and what to
air suction pump or a wet positive-pressure pump.
keep.
The sixth instrument and third gyro: the venerable turn
coordinator or in some planes, turn-and-bank gyro. This
In turn, with the standby alternator online, the maingyro typically spins off the electrical system.
ship battery conserves energy for the surge from such
Note how the very design of the panel split the power
Continued on following page
requirements between electricity, air pressure and air flow.

IS AT AN
ALL-TIME
HIGH.

avionics news

may

2019

Avionics News May 2019

Table of Contents for the Digital Edition of Avionics News May 2019