Avionics News May 2013 - 23

Another alternative: an air-driven alternator that drops
down from a hidden compartment upon the loss of the
main alternator.
Various approaches to these second-source solutions are
eligible for retrofit under supplemental type certificates.
A Battery of Redundancy:
Integral Batteries Keep Systems Alive

Increasingly, avionics makers are addressing the wisdom of a standby power source in their retail products.
Aspen Avionics, for example, offers most of its Evolution
1000 packages with an integral backup battery.
Mid-Continent Instruments and Avionics offers the True
Blue Power line of stand-alone batteries capable of powering most glass and analog stacks and the radios that use
them.
Additionally, L-3 Avionics Systems’ J.E.T. emergency
power supplies provide power to operate two to three essential aircraft instruments.
A number of STCs exist for adding redundant power
production from other companies, among them Basic Aircraft Products BAE-14/28 Auxiliary Power Supply and the
company’s BPE-14 Turbo Alternator.
These systems offer pop-out power from small alternators attached to a wind turbine and mounted in a housing
that hides inside the fuselage or wing. Deploy when needed and get up to 18 amps of power when needed.
And then there’s the AvTek solution: a portable battery
that powers aircraft electrical-system busses through a hot
power-plug socket in the panel.
The AvTek package employs deep discharge, rechargeable, batteries; these are sealed and maintenance-free cells
with no maintenance required. Nothing can get out, and
there is nothing to add. Simply plug into the cigarette or
power-supply socket wired to the aircraft’s main bus and
turn on the power. AvTek claims an hour of power when
the load is managed.
More than a few pilots with the AvTek battery managed
to keep the lights on – along with other avionics necessities – for more than a half-hour after the failure of the
alternator or generator.
Such a portable-power source translates as the third
electrical system for some aircraft of the 1960s and early
1970s. All are comprised of a generator or alternator, a
generating source (alternator or generator) and a main battery; add a permanent or temporary battery and give the
rescue people about 30 more minutes.
With redundancy, should that unfortunate emergency
finally arrive, both the pilot and aircraft are better-prepared to produce an outcome only slightly memorable or
eventful. q

Keeping Old
Instruments
Spinning
Air-Powered Gyros Work Well –
But Only as Long as the Air Flows
In a panel with the conventional instrument
diversity of more than 50 years ago, both the attitude indicator and directional gyro used air for
power – atmosphere sucked through each instrument’s air turbines and spinning the gyro mass.
The turn indicator gyro ran similarly – but
powered by an electric motor.
Losing radios and lights in instrument meteorological conditions is not fun. But at least an
electrical-system failure leaves the pilot with
the majority of the gyro functions – the AI and
DG, still working.
Lose suction power and the two gyros mostcritical to instrument flight quickly lose their
way.
Those two together greatly reduce the partial-panel flying demands.
For years, suction-pump failures factored into
an average of two fatal accidents annually. So
for all those not yet moving to all-glass, suctionsystem redundancy is the smartest money a pilot can spend.
Some aircraft have been fitted with dual suction pumps; the common approach for suctionsystem redundancy remains one drawing air
through the gyros with engine intake-manifold
suction or with a second pump driven by an
electric motor.
The standby pump and motor face one limitation that causes some pilots to go with the
engine-suction approach; the standby pump
needs electricity. But the engine produces suction through the intake manifold as long as it
turns – even when merely wind-milling.
With a standby suction system and the main
battery, the aircraft now enjoys one standby
option for both needs – just remember the battery’s limitations and the logic of an independent standby power source. q
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Avionics News May 2013

Table of Contents for the Digital Edition of Avionics News May 2013