System Description
© 2018 Avco Corporation. All Rights Reserved
Page 6
October 2018
TEO-540-A1A Engine Installation and Operation Manual
The Power Box supplies regulated, conditioned 13.8 VDC power through primary and secondary
channels to the ECU, ignition coils, and warning annunciators. Each Power Box channel is identical
and independent of the other and corresponds to the primary and secondary channels of the ECU.
Each Power Box channel can provide sufficient power to operate the EECS through its
corresponding ECU channel if one Power Box channel fails.
Each channel of the Power Box can get power from either the airframe-supplied 28 VDC or the
engine-driven Permanent Magnet Alternator (PMA) which supplies three-phase AC power. The
PMA is driven from the engine’s accessory housing and is the dedicated source of primary power for
the Power Box. The Power Box selects the applicable power source for the EECS either from
airframe power or the PMA. The Power Box can only use power from one source at a time and
cannot get power from both sources simultaneously.
Airframe power only is used under the following conditions:
•
During engine start
•
When the engine speed is below approximately 1000 rpm
•
When the PMA has failed.
Each Power Box Channel has a dedicated ground connected to a common airframe ground.
Electrical Interface
Table 1 identifies elements of the electrical interface for the engine.
Table 1
Engine Electrical Interface
Element
Description
EECS electrical input power requirements
Must have a supply voltage of between 12 and
28 VDC. The EECS must have airframe electric
power for start-up and as a redundant back-up to
engine power from the EECS-dedicated PMA.
NOTICE:
The minimum usable voltage for the
system is 10.5 VDC.
Interface
The airframe power is supplied to the EECS
through a four-pin plug on the wiring harness.
Wiring Harnesses
There are two wiring harnesses:
•
Engine-to-firewall wiring harness - attaches to the engine and connects to the airframe
interface wiring harness through firewall connectors.
•
Airframe interface wiring harness - supplied by the airframe manufacturer, connects the
engine harness to the ECU and Power Box as well as supplying aircraft power to the Power
Box, it is the engine-to-operator interface for airframe avionics, Ignition switch, etc.
