EIU - Engine Information Unit
The Engine Information Unit (EIU) gathers data by reading various sensors both
in-front-off and behind the aircraft's firewall and sends the processed data via
both RS232 and CAN interfaces to cockpit displays (EFIS), flight-recorders (black-boxes)
and telemetry systems.
EIU measurements include:
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Three Temperatures
using standard K-type thermocouple probes. Can be used for inner-turbine
temperature (ITT), oil-temperature and outside air temperature (OAT).
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Three Pressures
using standard 4-20mA pressure transducers. Can be used for torque, oil-pressure
and fuel pressure.
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Two Speeds
using tachometer generator signals. Can be used for gas-generator speed (N1) and
propeller speed (N2).
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Four Fuel Quantities
using any variety of either frequency based, voltage based or resistance based
quantity probes.
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One Fuel Flow
using industry standard pulse / frequency based flow sensors providing both flow
rate as well as totalizing capability.
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Battery Voltage and Current
using a 50mV shunt. Measures current in both directions.
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Eight Annunciation Switch Inputs
that can measure various conditions. On the Walter turbine they can be used for
ISOL, EHT, Hydraulic Pump, Low Oil Press, Beta (propeller), Forward and Aft Chip
detects as well as Gen Fail annunciation.
The EIU provides separate and independent power to each sensor requiring external excitation.
This prevents any single sensor (or wiring) failure causing the loss of more sensor measurements,
which can be found on systems employing common sensor power busses.
The power to each sensor is also limited in order to contain possible faults.
Such faults whether caused by a bad sensor or faulty wiring are also detected and reported by the EIU.
Installation is made easy and simple through the use of a single 50-pin standard d-sub connector
on the side of the unit as well as through the
Windows based EIU Link software
which makes configuring, calibrating and verifying correct EIU operation easy.
Calibration (or mapping) of the four fuel tanks are done in one simple operation -
filling an empty tank in stages (at user's discretion) until full only once.
These calibration settings may also be adjusted after the initial calibration operation.
Temperatures
The EIU is able to measure temperatures ranging between –60 °C and +1100 degrees
Celsius using standard K-type thermocouple probes. Thermocouples used for
measuring turbine temperature (eg. ITT) are normally supplied with the engine,
but thermocouples used for measuring Oil Temperature and OAT may need to be
obtained separately.
Pressures
The EIU measures pressure using standard 4-20mA transducers. This method
simplifies wiring by only requiring 2 wires (signal + ground) for each
sensor instead of the usual 4 wires per sensor. They also provide excellent
performance in noisy environments. These sensors are standard off the shelf
items that can be obtained in various pressure ranges.
Speeds
Both the gas-generator speed (N1) and the propeller speed (N2) can be measured
by the EIU. Tachometer-Generators provide signals in a fixed frequency-to-speed
ratio and are normally supplied with its engine.
Fuel Flow
Fuel flow sensors normally provide a fixed number of pulses per volume of fuel,
which is also called the K-factor. These pulse or frequency based flow sensors
can be read by the EIU to not only provide the flow rate, but additionally keep
track of the total volume (gallons) of fuel that passed through the sensor.
Fuel Quantities
The EIU can measure four fuel tank quantities using any combination of frequency
or voltage or resistance based fuel probes available.
Voltage and Current
Both the aircraft battery’s voltage and current can be measured by the EIU with
the use of a 50mV shunt between the battery and the electrical bus. Shunts from
as low as 5 Amp to as high as 300 Amp (@ 50mV) can be used (updating of EIU
configuration is required). The EIU will measure currents into the battery (charging)
to the value of the shunt in use (eg. 300 Amp with a 300 Amp shunt). Currents
flowing from the batteries such as encountered when cranking the engine at
startup can be measured to 5 times the value of the shunt in use (eg. 1500 Amp
with a 300 Amp shunt). Reading of the cranking current provides useful feedback
as to the battery’s strength and health.
Annunciation Switches
The EIU can detect 5 grounding switches as well as 3 positive (B+) switches. On
the Walter turbine they can be divided as follows:
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Negative (grounded) detection - Oil Press, Beta (propeller), Forward and Aft
Chip detects and Gen Fail.
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Positive detection - ISOL, EHT, Hydraulic Pump.
TSLM and FSM Inter-operation
When an on-board TSLM system is connected to the same CAN bus as the EIU,
the EIU will relay the TSLM's ITT reading to the EFIS and in this way provide measurement redundancy.
Similarly, by connecting a FSM system to the EIU's CAN bus the EIU will relay the FSM's fuel pressure and
fuel quantity measurements to the EFIS instead of it's own reading. This feature maybe used to reduce or
simplify wiring.
