The magnetic pickup provides speed signals to the
electronic sequence unit (ESU) in the aircraft.
A single harness connects all electrical
of the APU to the Main electrical connector.
to the aircraft electrical system
is through this main electrical
to the harness. Refer to schematic for electrical harness
The ignition exciter
is a capacitor-discharge
converts direct-volts input to a high-potential
alternating voltage for ignition.
The ignition cable connects the ignition system to
the igniter plug.
A shunted-gap type igniter plug provides the igniter
for initial ignition of fuel during start of the APU.
A single-element, chromel/alumel thermocouple is part
the electrical harness.
senses exhaust gas
temperature (EGT) and provides the signal to the ESU. The output
signal is used by
the ESU for overtemperature protection, shutting
down the APU if EGT exceeds safe limits.
The meter assembly provides accurate tracking of APU
hours and number of starts for purposes of maintenance,