Using the APUs

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Last updated Dec 2, 2007

This file tells how to use the APUs at Squadron 2, NMWG CAP, Albuquerque NM, to power the GA-8 and the C-182T.

Background

APUs (Auxiliary Power Units) are pieces of equipment used during ground maintenance to power an aircraft from an AC wall socket to prevent draining of battery power. They can also be used to supply power during ground tests of electrical systems and ground training sessions for electronic systems. The APUs have a cable which connects to a socket on the aircraft.

We have two APU types: (ONE) GRAY APU and (TWO) RED APUs. The two types are NOT interchangeable.

USE OF THE WRONG APU ON A PLANE CAN CAUSE DAMAGE!

For safety, keep the propeller arc clear when the APU is connected to the airplane.

Procedure for GA8 and the GRAY APU

The gray APU is marked GA8. It's a 12V APU because the GA8 is 12V.

Set the APU to "Power" (Do not set it to "Charge")
Connect the APU to AC power
Plug the APU output cable into the fitting on the aircraft. The socket is below the pilot's door.
Turn the APU power switch on. The GA8 external power relay will "click", closing the connection between the APU and the battery.
To operate the avonics, make sure the circuit breakers on the floor (2,1,2) are pushed in. Note we are normally leaving them pushed in now.
Turn on the Master Switches for Buses 1 and 2
Turn on the Avionics Switches 1 and 2 to use the avionics.
Make sure you don't turn on the fuel pump.

Procedure for C-182T and the RED APUs

Set the APU (either RED APU) to 28 volts.
Connect the APU to AC power
Plug the APU output cable into the fitting on the aircraft. To open the aircraft external power access door on the left side of the engine cowling, you need a Phillips-head screw driver.
Turn the APU power switch on.
Confirm Avionics buses 1 and 2 and the standby battery are off.
Turn on the Battery Master Switch. The Battery Master Switch must be on for the battery to receive power from the APU. This also sends power to the electrical buses including the "essential" bus, so the PFD and other essential avionics are on.
To operate the avionics, turn on Avionics buses 1 and 2.

Shutting Down

When finished with the avionics, reverse the process above, and once the APU power plug is removed from the aircraft, make sure the aircraft external power access door is secured and locked.