Electrical transfer after engine start

An engine start can change which source powers an AC bus. The overhead panel contains the electrical source controls; use ELEC to check the actual bus supply.

With the IDG selector in AUTO, FSS says the engine-driven generator comes online after its engine starts and replaces the previous source on that AC bus. Confirm the transfer on ELEC before removing ground power.

Initial source

Identify what supplies each bus before start.

Open ELEC and identify which source currently supplies each AC bus. Record whether the APU and AC GPU are available.

Start the engine

Use the applicable start flow and monitor engine indications.

Onside IDG

Compare onside IDG and bus indication.

Watch the electrical synoptic to see which source supplies each bus after the engine starts.

Bus tie

Observe actual tie and source states.

FSS describes automatic bus-tie operation when needed. Compare the source and bus indications rather than assuming both sides transferred together.

Remove the AC GPU

This applies only when an AC GPU is connected. Confirm that the required buses have a suitable replacement source. FSS recommends waiting 30 seconds after N2 stabilises or checking ELEC. Press the AC GPU button OUT, confirm IN USE changes to AVAIL, then disconnect the AC unit. A DC GPU is separate and is not controlled by this button.

IDG DISC

FSS describes DISC as a mechanical disconnect, separate from OFF. Use the normal procedure for routine source changes. ^{[56] [9]}