EXTERNAL POWER: CONNECTED, AVAILABLE AND SUPPLYING
The engines can be stopped while the cockpit remains fully powered. At the gate, one possible source is a ground-power unit, often shortened to GPU. It supplies electricity through a ground connection. On the overhead, EXT PWR AVAIL means the aircraft recognises a suitable available source. Selecting EXT PWR requests its use. These are two different stages: someone can connect an acceptable source before the aircraft has selected it. When learning the sequence, pause long enough to recognise availability, then make the selection and watch for the change. [22, PDF pp. 4, 6]
The lower ECAM screen's ELEC page helps show what happened. ELEC is simply the electrical-system page. Its diagram connects the sources to buses, the distribution points that carry electricity to groups of equipment. AC means alternating current and DC means direct current; the aircraft uses both, with equipment that converts between them where needed. At first, follow the intended main source through the diagram to the supplied buses. You do not need to memorise every branch to ask a useful question: is the connected source actually providing the power that this part of the aircraft needs? [22, PDF pp. 2–8]
The two batteries have a supporting role in the electrical system. Establish their required normal AUTO selections and inspect the available indications, then confirm the intended main supply. A cockpit that has lit up on limited battery power is not a reason to leave it running indefinitely without the appropriate supply. Give the computers and displays time to finish their normal startup. A screen changing during that sequence needs to be read in context, rather than immediately treated as a lasting fault. You will shortly use the powered displays to prepare the rest of the aircraft. [22, PDF p. 5] [19, PDF p. 4] [14, PDF p. 1024]
For the Frankfurt exercise, separate the observations. First, the source becomes available. Second, you select it. Third, the ELEC page confirms the resulting supply arrangement. The ground vehicle, the AVAIL light and the powered diagram each tell you something useful, but none alone tells the whole story. Once you can recognise those stages, the same reasoning will make the later transfer to APU power much easier to follow. [22, PDF pp. 4, 6]
BAT 1, BAT 2, APU GEN and EXT PWR in the original overhead reference. [23, PDF p. 1]
IN PRACTICE: External power: availability and actual supply
Before you begin: Initial control checks complete. The aircraft is parked and a simulated ground-power service is available. Use a stable supply for the following preparation.
1. Connect the ground source
Action. Use the chosen Fenix ground-service workflow to connect the ground-power unit. Wait for EXT PWR AVAIL on the overhead before selecting it.
Check. The aircraft recognises an acceptable external source. A visible vehicle or cable has been followed by the aircraft’s own availability indication. [14, PDF pp. 988-999] [22, PDF pp. 7-9]
2. Select the normal battery state
Action. Set BAT 1 and BAT 2 to their normal AUTO selection and inspect the available voltage/charging indications. If the starting state has a battery-related fault, resolve that state through the appropriate current procedure.
Check. The normal battery selection and indications are established without adopting an arbitrary voltage limit from an unrelated example. [14, PDF pp. 988-999] [22, PDF pp. 21-22]
3. Select external power
Action. With AVAIL present, select EXT PWR ON. Observe the change in the pushbutton indication and the appearance of powered equipment.
Check. The source has been selected and the aircraft begins receiving power. Availability and selection have been distinguished. [14, PDF p. 989]
4. Trace the electrical supply
Action. Call the ECAM ELEC page. Identify EXT PWR and follow the displayed connection to the AC distribution, then inspect the associated DC/battery indications and any abnormal flags.
Check. The distribution page confirms which source is actually supplying the aircraft; screen illumination is only part of that confirmation. [22, PDF pp. 2-5] [22, PDF pp. 7-9]
5. Wait for usable equipment
Action. Allow the normal display/computer initialization to finish. If a MCDU PLEASE WAIT message is present, wait for it to clear before starting data entry, then continue the preparation.
Check. The equipment is ready for the next task. A running initialization sequence has not been disturbed by repeated selections. [14, PDF p. 1022]
Complete when: External power is connected and selected, the distribution page confirms actual supply, and the aircraft has completed its normal power-up sequence.