Same Airplane, Different Answer
A320 Electrical Foundation, Week 2 companion
A complex and contradictory "Before vs. After" split-screen on the exact same panel hardware to visualize the confusion pilots can face when they rely on generic, rote answers.
TL;DR
Several correct answers in the A320 electrical chapter depend on which aircraft you are sitting in rather than on the type. After an AC BUS 1 fault, aircraft equipped with AC ESS FEED Auto Switching recover the AC ESS BUS and DC ESS BUS automatically because AC BUS 2 automatically supplies the AC ESS BUS, while aircraft without it require the crew to select AC ESS FEED to ALTN when the ECAM procedure requests it. Galley shedding depth varies with the Galley Load Automatic Shedding fit. Some procedures carry separate status pages for specific registrations. And a warning may be caused by a sub bus failure, in which case only part of the listed systems may be lost. None of this is exotic. It is ordinary fleet reality, and it is the part of the chapter that generic study material structurally cannot carry, because it is not a property of the A320. It is a property of your operator's aircraft.
A type rating is a promise about uniformity.
That is most of what makes the whole system work. You learn one aircraft, you are qualified on a fleet, and the aircraft you walk out to on any given morning behaves like the one you learned. The promise is kept far more often than not, which is why it is a reasonable promise to make.
But it is not kept perfectly, and the A320 electrical chapter is one of the places where the seams show. There are questions in this chapter where the correct answer is not a property of the type at all. It is a property of the specific aircraft, and two pilots giving different answers can both be right.
Candidates find this genuinely disorienting the first time they meet it, and the disorientation is worth naming, because the instinct it produces is exactly the wrong one.
The case that makes it concrete
You have an AC BUS 1 fault.
AC BUS 1 normally supplies the AC ESS BUS and, through TR 1, the DC ESS BUS. So both essential buses are affected initially, and the corresponding ECAM faults appear. That much is universal.
What happens next is not.
On aircraft equipped with AC ESS FEED Auto Switching, the AC ESS BUS and DC ESS BUS recover automatically, because AC BUS 2 automatically supplies the AC ESS BUS. The crew watches it happen.
On aircraft without that fit, the flight crew manually recovers the AC ESS BUS and DC ESS BUS by setting the AC ESS FEED pushbutton to ALTN, as requested by the AC ESS BUS FAULT ECAM procedure. The crew makes it happen.
Same failure. Same aircraft type. Same ECAM alert. Two different accounts of what the airplane does, and both of them are correct for the aircraft they describe.
If you learned the automatic version and you are sitting in an aircraft without the fit, you will wait for a recovery that is not coming until you action it. If you learned the manual version and you are in an aircraft with the fit, you will be reaching for a pushbutton on a bus that has already recovered. Neither is catastrophic. Both are the kind of hesitation an examiner is specifically looking for.
It is not one oddity
If this were a single quirk it would be a footnote. It is not.
Galley shedding depth varies the same way. After failure of one engine generator, part of the galley load and the DC BUS Entertainment are automatically shed. But the Galley Load Automatic Shedding function, where fitted, allows all the galley load to be automatically shed, including the secondary galley. So the honest answer to what gets shed is that it depends on the aircraft standard.
That same shedding question also depends on phase and source, which is a different kind of conditional stacked on top. The main galley, in-seat power supply, and IFE are automatically shed in flight when only one generator is operating, and on the ground when the aircraft is supplied by one engine generator only. But all galleys are available on the ground when the APU generator or external power is supplying power. So the full answer carries a fit condition, a phase condition, and a source condition, and a candidate who gives only the blunt version has answered a different question than the one asked.
Then there are the status lists. Some procedures in this chapter are split into applicability groups, identified by an applicable-to line naming specific aircraft registrations before the procedure content. In one such split, a group of registrations carries a separate status page that adds an additional item to the inoperative systems list. The failure is the same. The consequences on the status page are not.
That is the manual telling you plainly, in its own structure, that one answer does not fit the fleet.
The cousin of the problem
There is a related caveat that is not about aircraft fit but produces the same failure in candidates.
For AC BUS 1 fault and again for AC BUS 2 fault, the manual notes that the warning may be caused by a sub bus failure, and consequently only a part of the listed systems may be lost.
So an examiner hands you an inoperative systems list as long as your arm and asks what you have lost. The confident answer recites the list. The correct answer recites the list and notes that if the warning was caused by a sub bus failure, only part of it applies, which is why you read the status page rather than reciting from memory.
Same shape as the fit dependency. A question that looks like it has one answer, which actually has a conditional structure the candidate is expected to know about.
Why the instinct to flatten it is wrong
Here is what candidates do when they first meet this, and it is completely understandable.
They pick one version and learn it. Usually the more common one, or the one their training provider taught, or the one in whichever study guide they happened to buy. Then they answer confidently, because confidence is what gets rewarded in most of the oral, and the conditional version sounds like hedging.
The trouble is that an examiner probing this territory is probing precisely for the conditional. The question is not asked by accident. If someone asks you what happens to the essential buses after an AC BUS 1 fault, and they ask it in a way that leaves room, they are usually checking whether you know the room is there.
A confident universal answer to a conditional question is worse than an uncertain one, because it demonstrates that the candidate does not know the distinction exists. Uncertainty at least signals awareness of a boundary.
The version that lands is not hedging. It is precise: on aircraft with Auto Switching it recovers automatically because AC BUS 2 supplies the AC ESS BUS, and on aircraft without it I select AC ESS FEED to ALTN when the ECAM asks. That is one sentence, it is completely definite, and it happens to contain a condition.
What this means for how you prepare
Two practical consequences, and they point in the same direction.
The first is that you have to know your own fleet's fit. Not in the abstract. The applicable-to lines in your operator's manual are the authoritative record of which procedures split and which registrations fall on which side. That information exists, it is not hidden, and most pilots have simply never had a reason to look for it.
The second is a limitation on generic study material, and it is structural rather than a criticism. A generic A320 resource cannot carry this content, because the content is not about the A320. It is about your operator's aircraft, and it lives in your operator's manual set. A resource built on a generic manual has nothing to draw the fit dependencies from, so it will give you the universal version of every answer, which is exactly the version that gets probed.
This is the honest argument for operator-specific preparation, and it is worth stating in technical terms rather than commercial ones. The reason an operator-specific tool can answer these questions is not that it is better written. It is that it is built on the manual that contains the applicable-to lines.
The underlying discipline
Strip away the electrical specifics and there is a general habit here worth carrying into every system.
The manual attaches conditions to most of its statements. The conditions are not decoration and they are not there to be paraphrased away. When you learn a fact from this chapter, the useful question is not only what does the airplane do, but under what condition does it do that, and what happens in the case the condition excludes.
The APU generator replaces a failed engine generator if it is available. Crew awareness sometimes means monitor and continue and sometimes follows a directed selection. A reset attempt exists, and for a differential fault it has no effect after two attempts. Galleys shed, depending on phase, source, and fit.
Every one of those is a fact with a condition welded to it. Learn them welded together and the chapter gets simpler, not harder, because the conditions are what make the individual facts stop contradicting each other.
Where this sits
This is a companion piece to Week 2 of the A320 Electrical System Foundation Series, which covers single source loss and the automatic reconfiguration that follows. The generator fault and IDG disconnect questions are set out in question and answer form on the Week 2 page. The full walkthrough of all four controls is in the companion article.
Week 1 covers the normal architecture, the source priority hierarchy, and the external power indications. Week 3 covers emergency electrical configuration, the RAT, and battery-only operation.
Prepare with citation-grade answers
The Custom GPT Solutions A320 Oral Exam Preppers walk the reconfiguration logic, the conditions attached to every published answer, and the aircraft-fit dependencies that change the correct answer between tail numbers. Every answer cites the exact FCOM, FCTM, AFM, or QRH passage so it can be verified against your own operator library.
Operator-specific variants are live for Wizz Air, Air Arabia, Hong Kong Airlines, Ryanair, and flydubai, at six dollars per month, and they are built on the operator manual set rather than on a generic A320 reference. Generic A320 and B737 tools sit alongside them. First week free.
