All GEN Fail on A320?

[Founder]

If all generators on an A320 fail and the A/C is above 100 kt the RAT sould automatically extend, while it is extending which is about 8 seconds the batteries power the emergency generation network.

My question is this: is there any indication that the RAT is powering the emergency network or how do you know that the RAT has taken over the task of powering the network from the batteries?

Kind Regards
Tim

[Mäx Reverse]

I found this one very helpful: As soon as the L/H ND comes back on, the EMER GEN is on line!

Regards, MAX

[Founder]

Yea but do you get an ECAM message that the RAT is exteded? or how can you tell if the EMER GEN is powered by the batteries or RAT?

Kind Regards
Tim

[Mäx Reverse]

Flight On Batteries: All Eng/Apu GENs have failed and the EMER GEN is NOT on line. You only have HOT BAT BUS 1+2, parts of DC ESS BUS via BAT2 (parts are shed) and parts of AC ESS BUS via ST INV and BAT 1. My Reminder: LH ND is OFF!

EMER ELEC: All Eng/APU GENs have failes but the EMER GEN is on line. You now have AC and DC ESS Bus and off course the HOT Busses powered. My Reminder: LH ND is ON as it ist powered by the AC ESS SHED BUS, which is now on again!

Note: The EMER GEN can only be powered by the RAT via the BLUE HYD system.

If the RAt is extended, you get a status reminder 'RAT OUT' on the E/WD. But RAT extended does NOT have to mean the EMER GEN is operating.

OK?

MAX

[Founder]

"If the RAt is extended, you get a status reminder 'RAT OUT' on the E/WD. But RAT extended does NOT have to mean the EMER GEN is operating."

As I understand it from FCOM Vol 1 Electrical page 13, the EMER GEN can be powered by either the RAT or BATTERIES.

but you did tell me what I wanted to know by saying this:

"you get a status reminder 'RAT OUT' on the E/WD"

Thank you for your quick reply and good help =)

/Tim

[Mäx Reverse]

As I understand it from FCOM Vol 1 Electrical page 13, the EMER GEN can be powered by either the RAT or BATTERIES


No, the EMER GEN is hydraulically driven, (only) via the RAT and the Blue Hydraulic.

Take a look at p.3 There it says: The blue hydraulic circuit drives an emergancy generator that automatically supplies emergency AC power to the aircraft electrical system if all three main genartors fail...

Airbus philosophy is that flight on batteries is only a transient condition, so no way to power the elec system to EMER Level by Batteries.

What are you doing? Transition to A320? If so from which aircraft? Other Manufacturers see 'Battery Power Only' as EMER Level and 'Stanby Generator' as ESS Level, so be cautios to understand AI terminology.

Cheers, MAX

[Founder]

I'm prepearing for my first TR in about 1,5 months so I'm trying to understand all the system prior to attending the TR.

I should have written the EMER GEN NETWORK and not only the EMER GEN...

a note on page 13 Electrical sais the following:
"During RAT extension and emergency generator coupling (about 8 seconds), the batteries power the emergency generation network..." But this is only a temporary transition as far as I can understand.

Also on that page it sais:
"If the RAT stalls or if the aircraft is on the ground with speed below 100 knots, the emergency generator has nothing to drive it. The emergency network transfers automatically to the batteries and the static inverter and the system automatically sheds the AC SHED ESS and DC SHED ESS buses."

Doesnt that mean that when all options are lost to generate power, the aircraft resorts to the final source of power, the batteries?

Have you flown the aircraft a lot?

Kind Regards
Tim

[Mäx Reverse]

Also on that page it sais:
"If the RAT stalls or if the aircraft is on the ground with speed below 100 knots, the emergency generator has nothing to drive it. The emergency network transfers automatically to the batteries and the static inverter and the system automatically sheds the AC SHED ESS and DC SHED ESS buses."


THAT's the key to understanding the difference! The same happens in the air until the EMER GEN gets on line.

The main reason for this split into AC/DC ESS BUS and AC/DC ESS SHED BUS is to reduce the load on the batteries, as this condition is by AIs definiton only temporary (if reality knows about that may be another question).

Be aware: The system behaviour during RAT operation varies greatly depending on the age of the aircraft. Older aircraft 'lose' the RAT already below 140 knots (that means the entire final approach is on batteries only - so treat them nicely), while the newer rat stalls only at 100 knots during roll out.

Also on the older aircraft you'll have a CRM-Masterpiece in this case: Do you try to start the APU or not? If it works, you're back in business, if it doesn't, will your batteries last for the approach??!

During your training you will discover some more edges in the design which will leave you wondering who on earth designed and certified that, but that's the way it is. Look at the same feature on the A330/A340 and you'll be surprised...

Im A320 rated for 8 years after flying a nice, little, british 3-Engine-High-Wing for 4 years... :)

Good Luck, MAX

You may PM me anytime if confusion grows. And remember: It's not a bug, it's a feature:}

[Founder]

ahaaaaa... now I see =)

Well that APU question is pretty obvious, you don't gamble with the only thing you have left... right? =)

I know a captain at mytravel and he also gave me the heads up on the older A320's running with the 140 kt limit but he also said that they are probably being updated to the 100 kt limit, do you know anything about that?

I could sure any help I can get, your help is much appreciated, thank you =)

Do you by any chanse know anything about the Job market for pilots in Europe and perhaps anything about Sabena Flight Academy? That's where I'm most likley going to do my TR on the 320...

Kind Regards
Tim

[Mäx Reverse]

As far as I know, no modification planned at out company.

And sorry, but no infos about that Sabena School.

CU, Max

[ayedaldosary]

you should have many attention getters the first one is your common sense (no offend) second : overhead emergency elec panel lite fault lite will come on if the rat did not deploy

[Founder]

Since I'm pretty new at this aircraft, just started to study it and I hadn't reached the chapter which handles the buttons on the over head panel yet =) so no, I didn't know that button excisted =)

[aulglarse]

Hey Founder,
I agree with previous posts.....Having just completed the last sim cycle with dual gen failure:uhoh: where it took a few seconds to re-establish emer power, you will be a tad busy hand flying with your offsider cancelling the master warning/caution (more than once I tell you! ) before you will realise the RAT has extended! Apart from pre-mentioned S/D "rat extend" Just check the ECAM elec page to see the power configuration.
When you get your FCOM's, the QRH will give you what systems you have remaining in EMER ELEC CONFIG.
Best of luck!:ok:

[Founder]

Thank you =)

[jorel]

interesting as mentioned flight on batteries could be a scenario you end up with, is there any mention anywhere of how long you could expect the batteries to last

[aulglarse]

The A320 is certified to have approx 60mins on emergency battery supply.

Trying to start the APU on batteries alone reduces this time ( by approx 3 mins, I think..to be corrected if so, for every attempted start) so you'll want to be within 60 mins of the nearest suitable airport before things go dark.

One sim check involved DC 1+2 FAULT which meant you couldn't start the APU because the batteries were not available-no DC BAT BUS:uhoh:

[Coffee Black None]

Start the APU on bat only?

In the QRH 1.01 Elec Emer Config Sys Remaining it says that the APU ECB-STARTER only is available when the RAT is running. It says INOP when on BAT ONLY in flight en is only restored ON THE GROUND when speed is below 100 knots.

Can you explain me how you can start the APU in flight on BAT ONLY?

[captain87]

As Coffee Black None says,
it's impossible to start the APU on BAT only in flight;
this to preserve the batteries in case of an APU start fault and a RAT stalling at the same time. In this case we will have no generators supplying all the buses. Once the RAT ceases to supply the ESS AC and DC below 100 kts, the battery power takes over until reaching 50 knots ...
Furthermore the APU can be started on batteries only on the ground, since the complete lost of electrical power would be less serious.
The minum battery voltage is 25.5 but the batteries cannot discharge below 22.5 to allow an eventual APU starting.
This has been programmed by Airbus as system logic ...

Kind regards !

[Mäx Reverse]

@ aulglarse

The A320 is certified to have approx 60mins on emergency battery supply.

In our ships we have two 24V and 23Ah Batteries which are according to me book good for only 30 Minutes of Emergency Power.

Regards, MAX

[captain87]

Yes, precisely from 22 to 30 minutes according to the battery load.
It's important to remind that the batteries voltage doesn't drop below 22.5 v, to allow an eventual APU starting attempt.

Regards

[Coffee Black None]

What happens if there's a time gap between RAT stall on approach at say, 140 knots on unmodified A320's and 100 Knots on the ground?

For that matters, when does the RAT stall on A319's? 125Knots?
Is there a "guarenteed" speed on modified A320's/A319/A321?

[captain87]

If the RAT stalls or if aircraft is on the ground with speed below 100 Kts, the emergency generator has nothing to drive it.

The RAT stalling speeds for the different types are:

A319: less than 125 kts
A320: less than 140 kts / less than 125 for modified A320
A321: less than 125 kts


Note: This speed limit is for electrical power and the RAT will continue to supply hydraulic power to much slower speeds.

Regards

[jorel]

Max Reverse

would you have a reference on the expected duration on batteries... could'nt find it in FCOM

Thanks

[Dani]

What has been written is all correct. Just to understand: The new RATs have a variable pitch propeller, that's why they are still turning fast enough on lower speeds. A318/9/21 all have the new RATs.

Dani

[Mäx Reverse]

@ jorel

Unfortunately no FCOM Reference that I know of.

I recalled this figure from a handout for a Sim-Refresher.

We do 4 SIMs a year, 2 Checks and 2 REFs. Each REF has a special topic (here: ELEC) and and excellent handout (sometimes 100 pages and more) with a lot of 'nice to know' infos contained.

That's where my figure of 30 Minutes comes from.

Regards, MAX

[john_tullamarine]

I can't speak to the Airbus specifically but 30 min is a typical design standard consideration. Generally, if the OEM bookwook doesn't quote a figure it would be reasonably safe to presume around 20-40 minutes depending on load.

It is for just this consideration that some of us don't do the typical sim electrical failure - reposition - standby power ILS .. far better to have crews faced with the time management problems of the aircraft recovery.

Generally it only takes one run to get the message across ...

[jorel]

Thanks Max reverse,

Interesting that you get four sim sessions in a year what is a ref session ?

My question about the batteries comes from an interest on A320's that have a single power source for the standby horizon that comes off the DC Essential Bus

I believe there has been an incident where it was not possible to power the DC essential bus, G-EZAC but that PFD 2 was available for attitude information

Thinking worst case scenario and linking it in to the BA incident where G-EUOB
lost all 5 screens but were eventually available to select AC Ess Feed and re power DC ESS bus. Airbus have designed a scenario where flight on batteries gives you potentially 30 minutes attitude information and that would be it.

Thinking along those lines, I have a few questions

1.In the case of G-EZAC where flight continued without DC ESS bus and the Aircraft was of the design of a single power supply to the Stanby horizon (which I believe has changed with the introduction of an ISIS display). Would the horizon of toppled by the time they had landed?

2.What is the logic for the selection of Batteries in Flight configuration?

3.If it was'nt possible to power both AC and DC ESS bus but AC2 was available, would there be a consideration for manually selecting EMER Elec?

Thanks

[Mäx Reverse]

@ jorel

I'm sorry, I don't see your point.

Let me try this:

As per design and certification it is NOT possible to loose the AC/DC ESS Busses unless you have a AC/DC ESS BUS Fault.

If you lose all GENs, the AC/DC ESS Busses are powered by the batteries (and the Static Inv) until the RAT and thus the EMER GEN take over. An ALL GENs Fault AND the EMER GEN not working at the same time such unlikely, that it is not looked at during certification.

What happened during the Incidents on G-EUOB and G-EZAC was outside certification standards with double or even multple failures within one system and may lead to a modification once the cause for the fault is determinated by the investigation.

Regarding your questions:

1.) If the Stby-Horozon loses it's (only) power-supply it's indication is usless as hopefully indicated by a warning flag. The flag should show immediately and it won't take long until the gyros lose enough RPM for the indication to become erratic.

2.) I don't understand, do you mean FLIGHT ON BATTERIES only? One BAT is supplying DC ESS BUS and the other AC ESS BUS via the Static Inverter. What would you suggest?

3.) You mean an AC BUS1 Fault AND the ESS ALTN FEED does NOT work? Well once again you become a test pilot, as this condition is not mentioned in the books. It's an emergency an the Commander may do whatever is necessary in his opinion to bring the flight to a happy ending.

It MAY help, however you will lose AC BUS 2 as well when selecting EMER ELEC manually to ON. Greatly depends on the cirmcumstances if you ask me, if the weather is ok and you can land rather soon, I rather would not try.

Regards, MAX

[idg]

I'm not sure that ALL 321s had the 'better' RAT as standard from production. If memory serves correctly we had an early one that was modified to the later standard on arrival with us from the original operator.
What I am sure of though is that when I look at the overhead circuit breaker panel and there are yellow collared c/bs present then I have a 'old' RAT a/c.
Interested to hear that the later RAT has a variable pitch propellor though. How did the early system maintain 3000psi when at high speed I wonder?:hmm: