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?

re from 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

Max Reverse

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

Thanks

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

@ 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

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 ...

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

@ 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

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: