Falcon 10X

[ATLcrew]

Yes, it is a hydraulically-driven generator.

But then how would the...never mind, let's see what I hear from above first.

[Evan]

That's even weirder as that would imply the RAT drives the emergency gen hydraulically. That may very well be the case, but I was not aware of that. Still waiting to hear from my Fleet Chief.

Yes, it is a hydraulically-driven generator.

[ATLcrew]

That's not the RAT itself being shed, it's the emergency electrical generator. If something has to go, it would be this rather than essential flight control hydraulics. That still leaves you with the battery, so you don't lose essential electrics either.

That's even weirder as that would imply the RAT drives the emergency gen hydraulically. That may very well be the case, but I was not aware of that. Still waiting to hear from my Fleet Chief.

[Evan]

I have placed an inquiry with my Fleet Chief on this. My schematic does, in fact, looks the same as that one. What gives me pause is that the RAT is on the same side of the Blue priority valve as the slats, so that suggests to me that the slats would NOT be shed. Besides, the way that schematic looks, it seems like the RAT itself would be shed, which makes no sense. So, I'll reserve further comment until I hear from my Fleet Chief.

That's not the RAT itself being shed, it's the emergency electrical generator. If something has to go, it would be this rather than essential flight control hydraulics. That still leaves you with the battery, so you don't lose essential electrics either.

[ATLcrew]

Is it possible that Airbus has changed the hydraulics architecture?

I have placed an inquiry with my Fleet Chief on this. My schematic does, in fact, looks the same as that one. What gives me pause is that the RAT is on the same side of the Blue priority valve as the slats, so that suggests to me that the slats would NOT be shed. Besides, the way that schematic looks, it seems like the RAT itself would be shed, which makes no sense. So, I'll reserve further comment until I hear from my Fleet Chief.

[ATLcrew]

FYI, this is one of the most comprehensive descriptions I have found on the A320 electrical system and protection features (PDF download):

https://www.icao.int/safety/airnavig...nal_report.pdf

Refer to section 1.6.5

I think what I was referring to might be due to the GCU differential protection function.

It also specifies:


So perhaps this doesn't apply to the ac's you are flying.

Indeed. Not only do we not have to wait to start the APU, but we also have AC ESS ALTN auto-switching which BA apparently does (did) not.

[Evan]

I am almost sure that that is incorrect and that Cactus had already been completely cleaned up before hitting the birds.
"Lifted off with flaps 2 and ditched with flaps 2" does not imply that "no flap changes were made" (not that you said so though)

OK, found the CVR. You are correct about that. Birdstrike occurred about a minute after flaps 1 call and after they cleaned up. I mistook the F/O query to 'stay' at flaps 2 to mean they never reconfigured.

[Gabriel]

First of all, Cactus 1549 lifted off with flaps 2 and ditched with flaps 2. No flap changes were made.

I am almost sure that that is incorrect and that Cactus had already been completely cleaned up before hitting the birds.
"Lifted off with flaps 2 and ditched with flaps 2" does not imply that "no flap changes were made" (not that you said so though)

[Evan]

Out of curiosity, where did this come from? There is nothing in my manuals that says that. Now, it takes 50 seconds to a minute for the APU to actually spin up, but I see nothing that says I have to wait 45 seconds to initiate the APU start sequence.

FYI, this is one of the most comprehensive descriptions I have found on the A320 electrical system and protection features (PDF download):

https://www.icao.int/safety/airnavig...nal_report.pdf

Refer to section 1.6.5

I think what I was referring to might be due to the GCU differential protection function.

It also specifies:

The A320 family aircraft Electrical Power Generation System (EPGS) has undergone design changes with time, giving rise to two distinct con gurations of EPGS. The original is referred to as the ‘Classic’ con guration and the more recent as the ‘Enhanced’ Electrical Power Generation System (EEPGS). The EEPGS was introduced on production aircraft through Airbus Modi cation No 27140. G-EUOB was equipped with the ‘Classic’ EPGS.

So perhaps this doesn't apply to the ac's you are flying.

[Evan]

There is nothing in my manuals re slat shedding or priority valves.

Is it possible that Airbus has changed the hydraulics architecture?

[Evan]

Out of curiosity, where did this come from? There is nothing in my manuals that says that. Now, it takes 50 seconds to a minute for the APU to actually spin up, but I see nothing that says I have to wait 45 seconds to initiate the APU start sequence.

Unfortunately, I think that came from the FCOM I accidentally deleted while running a cleaner app on my very ill computer. It was deleting duplicate files so I must still have a copy but I also had to disable the finder indexing to keep it from overheating. I'm replacing it next week so hopefully I can find that FCOM again.

The issue had to do with electrical switching and some safeguard that prevent the APU generator from coming online for 45 secs. It's sort of redundant here anyway because if you follow procedure (Sully did not) and attempt a relight for 30 secs, wait 30 secs, and then attempt a second one before starting the APU, that's already well over 45 secs.

[ATLcrew]

My FCOM suggests that the RAT can provide flap extension, albeit slower to transit and will shed slats below a low pressure threshold via a priority valve (the A330 has a LAND RECOVERY switch to recover the shed slats shortly before landing).

Perhaps ATL can shed some light on this....

There is nothing in my manuals re slat shedding or priority valves.

[Evan]

I just thought of another one. They extended the slats/flaps allowing for a slower touchdown. Would they have been able to do it with just the RAT and how long it would have taken?

Ok this...

After the 'Miracle on the Hudson' there was a lot of forum discussion about how the APU start was needed to provide flaps.

First of all, Cactus 1549 lifted off with flaps 2 and ditched with flaps 2. No flap changes were made or needed. Therefore, the APU was not critical to the outcome.

Secondly, more obscurely, is the issue of flap operation with the RAT alone.
- According to my A320 FCOM and every other one I've seen, the RAT powers the Blue system and the Blue system also powers the flaps. Normally, the Blue system is electrically powered by the engines and provides 3000psi. WIth the RAT alone, it still provides 2500psi.
- According to the NTSB final report, the flaps are only powered by the Green and Yellow systems.

So which is true. It's hard to imagine different A320 builds would vary on this basic architecture.

My FCOM suggests that the RAT can provide flap extension, albeit slower to transit and will shed slats below a low pressure threshold via a priority valve (the A330 has a LAND RECOVERY switch to recover the shed slats shortly before landing).

Perhaps ATL can shed some light on this....

[ATLcrew]

They extended the slats/flaps allowing for a slower touchdown. Would they have been able to do it with just the RAT and how long it would have taken?

Yes, and longer than normal.

[ATLcrew]

There is also a 45-second delay from the time the IDG's go offline until the APU can be started...

Out of curiosity, where did this come from? There is nothing in my manuals that says that. Now, it takes 50 seconds to a minute for the APU to actually spin up, but I see nothing that says I have to wait 45 seconds to initiate the APU start sequence.