I believe they turned on the APU as well as an extra electrical power source.

On an Airbus, will the gear still be operative with the loss of both engines and therefore electrical power and hydraulic pressure? I read in a newspaper that the gear in this instance couldn't be extended but it was just mainstream media so I'm skeptical because I haven't read that anywhere else. I'm thinking the pilots deliberately didn't extend the gear for the emergency landing in the field since it could possibly sink into the ground at touchdown and destabilize the landing or even be ripped off? Also, the report in the Aviation Herald says both engines were shut down just prior to touchdown so it seems while obviously not operating normally, they would still have provided power to the aircraft. I'm not sure if there was sufficient time for the APU to entirely spool up. In any case, I think they would have used manual gear extension (unless that takes a long time to extend the gear, no idea myself) if everything else didn't work so it seems the gear up on landing was intentional.

1 hour ago, threegreen said:

On an Airbus, will the gear still be operative with the loss of both engines and therefore electrical power and hydraulic pressure?...

Again, with both engines not operating, the RAT automatically provides hydraulic pressure and electrical power. Nevertheless you have to perform an emergency gear extension....if you want to extend the gear...

 

Edited August 18, 20196 yr by FDEdev

Dropping the gear to land in tilled soil would have been a huge and possibly tragic mistake.

6 hours ago, FDEdev said:

That's incorrect since the RAT automatically drops down and provides hydraulic pressure and electrical power.

There's no abnormal law. With the gear up you are in alternate law (with the gear down in direct law).

Depending on the failure, high angle of attack protection might be lost, but not necessarily.

Rat only powers the blue system. Nowhere in the dual engine failure checklist does it say to turn on the yellow electric pump either. So I am not sure how the flight controls would stay in normal law. Also it also has you pushing the emer elec pwr manual on, early on. So if you’re already ensuring that you are configured for ac buses being out, how could you still be in normal law? As for the apu, the checklist will finally get to that way down in step 11. Once it is up, you will get electrical back, but will the aircraft return to normal law? With green and yellow hyd still off? Once you drop into alternate, is it even possible to return to normal law in flight?

10 minutes ago, FDEdev said:

Again, with both engines not operating, the RAT automatically provides hydraulic pressure and electrical power. Nevertheless you have to perform an emergency gear extension....if you want to extend the gear...

 

The rat only provides blue. The gear is on green and nowhere does the checklist for dual engine failure have you turning the yellow pump on. And the only electrical that the rat can provide is ac ess and dc ess. Emergency extension is the only way.

Edited August 18, 20196 yr by KevinAu

14 minutes ago, KevinAu said:

1. I am not sure how the flight controls would stay in normal law.

2. Also it also has you pushing the emer elec pwr manual on, early on. So if you’re already ensuring that you are configured for ac buses being out, how could you still be in normal law?

3.Once you drop into alternate, is it even possible to return to normal law in flight?

1. You aren't.  

2. You push the emer elec pwr switch not to be configured, it's just a backup if the automatic switching didn't work.

3. No. 

31 minutes ago, 188AHC said:

Dropping the gear to land in tilled soil would have been a huge and possibly tragic mistake.

That's one of the problems with emergency procedures and checklists. Everyone insists that you follow it exactly and on the other hand you are expected to deviate from the procedure if necessary.

Sometimes you find out that the emergency checklist is erroneous, ambigous or it's not even applicable in your situation.

Lots of decisions and pressure during an actual emergency!!! 

Edited August 18, 20196 yr by FDEdev

8 minutes ago, FDEdev said:

1. You aren't.  

2. You push the emer elec pwr switch not to be configured, it's just a backup if the automatic switching didn't work.

3. No. 

1. Then you won’t have alpha prot. And you can’t just rely on the fbw to maintain alpha max for you. You will stall the plane if you just hold the stick back.

2. Hence the word ‘ensuring’.

3. Right.

32 minutes ago, KevinAu said:

And you can’t just rely on the fbw to maintain alpha max for you. You will stall the plane if you just hold the stick back.

You don't know. That's why I thought was funny when a certain company said that they would design a 100% accurate A320 sim for FSX/P3D.

Even on a Level-D sim, selecting e.g. a certain failure combination results in a different outcome each and every time! 

If everything is working the A320 is a nice office, but in the multiple failure and failure handling case it can be a real nightmare. 

Not only once the guys at Airbus were scratching their heads when we confronted them with certain failures and their response was almost every time; we don't know, we never heard of this problem/failure.

Don't understand why you asked the third question since you apparently know the answer?

Edited August 18, 20196 yr by FDEdev

12 hours ago, KevinAu said:

That would not be the case since if you suddenly lost both engines, you would have also suddenly lost electrical power. So you will be in electrical emergency configuration which means you’ve dropped out of normal law. In abnormal law, alpha prot is not available. The flight controls will not maintain alpha max if you hold the stick back. You will stall the plane if you do that.

I should clarify that when I said 'this' incident I was saying that in the context of the quoted AF296 incident, where both engines were running (and in Sully's case they started the APU which kept them in normal law, or at least an alpha-protected mode as the final report made clear).

 

30 minutes ago, FDEdev said:

Don't understand why you asked the third question since you apparently know the answer?

No, I don’t know for sure. You seemed to disagree with me that alpha max would not be available after a dual engine failure. If I was wrong about that, then it would mean that normal law can come back after dropping out to alternate law in flight.

3 minutes ago, skelsey said:

I should clarify that when I said 'this' incident I was saying that in the context of the quoted AF296 incident, where both engines were running (and in Sully's case they started the APU which kept them in normal law, or at least an alpha-protected mode as the final report made clear).

 

They would have to have been in alternate law with reduced protection. The fbw would provide a nose down bias at low speed, but it can be overidden by the pilot.

If the FBW introduces a nose down moment, do you know for sure that you can stall the A320 nevertheless? And why should any sane pilot even try to override the aircraft and deliberately stall it?

Btw, you can easily fully stall an A320 in normal law (at least in a level-d sim) 😉 

Well, that will have to depend on how vigorously you abuse the controls, one would suppose. I don’t know why a sane pilot would. But I bet a confused pilot can.