Side-stick and computers
 

A320

1) I am sure that this a very stupid question for you, but I know that LVDT and RVDT's send signals of the side-stick to the ELAC computer. In normal law, flight mode, trim is available with all the protections. So where does the ELAC send the signal? Is there a trim computer or something like that?

Thanks to confirm these:

2) In alternate law, you don't have low speed protection, bank angle protection, pitch angle protection and hi speed protection

3) In alternate law you still have trim but positive trim stops at low speed and negative trim stops at high speed

4) In alternate law, the side-stick has a mech link with the ailerons.

5) In direct law, the side-stick has a mech link with ailerons and elevators.

6) During flare, you are in alternate law but bellow 100ft (with A/P) and 50ft (without A/P) you are in direct law (so mech link with ailerons and elevators)

7) A/P doesn't use "trim".

Thanks a lot! It's important for me because I have to present the FBW system in December to my class with a friend!

There is never a "mechanical" link. Just a direct relation stick movement to surface deflection.
My latest guess is you're trying to home build a simulator?!

Some things might have changed since I quit flying 320 five years ago, I'll try to answer as far as I can remember. Corrections are welcome.

1. No stupid questions. No special trim computer. ELAC sends signals to hydraulic actuators of ailerons, elevators and stabilizers

2. Correct, regarding the hard protections. There just might be speed stability left.

3. Trim stops at mechanical stops and that's all there is to it.

4 & 5. Control deflection is proportional to stick displacement but link is still electrical, the only mechanical link is between rudder pedals and rudder actuator.

6. Direct law is invoked by lowering the gear.

7. It does in pitch, just as any other A/P.

In A320 flight controls are actuated hydraulically and control signal for the actuation is from computers like ELAC, SEC, etc., (Rudder and THS can be controlled mechanically also). None of the flight control surfaces will move without hydraulics no matter what control law (normal alternate direct) the aircraft is in. The computers take inputs from side stick or AP, compute how much surface deflection is required and then give signal to the hydraulic actuator (with the help of a electro-valve) to move the control surface.

Trimming in pitch is done by the Trimmable horizontal stablizer (THS). Control signal is from ELAC or SEC or mechanical trim wheel.

Elevators and aileron do not have any mechanical linkages. Rudder and THS have but all actuation are hydraulic.

Thanks for your answers:

For 4 & 5:
Flight Control Laws | Direct Law - Description

For direct law, it is a direct link and for alternate law check this:
Flight Control Laws | Alternate Law - Description
For the ailerons, it is also a direct link with the side-sticks.

1) Do you agree? So it is still electrical but with pitch proportional to the stick?

2) But if we are in alternate law because we have lost Autotrim, will it be a direct connection or will it still be an electrical connection but with pitch (directly controling AoA)

Thanks...

There is no "direct link" between the sidesticks and the ailerons ever. The only mechanical links are between the rudders pedals and the rudder and the trim wheel to the stabilizer.

Yes, it's still electrical but it's proportional to the side-sticks. Right?

Air Transat 236: Air Transat Flight 236 - Wikipedia, the free encyclopedia
How were they able to turn? No electrical power so no ELAC, SEC, FAC. Or are there batteries in these computers which are able to store electricity?

I smell a RAT...

A RAT is able to power SEC, ELAC and FAC's????? I had always thought it was less powerful! So there are no batteries in the F-CTL, right?

You'd be amazed what the RAT can do.

Yes, I can see that Ike....
Do you confirm that computers don't have batteries? (SEC, FAC, ELAC)
I am not talking about the A330 F-CTL's, which are different.

Thanks,

If all main generators fail then the emergency generator will power ELAC 1, SEC 1 and FAC 1. When on 'batteries only' ELAC 1+2 and SEC 1 is powered. There are no dedicated batteries for FCTL computers.

Thanks for your clear answer!