A320 THS no back brake???

[flame_bringer]

Can't seem to get my head around how it works, Can anyone explain?

Thanks in advance

[glhcarl]

A320 THS no back brake???
Can't seem to get my head around how it works, Can anyone explain?

If the A320 THS has no "Back Brake" how can any one explain how it works?

Hard to explain how something that does not exist works!

[SMOC]

I think he means the THS has a "NO BACK BRAKE"

It prevents air loads on the stabilizer from back driving the system.

ie the hydraulic motors when commanded can turn the screw jack to move the stabilizer but air loads can not move the stab and turn the screwjack because the no back brake prevents back drive movement of the screwjack.

[IFixPlanes]

Out of the AMM:
THS
...
No-Back System
The THS actuator has a no-back system that has a no-back brake which is of a ratchet and pawl type. The no-back brake holds the ball screw in its last position. ...

[flame_bringer]

The AMM explanation is not very clear, I know it keeps airloads from moving the stab however I dont understand how a ratchet and pawl does this job, because otherwise the movement of the stab will be inhibited in the opposite direction with a ratchet and pawl and the jack screw will only spin clockwise, All it focuses on in the AMM is how to service it, check it for wear and what it does, It's not mentioning properly how it works.
I don't like to work on something that I don't know how it works.

[KBPsen]

Think of your ratchet hand tool. On that one you can change the drive direction via a lever. If you then installed a motor on your ratchet the movement of the motor could be used to reposition the lever allowing the motor to drive the ratchet in both directions. A return spring on the lever could then be used to lock the ratchet in the direction you desire.

That's the principle of how it works.

[IFixPlanes]

...I don't like to work on something that I don't know how it works. ...
Then either ask the question right or stop whining, switch off the FSX and read the Goodrich CMM. :ugh:

[KBPsen]

Then either ask the question right or stop whiningA perfectly clear and reasonable question was asked. Rather than having a go at flame_bringer to hide your own inadequacies you should perhaps instead just have kept quiet.

[IFixPlanes]

Reading through some of your posts here show me that you are really not in a position to judge my knowledge.
BTW: a look at the profile of flame_bringer might explain the mention of FSX. ;-)

[KBPsen]

I only hold a B1 and B2 licence, an aircrew licence, an instructor rating and an examiner approval. I am sure that does not even come close to your qualifications, to which I humbly yield.

I have however learned how to read a question and provide an answer to what was asked rather than provide an answer for what was not asked and then blame the person asking the question for my inability to RTFQ.

[flame_bringer]

Thank you all for your attempts to help.
special thanks to KBpsn for his informative reply.
I think I got it now so the ratchet and pawl are reversible, It appears from the AMM explanation that it has two cams and two pawls (each one is respective for a certain direction of rotation) and the switching between both is done by some internal gears based on the jackscrew torque, It makes sense this way.
I just could not understand the AMM explanation at first because it did not mention that the ratchet and pawl were reversible.

Thank you all once again.

[IFixPlanes]

I only hold a B1 and B2 licence, an aircrew licence, an instructor rating and an examiner approval. I am sure that does not even come close to your qualifications, to which I humbly yield. ...
At least you're capable of learning ;)