A330 v A320

[Natstrackalpha]

In the A320 there are the FACS - among other things they perform characteristic speed computation -


In the A330 - the SECs provide this function but the SECs in an A330 are secondary computers whereas in the A320 the SEC is the Spoiler and Elevator Computer.


There are, in the A330, 3 PRIMS for Normal, Alternate and Direct control laws.


I thought most Airbuses are supposed to be the same?


Given the differences - what would the PRIMS be in the A320, if the A320 had PRIMs [ which they don`t have] (that was for the Pickier members) - ? Would they be the FACs, ELACs and the SECs? I am trying to find a sameness here.


Thank you for your time. I know many of you have moved to the A330 from the A320 - and as you guys can gather; I am on page one.
--and they have stuck the RAT on the Green (330) instead of the Blue (320) well standard then?

[Goldenrivett]

I am on page one.

Try reading something like:
http://www.davi.ws/avionics/TheAvionicsHandbook_Cap_12.pdf

--and they have stuck the RAT on the Green (330) instead of the Blue (320) well standard then?
If you wanted to power all the ailerons (4) and both elevators, which system would you put the Rat on?

[Natstrackalpha]

Thank you Goldenrivett


-er, Green.

[sonicbum]

In the A330 - the SECs provide this function

Hi,

The characteristic speeds are computed by the Flight Envelope (FE) of the FMGEC.

[DozyWannabe]

I thought most Airbuses are supposed to be the same?

The end functionality is supposed to be the same. The commonality is primarily at the end-user (i.e. pilot) level, such that the majority of conversion training is fairly minimal. The implementation at low-level is likely to vary, because of the different use case specification.

Regarding the A320/A330-340 differences, have a look at my late Prof's writeup on his visit to Toulouse in 1993:

Report on visit to Airbus Industrie - 28-29th Jan. 1993 (http://www.kls2.com/cgi-bin/arcfetch?db=sci.aeronautics.airliners&id=%[email protected]%3E)

As far as why the computers are set up slightly differently, look at this table:

http://i1088.photobucket.com/albums/i331/turricaned/airbus_comp_table.png

I'm supposing that FCPC => PRIM and FCSC => SEC in the A340 nomenclature.

The PRIMs use an Intel 80386, which is a significantly more powerful piece of hardware than the Motorola 68k used in the ELAC of the A320. As I said in previous threads, for aviation applications the tendency is to use obsolete technology because the reliability has been practically proven. A move to a more powerful processor means that the main FC can shoulder a greater load and therefore a greater level of redundancy.

Regarding that, this blog post seems to confirm my theory:

Flight To Success: A320 verses A330 ... Fault Redundancy (http://tinyurl.com/psqh4vf)

The 330 is set up that each flight control computer can control ailerons, elevators, and some spoilers. All except for 1 can control the rudder. Not to forget there's a separate backup rudder control scheme, with its own generator and control computer.

The 320 can't make that claim. Additionally, on the 320, it's much easier to end up in Direct Law, and if you are in alternate law you are going to be without the autopilot…. I think in all cases, but not completely sure.

On the 330 the autopilot is often available in alternate law, and you don't automatically degrade to direct law from alternate law. The 320 almost always reverts to direct law from alternate law when the gear is lowered.