A320 Pitch Control
 

Refer: DSC-27-10-20

If neither ELAC1 nor ELAC2 is available, the system shifts pitch control either to SEC1 or to SEC2, (depending on the status of the associated circuits), and to THS motor N° 2 or N° 3.

1. What are the possible status conditions of the associated Circuits
2. N° = Number? (Airbus FCOM;s keep mentioning N°) what is it ?
3. When does the system change from Pitch rate to G-Load for side stick pitch commands?

Refer: DSC-27-10-20 (Actuation of Elevators)Some manoeuvres cause the second jack to become active. Which Manoeuvres ?

1. The status conditions of circuits refers to their serviceability. Are they working? In the scenario you mention: as well as ELAC 1 and 2 not working, there could be an electrical failure of SEC2 or there could be a hydraulic failure of Green and/or Yellow hydraulics. In either case SEC2 will not be able to control one or both elevators. So SEC1 will take over, using Blue hydraulics.

Refer to DSC-27-10-20 General Architecture. In each flight control surface is a letter showing which hydraulic system operates that surface - usually there are two. Under each hydraulic letter there is a flight control computer number; ELAC2 or SEC3 for example. The arrows show where control moves to if the primary hydraulic service OR the primary flight control computer for that control surface fails. So for the left elevator, primary control is by ELAC2 using Green hydraulics. If ELAC2 or Green hydraulics fail, control moves to ELAC1 using Blue hydraulics. If both ELACs have failed, control reverts to SEC2 using Green hydraulics. If Green hydraulics are also unavailable, control reverts to SEC1 using Blue hydrualics.

2. N° is shorthand for the word 'number'. I only have the symbol for degrees on my keyboard but it should be a capital N and a small letter o, high up. Technically it should be followed by a full stop to indicate that it is an abbreviation 'N°.' but this is often omitted.

Your last question: which manoeuvres require both elevator jacks to operate? Normally one jack is operational and the partner jack on the same elevator provides a damping function. I guess that any time a faster or stronger response is required to achieve the commanded deflection, then all elevator jacks might operate together.
Jammed THS could be one such situation?

3. It's not that simple. The pitch law at lower speeds is pitch rate moderated by g-load, but it blends to pure g-load at about 210kt if I remember correctly.

Thank You Uplinker... Sorry for the delayed reply. Your explanation makes it way more clearer.