B757 autoland questions

[Fireworx]

Could somebody help me with a couple of issues I have about the B752 autoland system?

1. Crosswind autolandings.
According to a BA 757 manual, the "runway align" submode is used to "reduce crab angle in compensating for a crosswind condition during...an automatic landing."
It then says that on mode engagement, a slip will be initiated when the crab angle exceeds 5 degrees, removing the slip when ROLLOUT is engaged, and the crab angle remains.
This last bit seems to contradict what was said previous to that regarding removing the crab angle.
So if anyone could tell me what in reality the 757 actually does in a cross wind autoland, I'd be very grateful. Does the aircraft align itself with the runway before touchdown and if not, does it align after touchdown or does the pilot need to kick it straight for roll out?
Also, if the aircraft is to touch down non-aligned, what is the purpose of the slip? Is it to reduce the crab angle to an angle less likely to tear off the gear on touchdown?

2. If the aircraft needs to be manually aligned with the runway, is this the reason the BA manual rules out Cat3C landings? Or is it because a 0 RVR would make finding the gate a tad difficult?


Thanks in advance for any answers. I may yet pass my JAR exams!

[HPSOV]

Ok, well I dont know about the 757, but I do know about the 767, and I imagine that they will be fairly similar.
Given my recent sucess on this forum I'll be wrong anyway, hehe.

Ok,
Activation of runway align occurs at 500ft RA, activation is not displayed, autopilot will initiate a slip with maximum bank angle of 2 degrees when crab angle exceeds 5 degrees, wing leveling from the slip is initiated when rollout mode is engaged.
The purpose of this is to reduce the crab angle prior to an automatic landing.

Ok, so what does that mean?
At 500ft the autopilot will put in a bit of bank to help compensate for a crab angle due to crosswind. This bank is held until rollout is activated at 5ft RA. The idea being the aircraft will land wings level, but with a lesser crab angle, the theory being that the aircraft will not drift from centreline during that last 5ft.
It is then the responsibility of the AUTOPILOT to control the rudder and nosewheel steering to maintain (or regain if required) the centreline until the aircraft is brought to a complete stop, or the autopilot is disconnected.

[eeper]

I'm no expert on autolands as I've not done too many myself. Most of what HPSOV says seems to ring true with what I remember. There is NO pilot input until the autopilot is disengaged on the rollout. I would also point out that the autoland does a sickeningly good job of landing the aircraft which I often find disheartening after I have done another bone-rattler in zero wind!

As for Cat 3c ops, I was told by a trainer during my CPL days that although aircraft could land with zero RVR there was a minimum requirement of 75m RVR to taxi.