autoland

[Captain_BH]

hi guys

can someone explain this:

Airbus fcoms says that the glide slope by itself might be sometimes inaccurate ... or for example capturing false ILS

I have read some articles here that Autoland is always safe and accurate

1. would a false ILS or GS affect the operation of AUTOLAND ??
2. Do FDs follow the ILS beams or the installed data in the Boxes ??

Thanks

[rudderrudderrat]

Hi,

1) That's why we check the altitude passing various published points on the ILS.
2) If the mode on the flight director says LOC and GS, what do you think?

Edit having read Aterpster's expansion below:
During the autoland flare, the GS mode on the AP/FD will change to "FLARE".

[aterpster]

Captain BH:


Airbus fcoms says that the glide slope by itself might be sometimes inaccurate ... or for example capturing false ILS

I have read some articles here that Autoland is always safe and accurate

1. would a false ILS or GS affect the operation of AUTOLAND ??
2. Do FDs follow the ILS beams or the installed data in the Boxes ??


If you follow the proper profile on the IAP chart a false G/S is impossible to capture.

Autoland is always safe and accurate on CAT III ILS installations, at least when the weather is sufficiently bad that ATC protects the ILS critical areas. CAT III ILS installations must meet much more stringent requirements than CAT I installations.

Finally, during the latter states of an autoland the G/S signal is reduced by the on-board flight control computers and augmented by radar altimeter readings.

The target level of safety below Alert Height to completion of rollout is E10-7, which is the highest target level of safety used in any instrument operations.

An autoland in good weather and/or on a CAT I ILS has a much lower safety level because of perhaps inferior facility performance, lack of critical area protection, and perhaps crosswind components greater than permitted for CAT III weather conditions.