A320 FMA landing capability
 

A quick question regarding displayed landing capability, we know the capability is calculated independently by the FMGC's and displayed on the FMA.
There are issues with calculated capability with auto thrust faults, for example DC Ess bus and authothrust channel 1 failure.
But will it calculate an accurate capability with multiple failures? Or was it designed to operate with single failures?
Thanks
EGI

I imagine it's only interested in whatever the "worst" or the most "degrading" failure is. That is to say, if you have two failures that reduce you to Cat 2 and one that reduces you to Cat 1, then only that last one matters. Or if you have one that reduces you to Cat 3 Single and one that busts you down to Cat 2, again, only the last one matters.

Don't forget the unmonitored faults section in the QRH... That MAY be more limiting...

Yep, the Check Captain normally tries to catch me out every other simulator by failing the standby AI on a CATIII approach. It is not monitored but is required when you reference the QRH.

RE: failed ISIS

Would that be a reason for G/A below 1000 ft? (not in jest, seriously)

No. Once you are below 1,000 feet then you are considered to have commenced the approach. Below 1,000 ft, monitor the aircraft performance - don't get distracted looking for something which may have failed quietly. Anything Airbus deems to affect the Landing Capability will be announced by "ECAM or a local caution".

The ISIS should be considered at the planning stage i.e. before you commence the approach. Treat its failure exactly like an RVR received after you have passed the approach ban point (1,000 ft).

QRH "Flight crews are not expected to check the equipment list before approach. When an ECAM or local caution occurs, the crew should use the list to confirm the landing capability."

Thanks, I am still playing devil's advocate ... failed ISIS is a local caution, as there are (in general) no ECAM warnings for items in forward field of vision on the main instrument panel. What about the same failure at 1800 ft AAL?

PS: I wish this was in FCOM exactly how I feel about it. But it ain't. And there's MMEL for dispatch.

Before dispatch (when you consult the MML) is even more restrictive - daylight VMC conditions. Very difficult if you are planning to do LVOs.

Since the final approach technically starts at 1,000 ft agl. (i.e. You may continue down ILS towards 1,000 ft anticipating that you will complete any ECAM etc.)
e.g. We may continue the ILS down towards 1,000 ft if the reported RVRs are fluctuating up and down and occasionally below minima. We may then only continue the ILS beyond 1,000 ft provided the RVRs received were at or above minima. RVRs received after we passed 1,000 ft are for information only (crew awareness) and we may continue the ILS.

Similarly if the ISIS was noticed to have failed before the 1,000 ft point then we could only do CAT I. However we are not expected to check the ISIS below 1,000 ft.

Sometimes you have to be an airman and not just a manual reader/reciter. If the only thing that failed is the ISIS, it's not such a bad day.

G: we differ in defintions then. For here, final approach starts with GS* (simplified). And commencing approach = passing IAF.

AoG: the core essence of word airman(ship) is, unfortunately, being constantly dilluted by its overuse by the part of us who think it is better to "just fly" instead of reading the manuals, fail to comprehand what's written, or just decide to ignore the chapter and verse.

This is the one side of the coin.
If you are conducting a CATIIIb NO DH and the RVR falls below minimums, you have to go-around and ignore the approach ban. With this in mind you are not legal to land if the ISIS fails, it is a required equipment.

With same mentality, in the same scenario you get a nosewheel steering fault, below alert height. It is supposed that the landing capability is unchanged. No Autoland warning light. Food for thought.

BUT,

Thinking about failed or downgraded ground equipment, something fails below 1000ft, the approach can be continued, it is commanders discretion. Now with this in mind-set, you can ignore and land. However, it's not written. Maybe it's not your day and something happens...

I think here airmanship is the key. What are other options. Where is the weather. Other problems? How about your fuel...etc.

That's kinda what I tried to say, but, apparently, I was just contributing to the further dilution of the profession. I better get back to my manuals.