CAT III Approaches

[airgator]

After further review...

I found out despite the fact the AMP planes are capable of CAT III's, we are not allowed to do them. I have a feeling when they start putting the new engines on and finish the various other upgrades in the next couple years we will be CAT III certified.

 

[RampFreeze]

I found out despite the fact the AMP planes are capable of CAT III's, we are not allowed to do them. I have a feeling when they start putting the new engines on and finish the various other upgrades in the next couple years we will be CAT III certified.

I'd always been told that the original flight director, autopilot, et al. on the C-5 was Cat III capable. (i.e. that's why it had/has the funky ADI that spun around when in ILS approach mode and illuminated with the amber ring at mins and green circle when flare mode engaged) Even though the original system was Cat III capable MAC/AMC never wanted to pay the $$$ to maintain it fleet wide and was happy just maintaining Cat II capability. It wouldn't surprise me if they applied the same logic to the AMP, etc. project. Time will tell...

I would suspect that any aircraft designed or certified for some future, super-RNP approach would have to be pretty bulletproof. FMC software would have to monitor the GPS signal to detect jamming or tampering, and rely on the IRU's to help validate. Any issues in the critical regime of 0' to 200' = automatic go-around.

I don't think it would have to be that comic at all. It would be like any current RNP approach. If the FMS detects an unusual disparity between GPS position and other nav inputs (IRU, DME, VOR, LOC) it increases the ANP (Actual Nav Performance) circular probability of error. If this value exceeds the RNP (Required Nav Performance) value, an "UNABLE RNP" alert is issued and, just like today, regardless of where you are on the approach, you have to go around unless you see the runway. With a LAAS Cat III system, my guess is that if the box lost the correction signal from the LAAS unit for any reason (jamming or just simple failure) the same alert would be issued and a go-around would be initiated. So, I go back to my original position - I don't think LAAS is being fielded yet because of an FAA $$$/funding priority issue. I honestly don't think the security issue is that much of a concern.