Reversion Cat111 to 11

[Vref+10.....to 44]

question that has got me thinking....a quite rare occurence these days.

Is there anything that could happen on an airfield or, say to the ILS to have it downgraded from cat 111 to cat 11?....

just thinking, as i can't think of a reason why you revert to cat 11 from cat 111b on an approach....you would always go to 111a.
then again, if you were 111a to start with, can you ever have a reason to revert to cat 11?

it's just some of the manuals, state in the notes concerning LVP approaches, that "if you revert to Cat11...."

i drive a boeing if it is relevant.

any help, especially if from controllers/airfield staff would be appreciated.

...or am i just confused???........hope the query is not to confusing.

regards,

vref.

[davecfm56]

I'm confused... what's CAT one hundred and eleven or CAT eleven?

I only know about CAT I, II and III with its subdivisions...

ha. sorry.

failure of the standby ILS transmitter would downgrade the system from CAT III to CAT II

[Vref+10.....to 44]

thanks for the answer cfm56.......not the sarky one, the other.

Interesting. Where woiuld i find this sort of information?...........

Anyone else got any other ideas on the subject...?

Would it be true to say, that there is nothing in the aircraft (even cfm56 powered inferior ones) that would iniate a "reversion to cat 2/11/III/two (delete as necessary)

cheers

[dixi188]

Hi.
Our vintage A300-B4s are Cat IIIa with 2 autopilots, we revert to Cat II if one fails. Also some other failures can downgrade.

Hope this helps.

[rudderrudderrat]

Hi vref,

From A320 QRH - Required equipment for Cat II and CAT III:

Cat II for:
Only one Radio Altimeter but displayed on both sides,
or if no autothrust,
or only one FMA working,
or only one Nav Display Unit.

However we could do Cat IIIB approaches on TriStars with no Autothrust and most certainly with no Map Display.

[Vref+10.....to 44]

thanks guys....useful inputs....interesting about the A300 reversion.

i guess i was leaning towards the boeing with it's "ASA" display...to clarify if anything could appear to warrant a reversion to cat II/11/2/two from 111B/A....which i think for the boeing (75/76) it doesnt.....only a possible airfield downgrade could cause the above.

Hope i am correct.

rudderrat....yep, i come from a Tristar background too.....without starting a willy waggling competition, it was a different class in autolands IMHO.

thanks for all the replies.

[muduckace]

Gents, the reference was to ground equiptment. The only response was the loss of a stby ground emitting ILS transmitter. I Wonder who would be responsible to advize of the downgrade tower seems a bit last minute.

What kills me are un satisfactory III B's, if you do not request a protected runway the tower is not responsible for clearing all vehicles that could influence rollout. No runway is IIIB without it being confirmed by tower first.

[kijangnim]

You need Low Visibilty Operation in force , on the ATIS or the same statment by the controler

[Torque2]

Mud - I think post 3 asked another quetion referring to aircraft downgrading:

Would it be true to say, that there is nothing in the aircraft (even cfm56 powered inferior ones) that would iniate a "reversion to cat 2/11/III/two (delete as necessary

)

Don't know Boeing specifics.

[gatbusdriver]

With regards to the boeing ASA, you have three parts, LAND 3, LAND 2, NO AUTOLAND. LAND 3 means you are Cat 3b no dh capable. LAND 2 means you are Cat 3a capable, and NO AUTOLAND is self explanatory.

So the aircraft itself is never Cat 2 only, Cat 2 comes about due to the airfield being Cat 2

[411A]

However we could do Cat IIIB approaches on TriStars with no Autothrust and most certainly with no Map Display.

Most certainly.
The L1011 is dua/dual...the first to do so.

i come from a Tristar background too.......it was a different class in autolands IMHO.

Yup, the gold standard, to which others are compared.
Even today.

[muduckace]

CAT requirements have tightened up over the years, Boeing built allot land systems triple redundant (probably because they have allot of boxes in their aircraft that are made by them $$$). Douglas went with minimums for instance DC-10 and MD-11 2 ILS systems, the MD-10 being modded after the 3 ILS standard was in place had to rewire 3 ILS receivers to 2 loc and 2 gs antennas to be in compliance.

Thx torque 2

Yeah each aircraft has it's own list of minimum equipment to comply with the aircraft's CAT requirements.

Alot of aircraft will autoland and rollout on a single A/P and ILS. Just about all aircraft I know of only use 1 A/P active, the other 1 or 2 are just there to compare data.

[Spooky 2]

787

Interesting to note that the 787 only has two ILS receievers and while it has three autopilots they all live in the same box.

[Denti]

On the small boeing only 2 NAV (LOC/GS/GLS/VORDME) receivers are enough for CAT IIIb. Oh, and only 2 autopilots as well, but both are active and probably monitor themselves too, you can actually feel the second autopilot engaging if you guard the controls after the selftest during the approach.

[Vref+10.....to 44]

thanks for all the replies.

gatbus driver:. Yes, thats exactly how i understand it (on the 75/76)...there is nothing that can happen IN the aircraft to revert to Cat II.

As I have discovered it is only something associated with the airport that could cause cat III to become Cat II during an approach. (stby tx failure?)

Next question...should this still be called a reversion?....or should that term be left to what happens to the aircraft status internally?......am i being a little pedantic now?...it's just that lots of manuals refer to when blah blah fails then "revert" to Cat IIIa (ok with that)..... or CAT II!(hmmm)

vref.

[Mansfield]

What would preclude a CAT II landing with a NO AUTOLAND annunciation on the ASA?