CAT I Reversion

[B737900er]

Hello,


I have a question regarding Cat I reversion. Is it determined using RVR and/or Cloud ceiling?

I did my first ever Autoland the other day in LVP's on the line (I got away with it for 6 years !). The RVR was 800/700/700 and BKN01 and the captain said there was no Cat1 Reversion?

Was he correct? I can see the theory that at 200DH you will be above the cloud but you can still go to 550m RVR.

Any help on this topic would be appreciated.

[FlyingStone]

You can decide to increase lower your LVO category, although normally any failure (unless determined to be such a threat that landing would be safer) below 1000ft would require a go-around. Depends on the company policy.

You can revert with only RVR, so from Cat II or III to I in your condition wouldn't be a problem. Assuming this was briefed, minimum preselected or changed and that company policy actually allows this.

[B737900er]

We bugged both CAT I and Cat III minima as per SOP.

I thought Cat I reversion was determined by RVR in which case we was Cat I able due to the RVR being 800m.

So the second question is, In what scenario would you use Cat1 reversion? If your going to perform an Autoland in LVP's surely cat 1 would not be option in the first place.

[FlyingStone]

Let's say weather is at Cat I minima and aircraft is fully serviceable and you brief and prepare for Cat I minima (only one AP, FO as PF, etc.). ATC says 1 nm before OM that RVR has dropped to 500m, so you have to do go-around and go for a Cat II/III approach.

Better solution is just to do a Cat II/III approach when vis/ceiling is close to Cat I minima - and if something fails during the approach, you can still continue to Cat I minima and try to get in during the same approach.

[wiggy]

The issue might be with your SOPs and who has got control at/below 1000': Are you thinking you can revert to a Manual Landing in the event of a "No Land 3"/"No Autoland" below 1000 radio?

Your SOPs might allow it but our company policy wouldn't.

[B737900er]

Cheers, that has cleared it up. I guess in most LVP approaches you still wouldnt get in on a CAT 1 Reversion, unless its right on Cat1 minima in the first place.

Wiggy- The FO flies the AC down to 50' with the captain taking over when he's visual (like most companies).
The LVP's came in force before the approach started so we conducted an Dual channel Autoland (738) the RVR was 800/700/700 and ceiling BKN01.

[Kirks gusset]

"Normally" Cat 1 reversion is due to an equipment failure and should be decided by 1000, re-briefed exec etc. There is no point in having briefed and set up for Cat3 to revert to Cat1 just because the weather conditions permit. Autolands need to be practiced. Of course if its Cat3 and below a 1000 there is a failure, normally go around, but to revert to Cat 1 makes no sense. If the met is below Cat 1 then you can't revert, simple. At DH you must have the required visual reference to land.
"If, after passing 1 000 ft above the aerodrome, the reported RVR/VIS falls below the applicable minimum, the approach may be continued to DA/H or MDA/H.
The approach may be continued below DA/H or MDA/H and the landing may be completed provided that the visual reference adequate for the type of approach operation and for the intended runway is established at the DA/H or MDA/H and is maintained"

[B737900er]

Thanks, but the question was regarding Cat1 reversion and what determines if you have it or not, i.e RVR or ceiling, not the intention to perform a CatIII then revert to cat 1 because of the weather is better.

I understand that below 1000' a G/A should be performed, but in the scenario I had, at 1000ft I could see +10km, the ceiling was BKN01.

"Of course if its Cat3 and below a 1000 there is a failure, normally go around, but to revert to Cat 1 makes no sense." Well if you have cat 1 reversion you can descend to Cat 1 DA.

[wiggy]

The FO flies the AC down to 50' with the captain taking over when he's visual (like most companies).

Thanks. I'll just chuck in our "take" on this.. In nutshell we're not allowed to fly our own approach in IMC for our own Manual landing. So...

Case 1. You have 550/125/125 and you decide on a Cat 1 approach, for a manual landing by the captain. The P2 will fly the approach down to DA, awaiting either a "Land, I have control" or a "go-around" call. All pretty straight forward.

Case 2. You have 550/125/125 but this time you decide/brief on a Cat 2/3 auto approach for captain's auto land. P2 flies it down to 1000 feet, then captain takes control with it coupled up......at 500 feet you get No Autoland/no autopilot :eek: ...you're still IMC :ooh:.....under our SOPs at least he/she can't continue to retain control and hand fly down to "decide" for his/her manual landing...and you sure as heck don't want to be throwing control back across the flight deck at that stage in the game. Hence in our SOPs, having committed to a Cat 2/3 approach to autoland there is no reversion back to Cat 1.

Not saying it's always going to work, but it makes things clear cut ...and of course if you're in to Force Majeur on a bad day it might all be handled differently.

[B737900er]

Hmmm in my outfit, the FO can land on 550m if he chooses to, The chances are a Cat III will be performed. So i guess Cat 1 reversion will be available in this scenario.

[Tom!]

Let's say weather is at Cat I minima and aircraft is fully serviceable and you brief and prepare for Cat I minima (only one AP, FO as PF, etc.). ATC says 1 nm before OM that RVR has dropped to 500m, so you have to do go-around and go for a Cat II/III approach.

Better solution is just to do a Cat II/III approach when vis/ceiling is close to Cat I minima - and if something fails during the approach, you can still continue to Cat I minima and try to get in during the same approach.

I'm assuming ATC had LVP's in use before when the weather was still cat 1 in your example, otherwise doing an autoland in marginal weather is a nono.:= Here they are quite eager to remind you runway is CAT1 only in those cases.

And even when ATC says RVR dropped to 500 but the runway is not protected you're out of luck (been there, had to hold 15 min until LVP's were up as no1). Unless of course you passed the outer marker and can have a look as u already said.
A runway doesn't suddenly become CAT3 autoland approved if the vis drops a mile before the OM without proper protections in place already

[B737900er]

I found in the UK that they safe guard it, if the believe LVPs are about to come in.

[wiggy]

At the danger of turning this into a Hamster wheel, but to avoid confusion...

Hmmm in my outfit, the FO can land on 550m if he chooses to

Just to be clear he/she can in my outfit ( if the other side of the cockpit agrees......:E), they can even perform an Autoland using Cat 1 limits, as long as it's briefed and operated as such (and all the usual caveats apply about the runway not being protected).

What our LVP SOPs are set up to avoid, by banning reversion down to Cat 1, is a sudden "who's doing what now!" if you've briefed for a Cat 2/3 and suddenly lose autoland capability below 1000 feet when (under our SOPs at least) the "landing pilot" (captain) will almost certainly have already taken control.

Hope that helps.