Boeing 757 Autoland Question

[Orion Man]

Can anyone help me with a query ?

Conducting a Cat 3B No Decision Height Autoland and passed RVRs prior to the outer marker of 200m/150m/150m. I have Cat 3A reversion.

The Tower then passes 125m/125m/125m after the outer marker and shortly afterwards the ASA then downgrades to LAND2. Do I have to go around as I no longer have Cat 3A minima or can I continue to my Cat 3A decision height ?

Thanks.

[FlightPathOBN]

you have visual?

[Orion Man]

Not yet. I was just wondering the legality that's all. Am I correct in thinking anything passed by the tower after the outer marker is irrelevant and at DH if I can see 3 lights I can land ?

Just having a brain fart on LVPs...

[172_driver]

I believe these are the paragraphs you are looking for:

(a) The commander or the pilot to whom conduct of the flight has been delegated may commence an instrument approach regardless of the reported RVR/Visibility but the approach shall not be continued beyond the outer marker, or equivalent position, if the reported RVR/visibility is less than the applicable minima (see OPS 1.192).

(c) If, after passing the outer marker or equivalent position in accordance with (a) above, the reported RVR/visibility falls below the applicable minimum, the approach may be continued to DA/H or MDA/H.

Ref: EU-OPS 1.405 (c)

[Orion Man]

Thanks. I guess that means I can continue to DH then. LVPs are very confusing sometimes and unnecessarily so. The tower shouldn't bother muddying the waters after the OM/1,000ft IMHO.

[Bealzebub]

Conducting a Cat 3B No Decision Height Autoland and passed RVRs prior to the outer marker of 200m/150m/150m. I have Cat 3A reversion.

The Tower then passes 125m/125m/125m after the outer marker and shortly afterwards the ASA then downgrades to LAND2. Do I have to go around as I no longer have Cat 3A minima or can I continue to my Cat 3A decision height ?

Two seperate issues here:

The first is the controlling RVR requirement. Provided that is equal to, or better than the specified minima for the plannned approach, at the outer marker (or equivalent position) the approach may be be continued to the applicable Decision height, even if the RVR subsequently reduces below the previous governing minima.

However the second part of your question concerns a technical degradation in the autopilot system. Once past the outer marker (or equivalent position) a change from "land 3" to "land 2" (above 200 ft) requires that the Cat 2 minimum height becomes the governing factor. The visibility (although not the visual requirements) is irrelevant.

To answer your question. The change in autoland status, once past the OM (EQV position) has no mandatory effect on the continuance of the approach, however the change in autoland technical status (above 200ft) does require the application of the new decision height requirement. In this situation you cannot continue to your Cat 3A decision height (if above 200ft) but you do not need to Go around, as you can continue to the now governing Cat 2 decision height.

These rules are slightly different in the USA, whereby the approach (post OM/FAF) can only be continued to the Alert height if the controlling RVR's drop below minima.

[Daysleeper]

For a long time a UK operator's SOP, following an ASA change, was to disconnect the autopilot and fly a manual go-around. (Unless fully visual in which case a manual visual approach could be continued.)

Something to do with a rogue box somewhere in the fleet.


The point I am making is... it depends what YOUR ops manual says.

[Birdy767]

If before passing the Outer Marker or equivalent position the RVR is 200 meters then there is a CAT IIIA reversion.

E.g.: If the ASA change from LAND 3 to LAND 2 after passing the Outer Marker or equivalent position and RVR dropped below 200 meters you can still continue the approach down to the CAT IIIA minima.

[Orion Man]

Thanks guys. LAND 2 = Cat 3A on the 757 ASA Bealzebub just to add a bit more confusion !

So in essence, as long as I have the TDZ RVR at the outer marker or equivalent position for a reversion category any reduction in RVR after the marker is irrelevant and I can continue to the reversion category DH.

[nitpicker330]

It depends on your company ops manual.

Our states:- Equipment deterioration.

If an Aircraft or Airport systems failure necessitates a reversion to a degraded approach Catagory then the approach may not commence ( ie descend below 1000' AAL ) or continue, if already below 1000' AAL unless the reported RVR readings are at or above the minima for the degraded approach Catagory.

So...... Downgrade from Land 3 to Land 2 then you MUST Go Around if the RVR's are not at or above Cat 3A.

That's our policy anyway.

[deltahotel]

The last RVR passed before the approach ban point (1000') dictates whether you have reversion or not - carry on down!!

[BOAC]

Quite a few folk here need to look carefully at post #10, particularly NP's opening line, before bandying around "It's always ok to continue" "JarOPs/EUOps etc etc " "Irrelevant"

It depends on your company ops manual.

It may be so for your company, but not for all.

[Bealzebub]

DH 50 Feet or Less

•The first four Automatic Landing limitations must be observed.
•All three autopilots must be engaged and the autoland status annunciators must show LAND 3 at and below 600 feet.
•The autopilot must be coupled to an ILS which conforms to the requirements of ECAC Document 17 Category III operations.

A change from Land 3 to land 2 indicates a single failure in the autopilot system.

Thanks guys. LAND 2 = Cat 3A on the 757 ASA Bealzebub just to add a bit more confusion !

Unless your Cat 3A minima is above 50ft, I am curious how you bypass this AFM limitation.

[deltahotel]

You're quite right - it will vary with the company. Mine says for ".....DH below 50' etc etc", so reversion ok to 50/200 if ASA goes to Land2.

[Mansfield]

It is indeed important to consider that different operators will approach this in different ways. One major US operator (at one time, anyway) required a missed approach if the RVR dropped below the published mins AFTER passing the marker, but only in the case of a fail-operational approach. This was operator specific; there is no FAA requirement to do so so long as the final approach point has been reached.

As far as the 757 is concerned, there is no manufacturer-specified relationship between LAND 2, LAND 3 and the minimums being used, nor is there any AFM limitation that I am aware of. The only AFM limitation states that if an autoland is required, LAND 2 or LAND 3 (as applicable) must be annunciated by 600 feet AGL.

The FAA requires that LAND 3 (fail-operational) be annunciated for approaches using any alert height or using a decision height of less than 50 feet. For CAT III approaches using a DH of 50 feet or greater, a minimum configuration of LAND 2 (fail-passive) is specified.

FAA AC 120-28D actually stipulates that, if the operator wants the ability to continue the approach following a degradation from LAND 3 to LAND 2, procedures for changing the minima from an alert height to a decision height, etc., must be specified in the operator's manuals. Most US operators interpret this to mean that a miss is required following a degradation simply because the company has no procedures specified for how to change the briefing/approach setup at that point in time.