CATlll "Fail Passive" approach

[Spooky 2]

I'm looking at this statement and having trouble with the accuaracy. (B777)

If the NO LAND 3 message appears before the LAND 3 is annunciated on the PFD, it is an Advisory message. The aircrew should anticipate a LAND 2 fail passive approach and should adjust minimums accordingly. The minimums for a fail passive Category lll approach are typically set to a 50 foot Decision Height (DH) on the radio altimeter.

If anything I would imagine restting the RA upwards to say 100'?

What do make of this? Maybe I'm having a problem wrapping my head
around the CATlll "Fail Passive" concept. Seems like if you had aLAND 2 showing you would simply move up to CATll mins?

[hunterboy]

Unless I've got the wrong end of the stick here....
No LAND 3 refers to the number of autopilots...not the CAT of approach that you are attempting.
Therefore, LAND 2 means that you have 2 autopilots remaining, and can carry out a Cat 3A approach. ie 50 feet DH

[Wizofoz]

Pretty much spot on, hunterboy, though it can indicate other failures than just one Autopilot channel inop. Land 2 means the aircraft is CatIIIA (typically a 50' DH) rather than CatIIIB (Anything down to NO DH.).

No Autoland is actually a reverttion to Cat I. There is NO failure of aircraft system that causes a revertion to Cat II.

[The Range]

What does fail passive mean?

[gatbusdriver]

In simple terms

Fail operational, you have redundancy

Fail passive you don't

[Denti]

Wizofoz' explanation btw. covers the 737 as well :) Only 2 autopilots so the NO LAND 3 message just means LAND 3 is not available, nothing about the autopilots available.

[Mansfield]

A previous post I added to another thread on this may be of use:

http://www.pprune.org/tech-log/372808-cat3b-fail-passive.html#post4919960

[411A]

Of course, all this one channel failed business with triplex autoland systems was solved long ago, with a dual/dual fail operational autoflight system, developed by Collins Radio, and fitted to one quite noteworthy widebody jet transport aircraft.
TriStar....dual/dual from the beginning, forty years ago, this year.
Often admired, seldom imitated.;)

[aterpster]

With fail active a single failure, usually below 400 feet, permits continuing the approach.

As to U.S. carriers with fail active you use an Alert Height (AH), which is usually 50 feet. You don't have to see anything at AH, just make sure there are no pertinent displayed warnings.

With fail passive there is typically a 50-foot DA, which means you have to have the required visual references by 50 feet.

The two are significant differences with RVR values near minimums.

These DA or AH authorizations and limitations are handled by Ops Specs, not by the approach chart.

[forget]

411A, you need to read up on the history of triplex autoland, and it didn't happen in the US.

[aterpster]

411:
Of course, all this one channel failed business with triplex autoland systems was solved long ago, with a dual/dual fail operational autoflight system, developed by Collins Radio, and fitted to one quite noteworthy widebody jet transport aircraft.
TriStar....dual/dual from the beginning, forty years ago, this year.
Often admired, seldom imitated.

I would agree. I flew the L-1011 as a F/O when it was in service about two years. Then, back to the 727 as captain. Several years later I was an early check-out on the 767-200. Flew it for a couple of years, then back to the L-1011 as captain. I did a lot of auto-lands in both types. And, several minimum RVR landings in the L-1011.

They were both very, very good at fail-active operations and auto-landing. But, my subjective view is that although the L-1011 did not have a guidance/redundancy edge over the 767, it did have a bit more aerodynamic stability because of the direct lift control (DLC).

I understand that Lockeed when to Collins/Lear and say, "Tell us what you want in wing configuration and flight control systems to assure we qualify for fail-active CAT III (Alert Height). Collins/Lear indeed got involved and had a lot to do with DLC being added to the design, as well as the configuration of the wing.

[Otterman]

We operate according to 98% source data. The rest of our FCOM’s contain operator exemptions. In this chapter I can’t find any exemptions. From the excerpt below I can only conclude that you need to see LAND 3 for any form of CAT III approach. If you are not LAND 3 but LAND 2 the lowest limits are CAT II.

From FCOM I limitations.
CAT II Operations
• LAND 3 or LAND 2 must be annunciated.
• Prior to commencement of the approach, the EICAS messages SGL
SOURCE DISPLAYS, SGL SOURCE RAD ALT or SGL SOURCE ILS
may not be displayed.

CAT III Operations
• LAND 3 must be annunciated.
• Prior to commencement of the approach, 2 autoland status annunciators
and the autothrottle must be operative, and the EICAS messages SGL
SOURCE DISPLAYS, SGL SOURCE RAD ALT or SGL SOURCE ILS
may not be displayed.

[aterpster]

Forget:
411A, you need to read up on the history of triplex autoland, and it didn't happen in the US.

Do you have a reference for that history?

[forget]

Do you have a reference for that history?

As it's 'only' Wiki let me know which part of this you disagree with.

Autoland - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Autoland)

Maybe this. :hmm:

This led to the absurd situation for British Airways that as the launch customer for the Boeing 757 to replace the Trident, the brand new “advanced” aircraft had inferior all weather operations capability compared to the fleet being broken up for scrap. An indication of this philosophical divide is the comment from a senior Boeing Vice President that he could not understand why British Airways were so concerned about the Category 3 certification, as there were only at that time two or three suitable runways in North America on which it could be fully used. It was pointed out that British Airways had some 12 such runways on its domestic network alone, four of them at its main base at Heathrow.

[Mansfield]

Never underestimate the ability of a "vice president" to make foolishly ignorant remarks. However, I'm pretty sure the 767/757 was designed from the ground up around the CAT III capability, so I would not take this story as representative of Boeing's design philosophy.

[Spooky 2]

"No Autoland is actually a reverttion to Cat I. There is NO failure of aircraft system that causes a revertion to Cat II".



May have misunderstood your statement here but there are numerous mechanical failures within the B777 & 787 that will produce a NO LAND 3 and thus a LAND 2.

[Denti]

LAND 2 just means you cannot fly a fail operational approach, but you can fly a fail passive one which is still CAT III, albeit CAT IIIa now.

[Mansfield]

With regard to the NO AUTOLAND scenario, the FAA has approved Operations Specifications permitting a manually flown CAT II approach and landing...indeed, that was the way CAT II ops were originally conducted. Hence, a failure leading to a NO AUTOLAND annunciation could "revert" to a CAT II capability. This obviously depends on the operator's certification and procedures, training, etc.

[Spooky 2]

Thanks Guys!:ok:

[Otterman]

Ok guys,
The thread started with a question about the LAND 2 status in relation to landing minima for a Boeing 777. I quoted from our FCOM.

LAND 3 = CAT 3 (whatever version).
LAND 2 = CAT 2.

Now people are referring to NO AUTOLAND and still being CAT 2. The excerpt below from the Boeing 777 shows that with weather conditions below CAT 1 you need perform an automatic landing.

NO AUTOLAND = CAT 1.

Boeing FCOM 1 – Limitations
Automatic Landing
*The maximum glideslope angle is 3.25 degrees.
*The minimum glideslope angle is 2.5 degrees.
*Automatic landings can be made using flaps 20 or 30, with both engines operative
or one engine inoperative.
*With weather conditions below published CAT I minima, an automatic landing is
compulsory.
*Automatic landing under CAT III weather conditions is not allowed on runways
narrower than 45m in width.

If anybody has other limits in their FCOM’s for the Boeing 777 I am very interested in reading about them.

[Mansfield]

I suspect that some of that limitation is operator generated. We have to be cautious here to avoid confusion, as I do not know how your specific serial number airplanes are equipped. The only real answer lies within the Airplane Flight Manual for those serial numbers, and none of us can see that document.

That said, the generic Boeing 777 FCOM that I have, which is current through Revision No. 41, makes no reference to an autoland being required if the weather is below CAT I minimums. The glideslope language is the same, as is the automatic landings with flaps 20 or 30, etc. But there is no reference to CAT I, or, for that matter, to runway width.

The Boeing 777 FCTM, Revision 6, states on page 5.19, under Category II Operations, that "Category II approaches may be conducted using the autopilot or flight director only, with one or two engines".

It is obviously not unusual for the operator to place his own limitations in the company FCOM or FOM or whatever-your-authorities-want-you-to-call-the-manual. It is also common for the manufacturer-specified limits to be interpreted, not just by the pilot but often by the company and its training department, as universal to that type around the world, when they are actually only applicable to that set of serial numbers based on the manufactured configuration. All of this comes boiling to the surface in a matter of days when one is trying to set up a new airline flight ops department, with pilots from different previous carriers and a fleet of airplanes that everyone thought would be just like the ones at their last job...but, secretly, are not.

[Spooky 2]

The airplane (B777) is certified to fly CAT ll approaches with the flight director only. No autopilot, no autoland required. As stated you company may have additional restrictions on this.

[A321COBI]

agree with the above
I dont know what policies your company has but it should be certified to fly the route without any restrictions
I never use autopilot on short range anyway, its to boring

[aterpster]

Spooky 2:
The airplane (B777) is certified to fly CAT ll approaches with the flight director only. No autopilot, no autoland required. As stated you company may have additional restrictions on this.

What about auto-throttles?

Knowing the history of the CAT II program from its inception, auto-land was not an option for early adapters. So, it is inconceivable to me that Boeing would add an auto-land requirement for CAT II in any of its auto-land birds.

They are in the business of selling airplanes with permissive operational capabilities. OTOH, a conservative, safety conscious operator might wisely not permit CAT II unless auto-land is used.

IMHO, auto-land made CAT II safe. It was a crap-shoot when hand-flown with FD and A/T to a 100-foot DA when RVR was at, or not much above, 1200 (U.S.)

And, even auto-pilot coupled CAT II approaches with those old, clunky Sperry auto-pilots in 707s, 727, and early 737s, was a high-risk operation.

[777fly]

I have never heard of a Cat 111 fail passive approach. Is the documentation you have from Boeing or a third party?

The B777 autopilot system consists of 3 autopilots which, subject to full serviceability, will give LAND 3 system status and full autoland/rollout capability in CAT 3,( in fact, ANY) conditions. This means the following are possible: either a CAT3 NDH approach (no decision height) and RVR of 75 meters, or a CAT 3B approach to (say) 15R/125m if your company minima are more restrictive. A downgrade from LAND 3 to LAND 2 is fail operationaland will permit continued operation down to CAT 3A minima of 50R/200m, or CAT 2 minima of 100R/300m. Reversion to NO AUTOLAND is fail passive i.e CAT 1 minima and manual landing. This means a go-round in less than 550m RVR as below that RVR it has to be an autoapproach and landing on the B777.

Fail operational means that the system can downgrade but autoland is still possible to higher CAT 3 or CAT 2 minima.
Fail passive means that a major system downgrade will keep an autopilot engaged and the aircraft will not be left in a mistrimmed or unmanageable situation. Autoland capability is lost

In summary:
LAND 3 allows: CAT 3 no decision ht - 75m RVR OR CAT 3B 15R -125m RVR
LAND2 allows: CAT3A 50R -200m RVR OR CAT2 100R- 300m RVR

NO AUTOLAND allows: CAT 1 200R- 550m RVR manual landing

LAND3 downgrade->LAND 2 is fail operational
LAND2 downgrade-> NO AUTOLAND is fail passive

So, strictly speaking LAND 2 can mean CAT 3 limits ( 50R/200m)

[Denti]

Thanks for the clarification, seems boeing uses the same indication for different purposes in different models.

By the way, fail passive CAT III is the standard equipment on the 737, you can order fail operational CAT IIIb which then sports the nice LAND 3 and LAND 2 indication as the other boeing aircraft. Fail operational is then done with 2 autopilots only and LAND 2 simply means you are on fail passive status and due to fail passive operation you have to use higher minima (50ft 125m RVR instead 0/75), rollout is still available though. Single engine will usually give LAND 3 status, however due to certification only CAT IIIa minima are usable.

Reason for the 50ft minimum during fail passive operation is the ability to still successfully initiate and fly a go around with any failure down to minimum and land with visual cues below that. During fail operational you do not need that as any single failure below AH (200ft, land or go-around decision taken there) still allows a successful autoland.

LAND 3 fail operational -> 0ft/75m
LAND 2 fail passive -> 50ft/125m
NO AUTOLAND -> CAT I.

[Checkboard]

Still some confusion of the Boeing "LAND 3" and "LAND 2" terminology (meaning three autopilot and two autopilot auto-land engaged respectively), and the ILS approach certification of "CAT III" and "CAT II".

CAT I = 200' minima, hand flown raw data is OK.
CAT II = 100' minima, pilot guidance required by the regulator, (either auto-land certified autopilot or flight director), specific pilot training.
CAT III = 50' (IIIa) down to 0' (IIIb), auto-land certified autopilot required, specific pilot training.

Companies which don't want to go the expense and bother of certifying their crews for FD guided, hand flown CAT II approaches (i.e. an exercise in the simulator) simply train for auto-land CAT III, and write a requirement for CAT II approaches to be auto-land only (avoiding the requirement for the hand flown exercise).

[Denti]

LAND 3 and 2 corresponding to the number of autopilots is only correct for some boeing aircraft. The 737 and as far as i know the 787 only have two autopilots to begin with and still allow LAND 3 operation.

We would love to fly FD CAT II approaches, however the authority does not allow it because of different certification specs than in other countries.

[Spooky 2]

The 787 does have three autopilots it's just that they all live in one box. Think of them as individually partitioned channels and you will be okay with the concept.

The 787 has only two radio altimeters which is a departure from the past.

[411A]

411A, you need to read up on the history of triplex autoland, and it didn't happen in the US.

Well aware,forget...however,my remarks were directed toward a dual/dual system, and that most definitely was developed in the USA, and fitted to the L1011.
Nothing finer...even today.

[Mansfield]

Checkboard hits the nail on the head.

This is a pretty simple system that has been thoroughly convoluted by terminology. The problem lies with the relationship between the terms Category IIIA, Category IIIB, fail-passive, fail-operational, LAND 2 and LAND 3...and I'm sure the Airbus and other equivalents. Apparently no one at Boeing foresaw the human factors train wreck that was set up by placing the term LAND 2 in proximity with CAT 2. Nor did anyone at the FAA or ICAO foresee the absolutely total intuitive disconnect of a term such as "fail-passive"...although the intuitive capacities of those august organizations has been measurably elusive. Oh, well...we're stuck with these terms.

I will submit my opinion that the terms CAT IIIA and IIIB are useless in anything but a historical context. They did, at one time, represent a staged evolution of the all weather landing concept. There was, at one time, a correspondence between CAT IIIA and a fail-passive system, and CAT IIIB and a fail-operational system.

That is not true today. Fail-passive systems can be used, within certain constraints, on an approach that falls under the Category IIIB definition. All runways in the States are certificated as either CAT III, CAT II, CAT I or VFR. In the EU-OPS, Appendix 1 to OPS 1.430, paragraph e(3), contains a note which says:

In the case of a CAT III runway it may be assumed that operations with no decision height can be supported unless specifically
restricted as published in the AIP or NOTAM.

The note makes no reference to IIIA or IIIB.

The EU-OPS go on at great length, when discussing visual references, to distinguish between IIIA and IIIB operations. I would submit that you could remove these terms completely, and refer instead solely to

fail-passive operations, which by definition require a DH,
fail-operational operations with an authority-mandated DH, and
fail-operational operations with no DH.

OPS 1.430, Appendix 1, suggests a set of requirements that follow logically and which may shed more light on this issue:

(2) Decision Height. For operations in which a decision height is used, an operator must ensure that the decision
height is not lower than:

(i) The minimum decision height specified in the AFM, if stated;
(ii) The minimum height to which the precision approach aid can be used without the required visual reference; or
(iii) The decision height to which the flight crew is authorised to operate.

(3) No Decision Height Operations. Operations with no decision height may only be conducted if:

(i) The operation with no decision height is authorised in the AFM;
(ii) The approach aid and the aerodrome facilities can support operations with no decision height; and
(iii) The operator has an approval for CAT III operations with no decision height.

Notice the references to the AFM, operator approval and flight crew authorization. There are no references, in these paragraphs, to IIIA or IIIB.

From this, and the similar logic presented in the FAA Advisory Circular 120-29A and 120-28D, which covers the topic in US operations, there is a set of questions that I believe may provide a logical way of thinking these issues through during day-to-day operations:

First, what is the airplane certificated and equipped to do? This one is strongly influenced by the MEL and inflight discrepancies.

Second, what is the runway and approach system approved and currently equipped to do? This one is strongly influenced by NOTAMs.

Third, what is the company approved for?

Fourth, what are the flight crew qualifications?

The latter two questions are most likely bundled together in your ops manual, and you may not be able to distinguish which is which.

The bottom line is that company approval can be trumped by equipment deferrals and failures in either the aircraft or in the approach system. Conversely, the company approval itself may preclude utilizing the full capabilities of either the airplane or the runway. Discussion of the above four questions will make for interesting debate during training. I suspect that in many cases, you may find training staff who are also not very clear on the questions we have been debating in this thread. That is a much larger issue.

[posrategearup]

To Spooky2. You were asking why not just set Cat II mins if the airplane says "NoLand3". Cat II mins are right around 100 ft on the radio altimeter - with the approach survey, it may be slightly more or less than 100 ft - and an RVR of 1200/1600 (occasionally in Canada, 1000) ft. A Cat III Land 2, on the other hand, uses a DH of 50 ft, and allows the approach to begin with an RVR of only 600 ft. There is a very definite advantage of being able to fly a Land 2 over a Cat II.

[Spooky 2]

I don't think you understood my original statement? I'm not suggesting anyone should fly a CATll approach in Lieu of a CAT3, (LAND 2) approach. Big difference.:ok:

[captplaystation]

I am glad this thread re-emerged , if only to read 411A's post ! !


In his memory I add the description I was once given by the father (a BA L1011 TRE) of a lowly flying instructor colleague of mine circa 1981

PFM ! = pure f***ing magic, for sure, in that era , it truly was, although the good old Trident was too.
Great incentive to develop these things living on a sh1tty foggy island. Well, Paris ain't too good either, and we cannot deny Froggy achievements in that direction either ( l'aeropostale/ the Mercure etc)