CAT3B fail passive

[Bungfai]

Can we perform CAT3B failed passive? I understand that failed passive is only for CAT3A.Anyone can explain this please. For B777 LAND 3 means failed active and LAND 2 means fail passive. I think I confuse. Thanks for your help.

[muduckace]

Trying to interperate..

Assuming the runway is obscured/fouled a "CAT3B failed passive?" would as I assume downgrade you to CAT IIIa (no rollout). Meaning get you to the threshold but not maintain RWY centerline during rollout.

The other interperation is that most A/C I have dealt with are completely capable of performing a CAT3 landing on 1 A/P. Most people assume that the other channels are active but in most if not all cases they are passive, good old example is the 27, the "B" servo only monitors tolerances with the "a" servo that allways is in command. This logic is shared by many other airframes during CAT landings, only one A/P is working, the others are monotoring for disagreements.

[FE Hoppy]

Embraer 170 Autoland 2 certification is 3b with 50?HAT and xxx rvr. don't remember the numbers but the fact is that a fail passive autoland can be certified for 3b operation.

[Henry VIII]

Can we perform CAT3B failed passive?Negative, fail passive is limited to min. 50 ft DH, so up to CAT IIIA.

[PEI_3721]

FE Hoppy, the anomaly with the Embraer (and other aircraft) results from the differences in terminology in various regulations, their slow amendment rate, and evolving technology.
In Europe, the certification of fail passive systems, as above, is limited to 50 ft (JAR-AWO), but the operating limits (RVR minima) can be less than the ICAO definitions via JAR-OPS.

IIRC the system that you describe is classified as ‘Super Fail Passive’, which was pioneered by the Avro RJ (50 ft DH, 150m RVR).

Thus, it would necessary to qualify the original question to give a meaningful answer.
I might be better to consider, in order, the aircraft system status, the certificated limits for that equipment (including an airport element), the operational limits (regulator and company), and finally what the crew qualifications are.

[Denti]

That seems to tie in with the operation of our 737s. The old ones are plain CAT IIIa and fail passive, limit is 200m RVR and 50ft DH. On the newer ones however you have fail active operation with CAT IIIB at 75m RVR and no DH, however if those are in LAND2 you still can get an approval for a reduced RVR limit of 125m RVR albeit with the usual 50ft DH.

[PEI_3721]

Denti, thanks for the info.
Re 737 operations with 125 RVR, what options does the crew have after a malfunction; and if a manual landing is permitted what is the justification?

I could / should have added to my list of considerations any specific crew procedures when operating with the reduced RVR, e.g. Avro RJ, with 50 ft and 250 RVR minima, in the event of a malfunction below DH the crew can continue for a manual landing. With 50ft, 150 RVR minima, a GA is required for any malfunction.

[Denti]

To be able to do a manual landing you need the optional HUGS in place which is not very common with airlines (although American Airlines new -800s have it). Apart from that you have to go around with any malfunction above DH but may land with a few selected malfunctions below DH. However training differs and some airlines tell you to go around with any malfunction regardless if above or below DH.

Fail Operational is easier there as below 200ft AGL the aircraft will suppress any single failure and just land, displaying it after rollout it canceled.

[Bad to the bones]

A330 : CAT III B, fail passive authorized DH 15 ft RVR 125
fail operational NO DH RVR 75

[Henry VIII]

Not to rebut, but original Airbus (not company tailored) FCOM 3.01.22, operating limitations, literally says :

CATEGORY III FAIL PASSIVE

Minimum decision height :.....................................................50 feet
At least one autopilot must be engaged in APPR mode, and CAT 3 SINGLE or CAT 3 DUAL must be displayed in the FMA.
A/THR must be used in selected or managed speed.

[Gumby]

Try this link:
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/bbada17da0d0bbd1862569ba006f64d0/$FILE/AC120-28D.pdf

It seems to cover, both, operational and passive ops.

[Henry VIII]

Gumby, those linked are State rules applicable to those who intend to fly to/from US.
And subject to obtain Ops Specs from FAA through a dedicated Washington lawyer only... :hmm:

Not manufacturer limitations.

[Bungfai]

Thanks.
I cannot excess the link you post GUMBY.How can I excess it?
Following is EURO OPs.Never seen what FAA has to say.

http://img15.imageshack.us/img15/8953/euopss.jpg

[Gumby]

Henry VIII,

The first post didn't address country and just made mention of the 777, not the Airbus family. :hmm: I guess I should have figured it was about the JAR, even though not the whole world, such as the Kingdom of Saudi Arabia, doesn't use it. I will say, it would be nice if the aviation world would come truly to common ground as far as regulation and licensing. :ugh:

Gumby

[Mansfield]

I will append a short handout that I developed when I was the program manager for Cat II/III at a recently failed airline. This document speaks only to the FAA definitions and viewpoint; however I believe you will find the concepts mostly consistent with other authorities. I can say that, as a developmental program manager and required document author, an in depth understanding of this material is remarkably elusive, even amongst the authorities. That is probably because of the use of identical terms with some different definitions between JAA, ICAO and FAA.

Most of the material below is extracted from FAA Advisory Circular 120-28D, which was referenced in a post above. A Google search will find it immediately. The material also relies on FAA Operations Specification C060, which specifies operator requirements for Cat III. The generic C060 is tailored by the operator in his program application, and yields the minima which can then be published by Jeppesen in tailored approach charts.

It is important to keep separate the aircraft certification, which relies heavily on AC 120-29A and 120-28D, and operator certification. The latter, in the States, relies heavily on AC 120-29A and 120-28D bust is specified in the Operations Specifications.

Anyway, I hope this is of some use.


United States Lower Landing Minimums Approval Demystified

Category II Operations

CAT II operations are precision approach and landing operations conducted with a DH of less than 200 feet (60 meters) but not less than 100 feet (30 meters), and a RVR of not less than 1200 feet (350 meters).

Certain foreign authorities authorize and publish CAT II approaches to minimums as low as RVR 300 meters (1000 feet). The FAA considers these approaches to require CAT III equipment and procedures.

Category III Operations

CAT III operations are separated into three separate subcategories:

• CAT IIIa
• CAT IIIb
• CAT IIIc

CAT IIIa is a precision approach and landing operation with an RVR of not less than 700 feet (200 meters) without a DH, or with a DH of less than 100 feet (30 meters), or an alert height (AH) of 100 feet (30 meters) or less.

CAT IIIb is a precision approach and landing operation with an RVR of less than 700 feet (200 meters) but not less than 150 feet (50 meters) and a DH of 50 feet (15 meters) or less, or an AH of 50 feet (15 meters) or less.

CAT IIIc is a precision approach and operation landing without a DH and without RVR limitations (zero-zero). CAT IIIc operations are not currently authorized.

Fail-Passive Operations

The term “fail-passive” means that any single failure of an airborne component will not result in a significant deviation in flight path or altitude. However, a fail-passive system is not capable of completing the approach, flare, landing and rollout in the event of a single component failure. Flight crew annunciation of such a failure is required, and a missed approach is the most likely best course of action.

Fail-Operational Operations

The term “fail-operational” means that in the event of a single failure of an airborne component, the system remains capable of completing the approach, flare, landing and rollout with the remaining components. A missed approach is not required below a specified point if such a single failure should occur.

The Use of CAT IIIA and IIIB

Fail-passive systems used to be restricted to an RVR of 700 feet, which corresponded to CAT IIIA. This is no longer true. Due to harmonization with the JAA, the FAA now permits operators to use fail-passive systems to an RVR of 600 feet. Therefore, there is no longer any correspondence between CAT IIIA and fail-passive systems. This has reduced the significance of the terminology. US runways are certified as either CAT I, CAT II or CAT III. The A and B terms are not used in the FAA runway certification. They still appear in generic Jeppesen charts.

What really matters is whether the aircraft system is fail-passive or fail-operational.

Category II and III Decision Heights

Category II approaches utilize a decision height in the same manner as a Category I approach. The visual references required at DH are intended to provide the pilot with adequate information to manually maneuver the aircraft to a normal landing.

CAT III approaches flown with fail-passive systems utilize a DH in a different manner than CAT I or CAT II approaches. Unless a HUD system is being utilized, this type of approach is always flown to an auto-landing. However, suitable redundancy is not present in the auto-flight system when it is functioning in a fail-passive capacity. Therefore, visual references are required for the pilot to verify that the auto-flight system is in fact guiding the aircraft to a safe landing.

Alert Height

Category III approaches to minimums less than RVR 600 are always conducted under the fail-operational concept. Fail-operational systems provide suitable redundancy to remove the requirement for the acquisition of visual references prior to landing. Instead, an Alert Height (AH) is specified. An Alert Height is the height above a runway, based on characteristics of the airplane and its fail operational system, above which the approach must be discontinued and a missed approach initiated if a failure has occurred in one of the redundant parts of the flight control or related aircraft systems, or if a failure has occurred in any one of the relevant ground systems.

Some authorities, however, may specify a decision height even for certain fail-operational approaches.

RVR Requirements

CAT III approaches flown using a fail-operational system and an alert height do not need visual references for the landing or the rollout. Therefore, any one of the three required transmissometers may be temporarily inoperative.

CAT III approaches flown using a fail-passive system, with either fail passive rollout guidance or no rollout guidance, require visual references for both touchdown and rollout. Therefore, a TDZ RVR, MID RVR and R/O RVR are required, with the R/O being advisory.

System Degradation

There is more to system requirements than just the number of autopilots. For example, the 757/767 will display LAND 2 when one of the three radio altimeters fails. In another case, the deferral, under the MEL, of the rudder pedal nose wheel steering will downgrade the aircraft because without it, there is no means for automatic rollout control. However, LAND 3 will still be displayed.

It is important to be familiar with all type specific requirements for fail-passive and fail-operational systems.

[Henry VIII]

Gumby
I intented the reference to the 777 in the first post as an example.
If it's a mistake please disregard my posts referred to the bus and accept my apologies.
If it's not, please accept and evaluate the Airbus scenario I posted.

If Bungfai initial question was related to the state rules, ok ! go and see the applicable state or area rules. FAA, EU-OPS or whatever.
But... you will always be limited by the manufacturer certification limits, if and when more restrictive.
Which is DH no less than 50ft when you fly 318>330 fail passive.

Regards :rolleyes:

[mudit_desai]

can u explain what is fail passive, fail active and fail operational approaches? what do we mean when we say, approach "downgrades" from cat IIIb to cat IIIa???

[muduckace]

Soon to know the 777,

A little auto land history,

Auto land had first required a single A/P with a monitoring redundant channel verifying input and output channels. It has always been a single flight control /A/P function with a second or third channel verifying the data to approve 3A or /B for a minimum dual land.

Good educated bet is that one input to the double or triple redundant system failed. Most likely ILS/MMR or R/A glitch or failure.

Bottom line is that most modern aircraft, hell even the 727 is capable of a 3A landing on one autopilot or servo in this case. All aircraft I know of (commercial) only use the other A/P channels for redundancy.

[muduckace]

CAT IIIc is a precision approach and operation landing without a DH and without RVR limitations (zero-zero). CAT IIIc operations are not currently authorized.


This is in the works, dual FLIR/HUD cockpits will be the future CAT IIIC authorization.

[Graybeard]

To jump from Fail Passive to Fail Active (Fail Op) in existing airframe types has historically meant upgrading the rudder.

The MD-80 has a fail pasive (single) rudder control. When the design engineers were looking at upgrading to Cat IIIb, they looked into a Fail Op cubed rudder control, whatever that means. It didn't fly.

The 737 series did not get Cat IIIb until they came out with the Fail Op rudder system, which coincided with change to triplex autoland like the rest of the Boeings, I believe. The Fail Op rudder also conveniently cured the hardover drama.

Think about it: what good would a Fail Passive rudder be in a Cat IIIb touchdown and rollout?

GB

[Denti]

No, still dual autopilot for the 737 fail operational. The rudder hardover was kinda solved a bit before the introduction of the fail operational system if i remember it correctly and was a different problem alltogether.

The fail operational 737 needed a rudder servo and rudder channel in the FCC which meant new FCCs, the usual fail passive ones do not have any rudder actuation by the autoflight system at all.

However if you have a fail operational one it can degrade to the pail passive mode (LAND2) and still provide rollout (which enables lower limits than usual for CAT IIIa), however that rollout mode of course is then fail passive as well.

[KUMOOZ]

Cat 3c has been around quite a while!

Pure Nostalgia!

http://i539.photobucket.com/albums/ff354/skippyscage/hs121/ba-hs1213-gawzz-lhr-19780923-136a.jpg

[ClimbSequence]

I flew 737 classics and EFIS. I remember the EFIS do not have autopilot rollout capability.
For those who fly NG's. Do the 737's NG have autopilot rollout capability?

[Denti]

No. At least not as standard equipment. You have to buy the fail operational autoflight system option and that includes automatic rollout. The fail operational autoflight system has full rudder authority during the latter stages of an dual autopilot ILS approach, rollout and automatic go around until you select another roll mode.

[lederhosen]

We did sim training on differences with the CAT 3B NG which was very interesting. The single engine autoland in particular is a neat feature which comes with the package. However the checker emphasised that as the authorisation for our airline is Cat 3A, those are our limits, despite what the individual aircraft is capable of.

[Denti]

True, you allways have to respect the limits on your AOC. JAR licences on the other hand just say IR CAT III and that allows all trained for types of CAT III, unlike the old national licences we used to have over here where it stated the allowable limits in the licence.

[lederhosen]

You are right it does indeed say Cat III. But you can definitely be trained and flying a Cat IIIB aircraft, and still be Cat IIIA limited. Incidentally the rollout feature takes a bit of getting used to. The first time I actually tried it I instinctively tried to put the aircraft back on the centreline. It was tracking straight but a little offset. The aircraft fights you if you try and correct it. Obviously the solution is to disconnect the autopilot...learning by doing!