View Full Version : CATIII operations. Go around below DH.

31st Oct 2009, 10:21
Hello everybody.

I'm an avionics test engineer on Antonov Design Bureau.

We've just completed the flight tests of CAT3A capability on our new regional jet An-148. It's our first CAT3 certification. Now we on the final stage of certification progress.

The question is:
"What is mandatory or the best way to do in case of autoland WARNING below decision height (DH = 50 ft)? We still have strong discussion of the subject with our test pilots. My opininon is GO AROUND, because CATIII operations require AUTOLAND. My colleagues state they can make manual landing after loss of autoland"

Thanks for your cooperation.

31st Oct 2009, 11:03
I believe if the visual reference is enough to make a safe landing than land otherwise make a go-around.

Hopefully this help a little bit

31st Oct 2009, 11:11
AF: Your question is far too technical for an open forum like this - it may yield answers not professional enough. The design team should look for certification specifications in appropriate documents such as FAR part 25 or/and EASA CS-25 ... which I am sure they do.

My last type specific LVO training was done by an ex-SAS examiner inhouse at Toulouse Airbus training center on a CAT IIIB aircraft. The advised course of action for autoland problem below minima was to DECIDE. If the real situation provides enough visual cues, it is entirely possible for the captain to land; and it is legal. If the captain does not see (s)he will go around and everybody understands that the gear will touch down during the manoeuvre. Both options are available. The key point is the term enough visual cues.

Take care,
FD (the un-real)

PS: As I proposed, my contribution may yield answers not professional enough.

31st Oct 2009, 11:55
Thanks a lot for you answer. What we have, that's only requirements, definitions and yours (I mean - world wide) professional experience. As ICAO docs state:

"Cat I and II ILS procedures differ from those of Cat IIIa in one important
respect. They require that the crew visually spot the approach lights — and, eventually, other runway environment cues — in order to safely continue to a landing by visual reference alone. In other words, the landing pilot must be able to properly judge the flare point, make the landing, and execute the rollout visually.

Cat IIIa approaches, on the other hand, merely require that the pilot establish sufficient visual reference with the touchdown zone lights to ensure that landing is occurring in the touchdown zone. The pilot may never even see the approach lights. Visual reference may be such that the pilot is unable to properly judge the flare point or manually control the aircraft during the initial rollout. The autopilot will normally execute the flare, landing, and rollout down to taxi speed."

Of course, I mean the only CATIIIA real visual conditions. It's clear, if you land in good weather you can make the decision - to land or to go around.

31st Oct 2009, 12:15
A_F - if the 'autoland warning' means the a/c is unable to complete an A/P landing, then in all the operators I have been with (737 all types) it is a mandatory g/a. The danger is that although there may be some visual clues at failure, they can rapidly disappear meaning that the flare and t/down could be endangered. I guess that if, in the unlikely event that it is CatIII for cloudbase and not visibility, you 'broke cloud' at 50'(/DH) and saw the whole runway you might be justified in going against the QRH (g/a) but I suspect there will a 'chat' in your manager's office!

31st Oct 2009, 12:34
all post about CATII IIIa Cat IIIB have a good explain and is legal to land by manual landing with visual cues (some depend of the company policy)but don't forget about if Visibility became below minima announce by ATC and any approach that you intend to land even if you have visual cues (autoland and manual land) landing is Ilegal.

31st Oct 2009, 13:06
• CAT III Operations
In CAT III operations with DH, the condition required at DH is that there should be visual references which confirm that the aircraft is over the touchdown zone. Go-around is mandatory if the visual references do not confirm this.

(Appendix 1 to EU-OPS 1.430)
- For Category IIIA operations, and for Category IIIB operations with failpassive flight control systems, a pilot may not continue an approach below the decision height unless a visual reference containing a segment of at least 3 consecutive lights being the centerline of the approach lights, or touchdown zone lights, or runway centerline lights, or runway edge lights, or a combination of these is attained and can be maintained.

You can land A.F. but it's a tough call. :ok:

31st Oct 2009, 13:32
Assuming that the design – certification standard of the autoflight system meets the requirements in CS AWO 300 and CS25 (AC 29 / FAR25), then the operating requirements (EU-OPS, FAR121) generally determine both the minimum RVR and the land/GA options for the crew.
Cat 3A does not necessarily require autoland; see CS-AWO 321.
For 50 ft DH (Cat3A) in RVRs greater than 200m (may vary by aircraft type), where the crew have and can maintain the required visual references and the aircraft is on a stable flight path, etc, etc, then the crew can continue to land.
However, a manufacturer/regulator can impose an operating limit requiring a GA if the aircraft handling / workload / flight deck view / system characteristics etc for continued landing warrants it.

One difference to the above, particularly in Europe, is if the aircraft/autoflight system is certificated as ‘highly reliable fail passive’ enabling reduced RVR operations ~ 150m, then a mandatory GA would probably be required.

EASA Certification Specifications Agency Measures | Certification specifications (http://easa.europa.eu/ws_prod/g/rg_certspecs.php)

31st Oct 2009, 13:32
Would be interesting to know if you can continue manually in HUD manual CAT III approved 737s in case of an autopilot failure.

In fail operational ones you have to check if above or below 200ft RA, the system and failure logic changes at alert height. For example the NO AUTOLAND message is inhibited, same as NO LAND 3 or LAND 2, and autoland is assured below 200ft, above 200ft it's a mandatory go-around.

In fail passive ones it is a mandatory go-around for all failures except AT disengagement, manual thrust operation is allowed in that case. However the relevant table has a note that manual landings are permitted "If suitable visual reference is established", however it fails to define what a suitable visual reference is.

However it further states for fail passive operation:

• For operations to actual RVR values less than 300m, a go-around is assumed in the event of an autopilot failure at or below DH. This means that a go-around is the normal action.
• There may be circumstances where the safest action is to continue the landing. Such circumstances include the height at which the failure occurs, the actual Visual references, and other malfunctions. This would typically apply to the late stages of the flare.
• It is not forbidden to continue the approach and complete the landing when the Commander or the pilot to whom the conduct of the flight has been delegated, determines that this is the safest course of action.

Autopilot failures are not considered for fail operational planes below 200ft as the system should be able to cope with all failures at that point, besides there is no DH anymore.

31st Oct 2009, 21:26
The visual cues requirements at DH in CAT III are meant for normal operation, I assume.
The thing is that below CAT II minima it is considered that there are not enough visual references to make a safe flare and landing, as you point out.

If there is an autoland warning, the airplane will not land, nor do an automatic roll out, so if it occurs below DH (with the required visual cues, of course, otherwise we would be going around already) it is captain's decision. If he assesses that he can flare, touch down and roll out with the available visual references he can land. This can only happen (in my opinion) if the actual visibility is higher than expected

Probably the most sensible thing to do is to go around expecting a bounce on the runway unless the he can clearly see that a landing is safe.

Besides, in a such an approach after a long haul flight, jet lag, fatigue, etc... our ability to correctly perceive the runway with just a few lights in the fog can be impaired. If the warning is due to a deviation from LOC or G/S during a landing with crosswind, Can we really see how the runway is with respect to the airplane with just three or four lights in sight, correct the flight path and land?

31st Oct 2009, 23:46
If there is an autoland warning, the airplane will not land, nor do an automatic roll out, so if it occurs below DH (with the required visual cues, of course, otherwise we would be going around already) it is captain's decision

On the L1011 type, with fail/operational performance, the statement above is not factual.
The airplane will autoland...just not as smoothly as you might expect under normal circumstances.

TriStar...in a class of its own...and very very good, even under adverse circumstances.
I kid you not.:ok:

1st Nov 2009, 01:24
If you have planned for an autoland, the safest course of action would be to execute a go around.

1st Nov 2009, 06:42
Thanks to all for professional answers.

Yes, as was pointed out, CS-AWO 321 really stands, that you can land without autoland. But in that case you have to demonstrate enough manual landings in visual conditions, that (believe me) is real challenge for certification without HUD.

And the last question.
What about flight manuals? In the most of them only one recomendation is in real visual conditions:

Boeing 777:
"Approaches conducted under Category II/III procedures require an autoland. In
cases of a failure that would require the aircraft to be manually flown prior to
touchdown, a missed approach would normally be the only safe course of action
(even if visual contact has been established with the touchdown zone)".

"In (real) low visibility ops and BELOW the DH - Go Around required if:
- AUTOLAND warning light
- N/W steering failed (CAT 3). CAT 2 manual rollout control with rudder
- AP off at touchdown (CAT 3) CAT 2 Manual rollout control with rudder
and N/W steering
- no FLARE indication on PFD at 30’ (CAT 3), CAT 2 manual flare and

Any of professional pilots of this forum, who caught LAND warning in real life, follow the instructions without thought, or try to assess the situation and land manually?

1st Nov 2009, 08:08
I think one of the main lessons for the pilot in Low Vis situations is the decision making at DH or below.

In my opinion it is at this stage when if the pilot feels he has adequate visual cues and any of the malfunctions happen then it is better to land. (A330).

There have been trainees who "forgot" to flare and the landing gear can take the resultant rate of descent comfortably.

Each pilot machine combine has a decision making process of its own.

It is a rare situation and very few may have actually had this in real life. It would be better if the same is practised repeatedly in the simulator and analysed.

1st Nov 2009, 09:03
Congratulations of reaching a milestone of the AN148 development! It's good to see some fine aeroplanes coming for the future.

Microburst2002's reply has a lot of impact. In true Cat3a conditions, having taken over manually and completing a touchdown, possibly in a 15kt crosswind, can you see enough lights to safely control the aircraft manually? It is a difficult call, but my thinking is anything that restricts capability at that stage of an AWOPs approach is an indication something is wrong with the aircraft, and that is not the time to be at a height of 15 metres in 200 metres visibility suddenly trying to fly the aeroplane! My feeling is 'go-around', but we have to remember in the real world, we have limited fuel available to us, the traffic congestion and reduced flow rate will make us reluctant to go around, and we would probably all grab the chance to get it on the ground!

Our official 737 AWOPs procedures are: for an autopilot disconnect below DH, even if visual- go around. How much diagnosis at that stage can you carry out, in an instant? You are likely to hit the ground and bounce anyway, so all attention should be on flying, not technical things apart from monitoring correct operation of Flare mode and Throttle retard.There have been trainees who "forgot" to flare and the landing gear can take the resultant rate of descent comfortably.
Disagree! 'Forget to flare' and you are looking at a 700+fpm ROD. It doesn't take much more than that to put the gear up through the wing! Have we forgotten the MacDonnell Douglas DC9 test pilot video of the rear fuselage breaking off on a hard touchdown? Make no flare at all and you may well have a problem!

1st Nov 2009, 09:04
GA below CAT IIIa is something we have to train every 6 months in the simulator, be it due to blocked runway, alignment with the runway edge instead of center or any other failure. Usually an AT failure is thrown in and it is expected that we continue with manual thrust.

For CAT IIIb there is no GA below DH as there is no DH for us, just a mandatory GA whenever the RVR drops below 75m. Since we exchange the old fail passive 737s at the moment rapidly with the fail operational ones CAT IIIa and DH will be a thing of the past soon.

1st Nov 2009, 10:05
It's nice to hear that about AN148, Rainboe. Thanks. We just try to catch by the tail all of this Boeing-Airbus-Embraer 's company. And I'm sure we'll squeeze our swallow in this market.:ok:

1st Nov 2009, 15:44

Please read the statement in correct context.... if one has been a trainer then he knows of the experience ... by the way do you know the ROD limits of your aircraft??? Please do not generalise the Boeing principles to the Airbus you are bound to come to incorrect solutions and spread a lot of misinformation.

.... how many times has one landed in actual Cat3B conditions and had a failure... I don't know of any. Neverthless one must prepare... nobody can tell the captain what to do at that stage.. it is his judgement and skill level. That is why one must prepare in the simulator

1st Nov 2009, 15:47
Go around is mandatory...

1st Nov 2009, 20:49
I don't want to get into an argument about a side issue, but you did say
There have been trainees who "forgot" to flare and the landing gear can take the resultant rate of descent comfortably.
Take a look at YouTube - DC 9 80 Hard Landing (http://www.youtube.com/watch?v=QIsbSz03WdU)
Manufacturers don't publish ROD limits for landing- it depends on too many other factors like weight, landing on one leg first etc. But a straightforward no flare landing will put most aeroplanes in jeopardy.

1st Nov 2009, 22:14

I'm sorry if I missed someone making this point: under JAR a manual landing is not permitted with RVR below 300m.

1st Nov 2009, 23:02
Under which JAR? JAR-FCL? Doesn't really apply here. JAR-OPS? Replaced by EU-OPS. However both allow manual landings with less than 300m RVR under certain circumstances. For example all those HUD equipped CAT IIIa approved airplanes with correctly trained crews may land with less than 300m RVR as normal operation.

However the question was a somewhat non-normal case, if a go-around below DH is mandatory for CAT IIIa operation. And it seems the answers are somewhat split on that. Some operators do allow it (even under EU-OPS rules), others do not.

Personally i would be very interested how those operators that have aircraft with both autoland capability and the ability to do manual CAT IIIa approaches and landings (for example 737s with HUD) cover that special case.

2nd Nov 2009, 09:47
RJ FCOM Abnormal and Emergency Checklist

Response to AP Disengagement on CAT2 or CAT3 Approach

Below DH with RVR less than 300m

With crosswind 10kts or less, a go around should be flown

With crosswind greater than 10kt, a go around must be flown

2nd Nov 2009, 09:48
I have that video and also show it to my trainees...

But as I recall the video was exactly that .... a training video with the aircraft flown by a test pilot. It was not an unintentional hard landing.

The hard landing limits is 2.6 G if converted this works out to roughly 7 to 800 feet/min. Calculation in relation to DFDR read outs.

Every company has its own view on GAs in low vis situations and the governing factor is safety and one cannot generalise. That is why the simulator training.

2nd Nov 2009, 13:38
737 Operator - Cat IIIa

BELOW DH - You may continue IF you consider you have enough visual reference to do so, no RVR limits...

2nd Nov 2009, 13:40
Considering that every second you accelerate by the value of gravity 9.81 m/s/s 2.6G is a huge figure, 1G is 588.6 Meters per minute :}

2nd Nov 2009, 13:42
Greeting, at that stage the visual reference is that the Autoland is going to take place on the ruway, so we need to see threshold or Touch Down Zone

2nd Nov 2009, 15:03
So, if the actual visibility is CAT 3 it is considered that you cannot have sufficient visual clues so you must go around with a warning below DH, according to JAR OPS?

the problem is... How do you know what the visibility exactly is?
(Please don't make me count center line lights in that moment...)

Therefore, unless it is specifically forbidden to go around with a warning below DH, wether in SOPs or in JAR or wherever, it remains a Captain's decision to continue or go around depending on his assessing the visual cues as sufficient or not.
If conditions are actual CAT3, I think we won't have sufficent visual cues for a flare and landing. And many times we won't even know why the autoland is not reliable so we don't know if we are over the threshold or what. If conditions happen to be better, we can see well and land.

However, if warning is due the LOC transmitter failure, visual cues might happen to be sufficient to flare and land on the TDZ, but not sufficient for the subsequent roll out. But this could also happen during the roll out itself after a non event autoland!

I have come to the conclusion that I don't like CAT III

2nd Nov 2009, 15:20
Below Alert height which is 200 ft on the type, (tried on the sim) Loc failure didnot bother the system, beeing on Inertial, the aircraft continued straight, flared and rolled out.

2nd Nov 2009, 15:59
Wasn't the MD80 tail snap landing a flappless approach, which would result in a much higher rate of descent than on a CATIII approach.

2nd Nov 2009, 16:06
the problem is... How do you know what the visibility exactly is?
You can only go on the latest RVR or the last RVR given to you before reaching the approach ban point at 1000'AAL.

In genuine CAT3a conditions, the rule book says any problem after Decision Ht: GO AROUND! Whether you would live to regret not doing so is questionable. To be trying to manually land and rollout at 200metres visibility and high speed is dodgy. What is the point of Cat 1 limits of 200'/600m if on a Cat 3 approach you can do just the same as a Cat1 manual landing (and hope you get away with it!)? The AWOPS regulations say Cat 2 and Cat 3 landings MUST be automatic. Trying to manually land in those conditions is really not for having passengers behind you!

RenardWasn't the MD80 tail snap landing a flappless approach, which would result in a much higher rate of descent than on a CATIII approach.
If that was a flapless approach, why were the flaps deployed in the landing position? 10 seconds of video- go watch it again!

Another 'no flare' landing, exacerbated by flaring late and driving the wheels in:YouTube - C130 WING SNAP (http://www.youtube.com/watch?v=prSfWsd7rtw)

Don't like it, aeroplanes don't, just don't like it!

2nd Nov 2009, 18:12
Here is what Airbus SOP says abnormal procedures for Below 1000ft and above DH (for CAT 2 or CAT 3 SINGLE) or above AH (for CAT 3 DUAL)AWO:

At 200ft RA and below Any AUTOLAND warning requires an immediate go-around. If visual references are sufficient and a manual landing is possible, the PF may decide to land manually.
• At flare height
If FLARE does not come up on FMA, a go-around must be performed.
If visual references are sufficient and a manual landing is possible, the PF may
decide to complete the landing.

Thus as shown above the decision to land is an option. It entirely depends on a individual's experience level and actual circumstances.

The AWOPS regulations say Cat 2 and Cat 3 landings MUST be automatic. Not valid for CAT II. Careful with your statements :ok:

2nd Nov 2009, 18:23
The AWOPS regulations say Cat 2 and Cat 3 landings MUST be automatic. Trying to manually land in those conditions is really not for having passengers behind you!

Correct, for your aeroplane, operated by your company, supervised by your CAA.

My first big aeroplane was ATR, it had no autoland and yet it was approved for CAT II operation. FD manual or AP coupled.

Afterwards I moved to A320. Policy was that all low vis approaches should normally end with autoland, however under CAT II it was allowed to manually save landing if autoland warning came off after passing DH. Under CAT III, conditions, go-around for autoland red light was mandatory between DH and touchdown. If mains have touched down, it was captain's decision whether to continue manually with de-rotation and roll-out or go around and once reversers have been deployed, stopping was mandatory. I find this policy quite reasonable, but I really have no idea whether every SA Airbus operator uses it or it was just us.

And just today, I've landed manually in CAT IIIA conditions, with official RVR being 200m. I had merely 58 pax and 2 stw behind me and yet I was both safe and legal. I've spotted TDZ lights at 70', so I had 20 ft to spare.

Ladies and gentlemen, it is my pleasure to introduce the new (to some) CAT IIIA approved gizmo: the HGS. (http://www.rockwellcollins.com/products/cs/br/avionics-systems/hgs/index.html)

2nd Nov 2009, 19:57
Rainboe It may benefit readers if you were to identify the references which support your statements and whether the recommendations are based on opinion or fact.

”The rule book says …”
The background to ‘European’ Cat 3 operations is given in CS AWO 300 – aircraft certification.
CS-AWO 321 specifies the equipment required for a range of operations, generally subdivided by equipment capability and the decision height.
Thus for 50 ft DH, autoland in not always necessary, but where fitted, and if the system fails below DH then a manual landing can be made in particular circumstances. Whether manual landing can or should be approved in these circumstance is debatable (original thread question) and in practice involves both aircraft and operational certification – not just pilots or engineers beliefs. Operators may impose additional, more stringent operating restrictions.

RVR limits (and other caveats) are given EU-OPS1 (E) – operational certification.
Cat 3a operations are not normally allowed below 200m, but there is an option for fail passive operations in Cat 3b – DH 50ft in 150m (Appendix 1 (Old) to OPS 1.430 table 8). Here, there is opportunity for confusion between the ‘older’ ICAO terminology and the new, rapidly developing equipment capabilities catered for in the new rules – i.e. a muddle (IMHO).

The visual references for each operation Cat 1 – Cat 3 vary. The actual visual requirements have been determined by the required piloting task e.g. Cat 1 may involve ‘significant’ lateral manoeuvres, whereas the equipment standard required for Cat3 should ensure that a minimum if any lateral manoeuvre being required. Most of these aspects were determined by research which involved manual landings in actual conditions. This is documented in “The Economic Cat 3 Programme 1975-80” RAE report TR81025, also in TR 79130 “Manual Landings in Fog”.
Thus your statement “… trying to manually land and rollout at 200metres visibility and high speed is dodgy…” should perhaps be qualified by aircraft type and landing speed. CS-AWO recognises that not all types are suitable for manual landing in the lowest visibilities.

3rd Nov 2009, 07:56
I see you point, all of you.

For me, as engineer, decision to make AUTOLAND or to GO AROUND in real vis. was clear, because according to regulations (CS-AWO and etc) we have done about 100 succefull autolands, the autopilot manufacturer have millions succesfull modelling autolands, we have enough autolands on our simulator and we have demonstrared the safe transition from automatic to manual control. But we haven't the statistic of safe manual landings in real CATIII vis conditions after transition to manual control below DH and we haven't equipped by HUD. Thats why I asked my question.

I think, it's really the subject for training by operators pilots and the subject for approval by our CAA.

3rd Nov 2009, 08:31
A.F, excited to see your new baby. It's about time for a come back of some traditional manufacturers from the East. If I may add a point, I'd leave the options open as a manufacturer and simply advise that it's all subject to approval of the relevant CAA. Pilots won't like it though. Best of luck with your plans.:ok:

4th Nov 2009, 02:39
Andew, the following may help alleviate your concerns about manual landing.
The research paper (TR81025) concludes the following:-
Manual landings were successfully demonstrated in RVR conditions lower than hitherto been thought possible. This established the feasibility of safe operations (with high success rate) in low visibilities (down to 240m and below) based on manual landings per se or as the reversionary mode of a fail passive autoland system.

There are additional caveats such as the need for 50ft DH and high accuracy autopilot guidance; these are now requirements in CS-AWO.

The research data supporting the conclusion indicates that manual landings were made in visibilities as low as 150m RVR, although the success rate based on the ability to decide before DH and then complete a landing started to reduce below 220m RVR, i.e. no land decision given, or the landing was attempted, but judged excessive workload.
Note that this data was for a manual takeover at DH; for landings simulating an autopilot failure below DH, the corresponding RVRs were lower, with 100% success rate at 200m and the lowest value 120m.

Note that the piloting task in the tests differed from that in commercial operations. During the tests the task was to detect and assess the conditions and cues as being suitable for landing, and then complete the landing – only the first and second attempts in the conditions were assessed to avoid ‘learning’.
In commercial operations the required visual references are thus already defined, and in stable (Cat 3) fog conditions within the RVR limit they should always be seen. Therefore the crew task is much less and crews will have the benefit of training. This provides commercial operations with an additional safety margin from reduced workload and RVR minima higher than the limiting condition.

One aspect which is not specifically included in the regulations is the cockpit view over the glare shield. As you may realise this is a critical parameter in determining the point of first contact, the extent of the visual scene, and maintaining the view during the flare. This is a judgement issue for the test team, which is encompassed in CS-AWO 321 (b) 1
(A) It is demonstrated that manual landings can be made without excessive workload in the visibility conditions; and
(B) The aeroplane has a low approach speed, is easily manoeuvrable and the height of the pilot's eyes above the wheels is small;

4th Nov 2009, 09:04
Are we talking about 140kt aeroplanes? A V1 reject in Cat3a conditions is frightening. As for much lower conditions, forget it- you are in significant danger of losing directional awareness unless you keep your head and use the localiser. Landing manually in Cat 3, in a 15 kt crosswind on a wet runway and 200 metres visibility, without the benefit of your usual horizon and end of runway cues.......difficult! And people question 'captain only' requirements!

4th Nov 2009, 09:28
Why only 15? the 737 (your type iirc) can do up to 20 on a wet runway and 25 on a dry one :)

Actually you can even get approval to land with down to 125m RVR if you have a LAND2 indication, 50ft RA of course but lower than usual CAT 3a RVR.

Having flown a 733 with HUD manually to the usual CAT IIIa limits all i can say is that manual landings are possible and actually quite a lot of fun, given the right equipment. However with any failure of equipment close to DH or below i would personally rather do a go around then try to sort things out in the very short time i have until landing. But there is allways a somewhat grey area, do you initiate a go-around if the rollout feature fails during high speed rollout in the fail operational 737s? Even if you have allready the reverser open? And those cases are what captains decision is there fore, that is why that position is usually better payed than the first officer who is not allowed to fly actual low vis approaches (simulated ones are fine though).

4th Nov 2009, 10:14
I'm struck by how every operator and country seems to have totally different procedures and limitations! I wasn't aware of so much variety.
Our AWOPs stop at 200m, crosswind limitation strictly 15kts, copilot flies all AWOPs approaches, Captain takes over at DH (50'). No 125m allowed at all.

I think once speedbrakes pop up, you should commit to rollout. Once reverse deploys, you must NEVER GA! As far as any problems from DH are concerned, unless you are absolutely sure of safety, a GA is advised. The problem is- there is just no time to analyse the failure. Loud clicks, warning lights and possibly horns or hooters going off, and it really is a time to GTHOOT (Get The H* Out Of There). Our Alert Height is 500', below which no diagnosis of faults is permitted, so I think technically a GA is required UNLESS you are completely satisfied a manual landing can be completed safely. But when you've been holding awaiting your turn, and the fuel is starting to look a bit sick, it's easier said than done to go around.

4th Nov 2009, 10:44
Yup interesting, although those limits can be company ones too.

However you have to distinguish between the two different low vis 737 models available. Fail operational 737s can be operated down to no DH and 75m RVR in LAND3 (in which case an automatic rollout failure becomes interesting) and 125m RVR DH 50ft in LAND 2 (to use 125m you need a special approval and training scheme in place, otherwise its 200m). They have the higher crosswind limit of 25kts for normal operation and 20 kts for one engine out autolands. Fail passive ones do operate to the normal IIIa limits of 50ft DH and 200m RVR, max 20kts crosswind. As if that isn't enough Boeing offers the installation of a head up guidance system which allows manually flown CAT IIIa approaches, in fact the 737 classic was the first airliner which had that feature available although that wasn't widely known.

I do agree on the no go around once the reversers are selected and that is as far as i know a boeing recommendation as well. However balked landings are available if you have speedbrakes up as they autostow once you move the thrust levers up again, still i do not really want to test it. With a required visual segment of one element (one single light) of the runway lighting system for CAT IIIb rollout however it becomes quite challenging to continue a highspeed rollout manually after a failure of the rollout system.

Sorry for the OT though.

Really hope to see the AN-148 flying around europe, looks like a neat plane.

4th Nov 2009, 12:55
Are we talking about 140kt aeroplanes?

It was 142 kt Vref for me, maximum is 146 @ MLM. No way in hell I'd be doing it without HGS operative.

As for autoland capable no-HGS aeroplanes, I think that following autoland failure, manual landing has great chance of success down to 300m RVR. Below that, it's safer to go-around.

But that's just my opinion.

charlies angel
4th Nov 2009, 16:38
Clandestino has it about right.
With no fancy,optional extras such as huds,enhanced vision aids etc etc under EU Awops shooting a LVP approach,if there is any failure below 1000' aal then a MANUAL landing may not be carried out in 300m rvr or less.
As usual with these things there is a great get out clause along the lines of:
" unless the Captain is ABSOLUTELY certain a safe landing can be made a GO AROUND must BE CARRIED OUT in <300m vis"
ergo land safely...."well done"
screw it up even slightly ..." dont let the door hit your ar*e on the way out":sad:

4th Nov 2009, 19:34
If I interpret Denti’s operating limits correctly (#39), then LAND 2 may be part of a fail operational system (hybrid) enabling either continued autoland or reversion to manual landing with HUD. I would be surprised to learn if pure manual landings were authorised in RVRs below 200m for system failures below DH; a GA is normally mandated after any failure. There are many interpretations of operational clearances (including interpretations made by the regulators) – not all are valid.

Where a ‘super fail passive’ system enables an operation in RVRs below 200m, normally a GA is the mandated (regulator) procedure below DH, vs manual landing above 200m. I would tend to agree with Clandestino; not on the safety aspects of ability, but of having one consistent operating procedure for all RVRs.
However, my experience with these systems is that for the very few (and rare) failures below DH in RVRs less than 200m, the vast majority of the crews continued with a manual landing (against SOPs). The reasons given were very low altitude and judgement of the safest option – such is human performance.
Also, the majority of the failures involved ‘inadvertent’ autopilot disconnects caused by the crew’s tight grip on the controls. Other failures were due to ILS transmission failure or interruption. Thus there is need for appropriate crew training and adequate guarding of the autopilot disconnect button – a design issue.

Re the crosswind limits, these are usually hard limits published in the AFM (vice the more normal advisory max demonstrated) and result from the autoland certification. What many operators (and operational regulators) overlook is that humans have not been ‘certificated’ for manual landing in high crosswinds on a wet runway in low visibility.
Manual landing in 25 kts wet can be a demanding task in clear visibility, in fog it’s distinctly challenging. This area identifies a significant weakness in the regulations which require good crew judgement to apply lesser limits to their operation. Another good example is in blowing snow where there is a visual disorienting effect in additional to poor runway friction – laterally and longitudinal.
Autoland systems do not consider these aspects; it’s up to the crew, many of whom in my experience forget to attend to the ‘side’ issues of low vis operations when using automation.

There may be similar problems with HUD operations. The research quoted earlier evaluated development versions of HUD and noted “problems with division of attention” between symbology and the outside world, and “problems of presenting lateral guidance”, which perhaps indicate that HUD crosswind operations might have a lower margin of safety than normal operations – again good crew judgement is required.

4th Nov 2009, 23:23
Correct, the cited limits for LAND2 are for a continued autoland. LAND2 is a degraded fail passive operation of the normally fail operational system. Automatic rollout and go-around capability is still provided. It is weird however that during normal (non degraded) one engine inoperative operation the system still announces LAND 3 (full fail operational system working) but only fail passive minimas may be used, this ties in with the lower crosswind limit of 20kts during one engine inoperative autolands.

Unfortunately we do not have HUDs in our current fleet so i can't really say if there is any SOP for continued manual landings in less than 200m RVR.

5th Nov 2009, 02:10
Denti: As if that isn't enough Boeing offers the installation of a head up guidance system which allows manually flown CAT IIIa approaches, in fact the 737 classic was the first airliner which had that feature available although that wasn't widely known.

Actually, the 737-200 wasn't first with Cat IIIA HUD; it was the Alaska Airlines 727-200 fleet with the Flight Dynamics HGS. The need for an expensive inertial system doubled the cost and limited the sales. Southwest went on to certify it in the 737-200.

Autoland gets you down in reduced vis; HUD lets you take off also. I don't think you'l find a pilot experienced with HUD who would prefer Autoland to HUD.