julesmusician
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Foggy Landings - Attempts Or Just Divert?

Tue Nov 22, 2005 10:43 pm

Question arising from the fact that the UK has been fogged out for a lot of airports yesterday and today. BA just cancelled all their regional flights which I find amazing, I thought we were in technology now that allows foggy landings.

The question is:

If the prediction at the destination airport is for severe fog which is below minimums set for your aircraft - are you allowed to "go have a look" - I mean by that is going into the approach in case it turns out clearer than predicted or is it usual that the flight will be cancelled? Just having a look at the airports that were affected - BA cancelled the regional flights, Easyjet managed to land all their aircraft so there must be substantial different operating criteria for the aircraft - sounds like the airports are all equipped with the necessary, just the aircraft are not. I was always of the belief you could fly to the destination and then see what the current visibility is and if it doesn't work out choose a diversion.


J
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
oly720man
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RE: Foggy Landings - Attempts Or Just Divert?

Tue Nov 22, 2005 11:22 pm

Incoming aircraft will either hang around until the minima are exceeded and divert when fuel levels get low or divert straight away if the weather's too bad/ doesn't look like getting better. I don't think pilots will risk an approach on the offchance that the weather will improve by the time they get to the airport because an approach and go around is more risky than orbiting a beacon, possibly in bright blue skies above all the fog.

The RVRs are not predicted they are measured with instruments along the runway so ATC knows immediately what the touchdown/midpoint and stop end visibilities are.

Departing aircraft won't depart because if there's an emergency they may not be able to land again.

A lot of BA's regionals were on the EMB145 which may not have the same minima as other aircraft such as the A3xx and B737s of EZY.

The reason for cancellations was probably because the inbound aircraft had diverted and the logistics of getting all the outbound PAX to the other airports was not worth the effort/risk, especially given the road conditions.

Could the diverted aircraft have flown out empty to their next destination to return and possibly divert again when they came back and have even more PAX to ferry about in coaches?
wheat and dairy can screw up your brain
 
fly707
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RE: Foggy Landings - Attempts Or Just Divert?

Tue Nov 22, 2005 11:22 pm

May be pilots are not CAT III approved or the maintenance program don't include CAT III approval.
Without mistakes we will never learn
 
VuelingAirbus
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RE: Foggy Landings - Attempts Or Just Divert?

Tue Nov 22, 2005 11:29 pm

Well - i don't want to get too much into detail but landing in fog (so called CAT2/3 - Approaches) depend on many factors. The crew has to trained and have a valid endorsment in their licence and the aircraft has to be equipped. Both is costly and the smaller the airline and the smaller the type operated the less chance you have that the managment would do it. For CAT 3 you need two independent autopilots (might be replaced by a head up display) and autothrust... its just not worth for a regional airline. Plus there is another consideration. The approach spacing has to be much higher than under visual conditions (the tower cant see you and you would interfeer with the ILS signals for the traffic behind you if the spacing is to close). That means that the capacity which a runway can handle goes down a lot. Which aircraft would you divert? A 747 or a CRJ? hope that helped...

RGDS
 
PhilSquares
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RE: Foggy Landings - Attempts Or Just Divert?

Tue Nov 22, 2005 11:40 pm

Quoting Julesmusician (Thread starter):
are you allowed to "go have a look" -

Simple answer, NO! If the field is below minimums when you arrive, you either hold until it comes up, if you have enough fuel. Or, you divert to your planned alternate.

There is no "look see".
Fly fast, live slow
 
VuelingAirbus
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RE: Foggy Landings - Attempts Or Just Divert?

Tue Nov 22, 2005 11:52 pm

Quoting PhilSquares (Reply 4):
There is no "look see".

Technically i have to disagree. Under certain circumstances there is a look and see. Lets say the field reports fog patches and the RVR varies and I start a CAT 2 approach. I get constant RVR messurments but beyond the OM I can continue and "look and see" even if the RVR goes down below minima. The result would be a go around at 100 feet if I dont have visual references but in that case I did look and see. However - I am not allowed to start the approach in the first place if the conditions are reported to be below the minima applicable to the approach I intend to do....
 
Bellerophon
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 12:41 am

VuelingAirbus

...beyond the OM I can continue and "look and see" even if the RVR goes down below minima...

Yes you may, but technically the RVR cannot go down below minima after passing the OM, because any RVR given after passing the OM is advisory only, and does not affect the legality of the approach.

The last RVR received on approach before the OM is the relevant RVR for deciding whether or not you may legally continue that approach beyond the OM down to DH.

As you say in your example, if the last RVR passed to you before the OM is above your limits, you may continue down to DH, even if, once beyond the OM, further advisory RVR reports suggest the RVR has deteriorated below limits.

However, this is not a "look and see" approach. The last official RVR was above your limits, and the approach therefore is perfectly legal.

Other than in an emergency, there is no occasion when you may legally continue an approach beyond the OM, down to DH, when the relevant RVR for that approach is below your minima.


Regards

Bellerophon
 
A3204eva
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 12:58 am

Even if the rwy/aircraft were CATIII, they could not land because the RVR must be at least 75m.
"They have lady pilots......... they're not that good, but they have 'em"
 
CosmicCruiser
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 1:20 am

Quoting Oly720man (Reply 1):
Departing aircraft won't depart because if there's an emergency they may not be able to land again.

If you're legal to t/o you're flight plan will have a t/o alternate which for 3 and 4 eng. a/c must not be more than 2 hrs. away at one eng. inop cruise speed in still air.
 
CosmicCruiser
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 1:41 am

Quoting Bellerophon (Reply 6):
Yes you may, but technically the RVR cannot go down below minima after passing the OM, because any RVR given after passing the OM is advisory only, and does not affect the legality of the approach.

I must disagree at least for the U.S. FAR 121.651 (c) says that the capt. may continue the approach below MDA,DA or DH and land provided the a/c is in a position to land in the touchdown zone making a normal rate of descent AND The flight visibility is NOT LESS than the minimums for the approach procedure.
TDZ RVR is always controlling for CAT I, II and III. MID and R/O may be required and advisory only or not required at all for CAT I & II. CAT III TDZ MID and R/O are required and controlling with R/O adv.; RVR less than 600'(175m) then all 3 are controlling.

According to our ops man. even in foreign countries that allow "Look See" approachs (beginning or continuing an app. with below mins wx.) we are not allowed to do it.
 
usnseallt82
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 1:53 am

Quoting Oly720man (Reply 1):
The RVRs are not predicted they are measured with instruments along the runway so ATC knows immediately what the touchdown/midpoint and stop end visibilities are.

 checkmark  yes 

Exactly right. RVR's are instant readings from the runways that tell exactly what the visibility is. There is always the chance that things could clear up before the next RVR is posted, but the tower will always know the immediate conditions. If the RVR is calling for below mins, chances are it isn't going to improve significantly when you arrive. You can always contact ATC to get an updated reading, but if that's below mins then you're better off to divert.

Also, be aware that most airlines hold rules and regulations for these types of circumstances that are more stringent than the federal regs. You may be able to legally land in certain conditions, but it may be against your company's specific regs. This may be the difference between the EasyJet flights and BA Regional ones. Regardless, unless you are experiencing some sort of emergency on board, it is best not to test the accuracy of the RVR readings by having a 'look see.' You may be able to do it legally, but I'm pretty sure your company would have a shit fit if they knew what you were doing.

Hope this helps.  bigthumbsup 
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julesmusician
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 2:09 am

Thanks for this. It just seems strange that if the 737's etc of Easyjet can get in without problem, and BA's Emb's cannot, then that will be remembered by business travellers. Since the majority of regional work by BA to Europe appears to be buisness passengers I would argue, this is a route that BA should be investing substancially in. It only takes someone with a brain at Easyjet to publicise the fact that if you want to go regional, take them as they will get in. Some airports in the UK suffer a lot from fog. I can just see a newspaper advert from Easyjet showing BA up.

I assume that BA probably coached their pax to London as their network was so big they could get them out through their main hub.

As for the technical side of things, I assume that you would be in constant contact with air traffic and they would be updating you every minute with visibility. What I can't understand is why GPS isn't used much more in close approaches. The accuracy now is incredible down to a few metres, which is certainly enough to get in real close to see if you can see. You know the height of the runway so it should be straight forward. Maybe GPS just isn't considered good enough or stable enough. With two or three GPS units cross checking each other I reckon the accuracy would be near on 100%.

Thanks for the information so far, of great interest.

J
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
usnseallt82
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 2:23 am

Quoting Julesmusician (Reply 11):
What I can't understand is why GPS isn't used much more in close approaches.

GPS is still not considered precision approach though. It may be extremely accurate these days, but its nothing compared to the sensitivity of an ILS on short final or a PAR at a military base.
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rdwootty
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 6:13 am

I am astounded that this is still a problem.
British European Airways had a Trident land at LHR in NIL visibility and this was over 30 years ago (cant remember the date!)
 
julesmusician
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 7:34 am

Can the pilots answer - when you are doing a fog approach do you have to declare to Air Traffic what Cat you aircraft and your pilots is approved for? Or is that your own business they will just give you information...The other thing is the mix of different measurement units. On the one hand we have km and metres then on RVR are the METARS in feet?

EGSS 222220Z 35002KT 0200 R05/0250 R23/0275 FG VV/// 03/03 Q1039

Is this RVR of 250ft or 250 Metres? I assume the 0200 is general visibility in metres...

J

Below is a quote from a previous forum post about categories and landing decisions for any people who aren't aware of the different Cat landing standards...

Quoting 747Teach
Mirrodie: Some operators have been authorized to operate certain aircraft into reduced weather minimums. These carriers have a program called the Lower Landing Minimums (LLM) to keep their operations in compliance with the FAA rules. Basically, three separate functions must occur to be legal to operate in reduced weather minimums. The aircraft must have the required equipment, certified and in working order, the airport must have the required equipment, certified and in working order, and the crews must be trained and certified to fly into those conditions.
The LLM program allows operation of aircraft into very low visibility weather conditions. The factors controlling the minimum runway visual range (RVR) and decision height (DH) within which a pilot-in-command may conduct an approach and landing are based on the operational status of several aircraft systems and their components.

The catagories you are asking about are described as follows:

Category 1: An instrument approach procedure which provides for approaches to a decision height of not less than 200 feet and visibility of not less than 1/2 mile or RVR of 2400 feet (RVR of 1800 feet with operative touchdown zone and runway centerline lights).

Category 2: An instrument approach procedure which provides approaches to minimum of less than DH 200 feet/RVR 2400 feet to as low as DH 100 feet/RVR 1200 feet.

Category 3a: A precision instrument approach and landing with no decision height (DH), or DH below 100 feet, and controlling runway visual range not less than 700 feet.

Category 3b: A precision instrument approach and landing with no DH, or with a DH below 50 feet, and controlling runway visual range less than 700 feet, but not less than 150 feet.

Category 3c: A precision instrument approach and landing with no DH and no runway visual range limitation.

As you can imagine, not all operators choose to operate their aircraft into all of these conditions. The initial cost of the equipment, and the cost of maintaining that equipment, could be considerable. Many airports do not have the required equipment installed for the same reason. The cost of training and keeping aircrews current could be very high. The cost of not having all of these factors in compliance is increased diversions. In many cases, operators do not feel the additional cost outweighs the increased chance of diversions.

FAA Advisory Circular 120-28C dated 3-9-84 may be of use to you as reference. Regards,




[Edited 2005-11-22 23:43:32]

[Edited 2005-11-22 23:44:34]
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
OPNLguy
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 7:49 am

Quoting Oly720man (Reply 1):
Departing aircraft won't depart because if there's an emergency they may not be able to land again.

In the UK, there are no such things as "takeoff alternates?"
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
Pihero
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 8:00 am

Hi, Jules !

Quoting Julesmusician (Reply 14):
when you are doing a fog approach do you have to declare to Air Traffic what Cat you aircraft and your pilots is approved for?

Low visibility procedures (LVP) are broadcasted on the ATIS. It is then up to the crews to check their minima and decide whether they could attempt an autoland or hold or divert. Normally each operator has submitted their minima to the airport authorities. If found that you landed below your minima, You and your airline will be in dire trouble.

Quoting Julesmusician (Reply 14):
The other thing is the mix of different measurement units. On the one hand we have km and metres then on RVR are the METARS in feet?

As per ICAO recommendations, the visibility -or for precision approaches, the Runway Visual Range (RVR) - is given in meters.Some countries, including the USA prefer the statute mile and feet .Still according to ICAO standards, they should add SM or FT at the end of the vis data.But it is not done all the time.

Your example therefore reds as this :

EGSS:22.20Z observation :wind :350°/2knots;visibility 200meters;RVR runway O5:250 m ; RVR Runway 23 :275 m ; FOG ; ceiling unavailable ; temperature and dew point : 3°c ; QNH 1039 hp.
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julesmusician
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 8:07 am

Thanks for that, so my previous post on the RVR in feet is for the category divisions, but the actual METAR is in metres. How do you know if they are in ft or metres - is it made clear on the METAR or do you have to guess depending on where you are? (you say it is not done all the time in the US for example)

The interesting question is starting an approach - it seems you must be told that the RVR is at least to the category you are ok for before you can even turn onto finals and descend. I find that strange in that all the way down you are likely to be in fog, and as you descend the visibility may increase and allow you touchdown - however the arguments put forward about a go around in fog being much less preferable than holding is a good one.

J

[Edited 2005-11-23 00:08:16]
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
PhilSquares
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 8:20 am

Quoting VuelingAirbus (Reply 5):
Technically i have to disagree

My answer was based on the WX prior to crossing the FAF or G/S intercept altitude. Once you're inside those points, it can go to 0/0 and you can still land.

At most airlines I've been associated with, if the WX is below your minimums once you arrive, you don't have the option of a "look see" even if it's authorized in that specific location. Usually, the liability issues outweigh any possible benefits.
Fly fast, live slow
 
julesmusician
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 8:24 am

Quoting VuelingAirbus (Reply 3):
For CAT 3 you need two independent autopilots (might be replaced by a head up display) and autothrust

Autothrust same as autothrottle?
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
Pihero
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 8:34 am

Quoting PhilSquares (Reply 18):
At most airlines I've been associated with, if the WX is below your minimums once you arrive, you don't have the option of a "look see" even if it's authorized in that specific location. Usually, the liability issues outweigh any possible benefits.

I agree.Basic ICAO IFR rules.
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ShyFlyer
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 10:31 am

Quoting Usnseallt82 (Reply 12):
GPS is still not considered precision approach though. It may be extremely accurate these days...

Actually, with WAAS, GPS has the ability to meet CAT I minimums. These types of approaches are not yet in widespread use, however.

I'm surprised no one has mentioned Horizon and thier use of HUDs, or just HUDs in general. I remember reading somewhere (and I'll be darned now that I can't find it) that Horizon use of HUDs get them in an out of foggy airports when everyone else is on the ground. Can't remember the specifics though.

This link is also of some interest: Gulfstream Enhanced Vision System. Pretty cool videos too!
I lift things up and put them down.
 
411A
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 10:52 am

Not only the Trident, Rdwootty, but the Lockheed TriStar's that BEA had also had the same capability.
New is not necessarily better, it seems.
 
OPNLguy
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 11:52 am

Quoting ShyFlyer (Reply 21):
I'm surprised no one has mentioned Horizon and thier use of HUDs, or just HUDs in general. I remember reading somewhere (and I'll be darned now that I can't find it) that Horizon use of HUDs get them in an out of foggy airports when everyone else is on the ground. Can't remember the specifics though.

Me also. Now that all the 737-200s, our entire 737 fleet (-300s, -500s, and -700s, 441 in all) have HGS, and we hand-fly approaches down to CAT-IIIa (RVR700). Takeoff mins are 1/4SM RVR1600, or RVR600/600/600 (depending upon what's installed at the airport), and on SEA 16R we can depart with RVR300.
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
jspitfire
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 11:56 am

The Vancouver area has had really dense fog for the past 3 days, and I think YVR has only gone up to 1/2 SM vis a couple times. It has usually said either 1/8 or 0 SM. Because this fog was forecast, and they know that it will be there for the entire day, most flights that could not do an approach or takeoff were cancelled before they left. The float planes and Helijet have not been doing flights between downtown Victoria and Vancouver either due to the fog.

It has been a bit weird though...I do my flight training in Abbotsford, which for those that know the area, isn't too far from Vancouver. The entire Fraser Valley has been covered in Fog, but Abbotsford has remained clear every day. It works well for us if we're just flying around the airport, but we can't go anywhere else!

Jason
 
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Starlionblue
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 12:43 pm

Quoting Julesmusician (Reply 11):
What I can't understand is why GPS isn't used much more in close approaches. The accuracy now is incredible down to a few metres, which is certainly enough to get in real close to see if you can see. You know the height of the runway so it should be straight forward. Maybe GPS just isn't considered good enough or stable enough. With two or three GPS units cross checking each other I reckon the accuracy would be near on 100%.

As has been mentioned, GPS isn't really good enough yet. Systems with a combination of GPS and airport beacons are being tested, that would allow ops at zero viz.

Quoting Rdwootty (Reply 13):
I am astounded that this is still a problem.
British European Airways had a Trident land at LHR in NIL visibility and this was over 30 years ago (cant remember the date!)

LANDING in zero viz is fully feasible today. But now what? You're sitting on the runway. How exactly do you propose finding the turnoff, let alone taxiing to the gate? That's the problem.


Future systems may allow ops in zero viz, but:
- You'd have to equip EVERYONE with them. If there's a fire, the firetruck needs to find the plane, for example. This is expensive.
- There's still no agreement on a standard.
- You still wouldn't be close to the frequencies with good viz. Very few airports have so much traffic it's worth doing for the few occasions when viz is really that bad.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Bellerophon
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 5:27 pm

OPNLguy

... In the UK, there are no such things as "takeoff alternates?"...

Yes. JAR-OPS 1.295(b)

A take-off alternate must be specified, and annotated on the flight plan, if it would not be possible to return to the aerodrome of departure for weather or performance reasons.

Normal minima apply, the EFATO case must be considered, and it must be within 60 mins at the engine-out cruise speed for 2e aircraft, 120 mins for 3e/4e aircraft.


Starlionblue

...Landing in zero viz....now what?....How exactly do you propose finding the turnoff, let alone taxiing to the gate? That's the problem...

Exactly that problem arose early Sunday morning at LHR.

Various aircraft bound for Terminal 4 autolanded on 27R in Cat 3 weather. The fog then thickened considerably as they approached T4 and a few of them then reported that they were unable to locate their parking gate in the fog and had stopped to await a ground leader vehicle to guide them in.

No point in going for even lower landing minima until the ground handling difficulties have been resolved.


Regards

Bellerophon

[Edited 2005-11-23 09:29:35]
 
TheSorcerer
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 9:22 pm

A/C with HUD have lower visibility minimums don't they?

The Sorcerer
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OPNLguy
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 10:58 pm

Quoting Bellerophon (Reply 26):
Yes. JAR-OPS 1.295(b)

Good, that should put this statement to rest:

Quoting Oly720man (Reply 1):
Departing aircraft won't depart because if there's an emergency they may not be able to land again.
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
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zeke
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 11:23 pm

Quoting Julesmusician (Reply 14):
Below is a quote from a previous forum post about categories and landing decisions for any people who aren't aware of the different Cat landing standards...

They vary from country to country

Low Visibility Operations and in particular CAT II/III equipment represent a significant cost for an airline.

The higher the category, the lower the visability and cloud base for an ILS approach.

The desired level of safety is achieved through:
− Airborne equipment,
− Non-visual aids (ILS facility),
− Visual aids (runway marks, lighting systems),
− Flight crew training,
− Flight crew procedures,
− ATC procedures,
− Aircraft maintenance,
− Airfield maintenance,
− Criteria for obstacle clearance.

CAT II weather minima has been established to provide sufficient visual references at DH to permit a manual landing (or a missed approach) to be executed (it does not mean that the landing must be made manually).

CAT III OBJECTIVE
The main objective of CAT Ill operations is to provide a level of safety equivalent to other operations but in the most adverse weather conditions and associated visibility. In contrast to other operations, CAT III weather minima do not provide sufficient visual references to allow a manual landing to be made. The minima only permit the pilot to decide if the aircraft will land in the touchdown zone (basically CAT III A) and to ensure safety during rollout (basically CAT III B).

Therefore an automatic landing system is mandatory to perform Category III operations. Its reliability must be sufficient to control the aircraft to touchdown in CAT III A operations and through rollout to a safe taxi speed in CAT III B (and CAT III C when authorized).

Automatic landing is not CAT III. An automatic landing system is only equipment providing automatic control of the aircraft during the approach and landing and is not related to particular weather conditions. This system is mandatory for all CAT III operations. However, it is a common practice to perform automatic landing in good visibility but in that case, the ILS performance must be sufficient and ILS signals protected.


As for CAT II operations, for those who fly internationally ...

JAA = Europe
FAA = USA
ICAO = Everywhere else

CAT II DEFINITIONS

ICAO definition
A category II approach is a precision instrument approach and landing with decision height lower than 60m (200ft) but not less than 30m (100ft), and a runway visual range not less than 350m (1200ft).

FAA definition
A category II approach is a precision instrument approach and landing with decision height lower than 200ft (60m) but not lower than 100ft (30m), and a runway visual range less than 2400ft (800m) but not less than 1200ft (350m).

JAA definition
A category II approach is a precision instrument approach and landing with decision height lower than 200ft (60m) but not lower than 100ft (30m), and a runway visual range not less than 300m (1000ft).

CAT III A DEFINITIONS

ICAO and FAA definition
A category III A approach is a precision instrument approach and landing with no decision height or a decision height lower than 100ft (30m) and a runway visual range not less than 700ft (200m).

JAA definition
A category III A approach is a precision instrument approach and landing with a decision height lower than 100ft (30m) and a runway visual range not less than 700ft (200m).

It is worth noting that the JAA considers that CAT III A is always associated with a decision height (difference with ICAO/FAA).

CAT III B DEFINITIONS

ICAO and FAA definition
A category III B approach is a precision approach and landing with no decision height or a decision height lower than 50ft (15m) and a runway visual range less than 700ft (200m), but not less than 150ft (50m).

JAA definition
A category III B approach is a precision approach and landing with no decision height or a decision height lower than 50ft (15m) and a runway visual range less than 700ft (200m), but not less than 250ft (75m).

ICAO/FAA and JAA differ by the minimum RVR associated with CAT III B approaches (50m / 75m).
JAA: Where the DH and the RVR do not fall in the same Category, the RVR will determine in which Category (CAT III A or B) the operation is to be considered.
We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
 
EconoBoy
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RE: Foggy Landings - Attempts Or Just Divert?

Wed Nov 23, 2005 11:28 pm

Julesmusician, I wouldn’t count on EasyJet always landing in foggy conditions. On Monday, my flight to Bristol-Berlin flight was cancelled because the incoming plane (A319) decided to divert to Exeter because of the fog. Yet next day, the incoming plane (A319 again) arrived on time at Bristol, despite the fog being just as bad on that day. I guess it is down to whether the captain (and f/o?) are certified for CAT 3.
 
VuelingAirbus
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RE: Foggy Landings - Attempts Or Just Divert?

Thu Nov 24, 2005 3:29 am

Quoting Julesmusician (Reply 19):
Autothrust same as autothrottle?

Yes and no. Same thing but two different concepts. I a conventional jet you have the throttles to control thrust and if the automation takes over this task it controls the throttels (little motor which moves the levers for you). In the Airbus the levers are only contolled by the pilot. If you want the computer to control your thrust than the thrust lever will be in a fixed detend and do not move (thats why they call it Autothrust)

Quoting PhilSquares (Reply 18):
My answer was based on the WX prior to crossing the FAF or G/S intercept altitude. Once you're inside those points, it can go to 0/0 and you can still land

interessting conversation i must admit. Well maybe I missunderstand what qualifies as look and see. However the reason for a decision height is that you decide at this height. I would not recommend to continue and land in 0/0 when performing a CAT 2 approach and the fog got worse after you passed the marker (or fixed distance). You will loose your licence. I actually do have 0/0 in my licence and my previous company was approved for NO decision height and zero visibility.

Quoting Starlionblue (Reply 25):
LANDING in zero viz is fully feasible today. But now what? You're sitting on the runway. How exactly do you propose finding the turnoff, let alone taxiing to the gate? That's the problem.

And it is and was done by my company. Fog sometimes comes in patches and many times it even has a clear defined border. I saw it many times in Munich that the southern runway was CAVOK and the nothern runway CAT3. You can legally land in 0/0 with NO DH if only the touchdone zone is affected and the MID or END section are above minima to taxi for the respective airport.

rgds
 
julesmusician
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RE: Foggy Landings - Attempts Or Just Divert?

Thu Nov 24, 2005 5:45 am

The question that has arisen is on landing/take off - how do you actually keep the aircraft on the centre line if you can't see anything?
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
VuelingAirbus
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RE: Foggy Landings - Attempts Or Just Divert?

Thu Nov 24, 2005 7:03 am

on take off you have a minimum rvr for take off (125 m) to see the runway center line lights (cause its done manual) and during CAT3c with 0/0 you have the autopilot in roll out mode (autopilot uses the ILS signal to keep the plane on the centerline)...

rgds

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