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What To Do In A Foggy Condition?  
User currently offlineUAEflyer From United Arab Emirates, joined Nov 2006, 1084 posts, RR: 1
Posted (7 years 9 months 2 days 22 hours ago) and read 3069 times:

As all of us know that London Heathrow Airport is covered by fog for the past three days.
My question here is how do the aircrafts operate in a foggy weather and how can the pilot identify the runway, how he could ground the aircraft?

What about the safety distance between the aircrafts, is it the same as a normal day (LHR i think every minute a landing).
How do the control tower works?
What is the latest technology in airports & aircrafts that help in such situation

16 replies: All unread, jump to last
 
User currently offlineSevenair From United Kingdom, joined Feb 2001, 1728 posts, RR: 0
Reply 1, posted (7 years 9 months 2 days 21 hours ago) and read 3059 times:

They user ILS/MLS - usually with full autoland where available when the weather is like this. The tower user Secondary Surrveilance Radar to provide separation during the approach, the the usual separations doubled when in poor visability. And this doubled distance is what leads to delays as capacity is much reduced.

On the gorund, the tower use ground radar which in some instances, they can see the acutal type of aircraft by its radar footprint, using a primary radar. Planes also need to move away from the ILS Critical area which is extended depending on the type of operations (CAT I II or III) which causes further delays.

I blieve some ac have a synthtic view of the field, much like the screens in fighterjet pilots have in their helmets - however, the only one I have seen this on wa a test Do328 - years ago  Smile


User currently offlineUAEflyer From United Arab Emirates, joined Nov 2006, 1084 posts, RR: 1
Reply 2, posted (7 years 9 months 2 days 21 hours ago) and read 3035 times:

Quoting Sevenair (Reply 1):
They user ILS/MLS - usually with full auto-land where available when the weather is like this. The tower user Secondary Surrveilance Radar to provide separation during the approach, the the usual separations doubled when in poor visability. And this doubled distance is what leads to delays as capacity is much reduced.

Well i am not a pilot, but as i know that the auto-pilot system do not land/take-off the aircraft? and is it safe to depend on the system to ground the aircraft especially the heavy equipment like 744- 346...etc


User currently offlineSevenair From United Kingdom, joined Feb 2001, 1728 posts, RR: 0
Reply 3, posted (7 years 9 months 2 days 20 hours ago) and read 3015 times:

Some systems can take the aircraft down the the ground, and stop the aircraft straight on the runway, the brakes being disconnected by pilot action. As for the takeoff, I believe it is not uncommon for the plane to fly automated from about 200 foot. If your plane is landed fully automated, it must have a "fail safe/active" capability, so if a systems fails or encounters a problem it can land on the remaining computers. If you have fail pasinisive, the minima are greater and if you have a computer related fault, you MUST go around.

No disrespect to anyone out there, but a computer can often fly the plane more accuratly than the pilot, with many airlines insisiting the plane be flown automatically once airbourne in the interests of "passenger comfort".

Although runway incursions are on the up, accidents of this nature are very rare (worst ones being the KLM/Pan Am crash and the SAS/Private jet crash in Linate). The only option apart from flying this way is not to fly at all.


User currently offlineUAEflyer From United Arab Emirates, joined Nov 2006, 1084 posts, RR: 1
Reply 4, posted (7 years 9 months 2 days 20 hours ago) and read 2991 times:

Quoting Sevenair (Reply 3):
If you have fail pasinisive, the minima are greater and if you have a computer related fault, you MUST go around.

your post if very informative, but you could you please clarify this, i mean more details and example would make it better


User currently offlineSevenair From United Kingdom, joined Feb 2001, 1728 posts, RR: 0
Reply 5, posted (7 years 9 months 2 days 19 hours ago) and read 2971 times:

Thanks - I just passed my Operation Procedures exam a few months ago, and I'm studying for air law - what a chore!! For example, a Cat I approach needs a RVR of 550m with full runway lighting on high intensity setting - and a descision height of 200ft.

Cat IIIB needs just 75m RVR and a descision height of <50ft on the radio altimeter. Cat IIIC is very rare but has a desision height of 0ft (!) and an RVR of 0ft (!) but this is difficult as taxiing is very difficult with a visibility of less than 75m.

Which approach type is used depends on lots of things : aircraft type and equipment, airport equipment, crew certification and currency as well as ATC capapbility.

[Edited 2006-12-23 12:48:17]

User currently offlineUAEflyer From United Arab Emirates, joined Nov 2006, 1084 posts, RR: 1
Reply 6, posted (7 years 9 months 2 days 16 hours ago) and read 2888 times:

Quoting Sevenair (Reply 5):
Cat IIIB needs just 75m RVR and a descision height of <50ft on the radio altimeter. Cat IIIC is very rare but has a desision height of 0ft (!) and an RVR of 0ft (!) but this is difficult as taxiing is very difficult with a visibility of less than 75m.

and what airport have these systems? do LHR have them?
i heard that DXB have a cat III but i dont know if it is B or C


User currently offlinePs76 From , joined Dec 1969, posts, RR:
Reply 7, posted (7 years 9 months 2 days 15 hours ago) and read 2873 times:

Hi - I heard last night LHR Atis having "CATIII holding points in use", also a few words like "Teperature Inversion Exists Above the Runway" (although have no idea what it was intended for).

P.

[Edited 2006-12-23 16:45:12]

User currently offlineVikkyvik From United States of America, joined Jul 2003, 10029 posts, RR: 26
Reply 8, posted (7 years 9 months 2 days 15 hours ago) and read 2858 times:
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Quoting Ps76 (Reply 7):
also a few words like "Teperature Inversion Exists Above the Runway" (although have no idea what it was intended for).

In a standard atmosphere, the temperature drops as you go up in altitude (up to the top of the troposphere, at around 36,000 feet I think). If a temperature inversion exists, it means that the temperature actually INCREASES as you go up from the ground, up to some altitude, at which point the temperature starts decreasing again like normal.

Clouds typically form when rising water vapor reaches an altitude where the temperature equals the dew point, causing the water vapor to condense into clouds. In a temperature inversion, since the temperature at the ground is lower than the temperature above it, it could be equal to or lower than the dew point, causing water vapor to condense, creating ground fog.

Least, that's what I remember from my "Atmospheric Environment" class.

~Vik



"Two and a Half Men" was filmed in front of a live ostrich.
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17040 posts, RR: 66
Reply 9, posted (7 years 9 months 2 days 15 hours ago) and read 2853 times:

It's important to remember that while landing in zero viz is feasible, there is no facility which allows taxi in zero viz. So unless you can see at least a little bit, there's really no point landing even if you can unless it's an emergency.

Another factor is that certification for Cat III ops needs to be obtained for the runway, the aircraft and the pilots. So while the airport may allow Cat III ops, the pilots and/or aircraft may not be certified at that time. One example would be if some part of the autoland system is broken at that time. That aircraft can still be hand flows to a landing, but not if Cat III conditions exist

Here is some ILS info stolen from a very old post:


Aviation - ILS Categories

xxx
Cat.I - 200 feet DH - 2,400 feet (or 1,800 feet) RVR
Metric: 800 metres of 550 meters RVR...
xxx
Cat II Restricted - 150 feet DH - 1,600 feet RVR
metric: 500 metres RVR
xxx
Cat II - 100 feet DH - 1,200 feet RVR
Metric: 350 metres RVR
xxx
Cat.IIIa - 700 feet RVR - no DH (alert height generally 50 feet)
Metric: 250 meters RVR
xxx
Cat.IIIb - 600 feet RVR - no DH (alert height generally 35 feet)
Metric: 175 metres RVR
xxx
Cat.IIIc - zero ceiling, zero visibility - "blind" landing...

RVR is Runway Visual Range, basically a distance in feet that the pilot can expect to see forward in his airplane.


The ILS equipment at the airport must be certified for it, as well as aircraft type (actually individual aircraft) and crew have to be certified.


Alert Height (AH) is not like a Decision Height (DH) -
At "DH" (obtained from radio altimeter for Cat.II) you have to make a DECISION to land or go-around...
xxx
In Cat.III operations, there is no DH... but you have to make a decision to land based on "what you see"... pilots find the DH "decision" very convenient for Cat.II, but did not exist for Cat.III...
xxx
So in "pratical operations", the AH is used somewhat like a DH, but is not regulatory. In other terms, we expect to "see the runway" at that point... which is about 50 feet radio altimeter, just about where the runway threshold is located, in Cat.IIIa minimums. In Cat.IIIb, happens at about 35 feet...
xxx
Many 747 are equipped for Cat.IIIa operations (not Cat.IIIb), although most of the "Classic" 747s (with 3 autopilot channels) have the LRCU that is required for Cat.IIIb... LRCU = landing roll control unit... keeps the nose wheel on the center line, using the localizer...



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineTheGreatChecko From United States of America, joined Mar 2004, 1128 posts, RR: 2
Reply 10, posted (7 years 9 months 1 day 7 hours ago) and read 2718 times:

Landed yesterday in ANC with 1 1/4 mile vis. While that visibility is still pretty good, the procedures for landing would be the same.

Much of this is predicated by the procedures of each airline and what they can and cannot according to regulations, so this will really be a general outline.

First, you have to ensure that the weather at the airport will allow you to even attempt the approach. Here we cannot fly the approach if the visibility is below the minimum allowed.

Air traffic control clears you for the approach and, if necessary, the transition to the approach, which basically takes you to the localizer (a navigation signal aligned with the runway) while ensuring terrain clearance.

Once on the approach one pilot flies the plane while the other is looking outside, watching for the runway lights or when you are lucky the runway itself. The non-flying pilot is also monitoring the airspeed and navigation equiptment and verbalizing any deviations to make sure the flying pilot notices them.

When the runway or runway lights are in sight, the non-flying pilots says, "Runway lights in sight" or "Runway in sight." At that point the pilot-flying looks up and then visually flies the plane to the runway.

If the runway is not seen before the minimum alititude or missed approach point, the pilots execute a go-around and fly a charted procedure to a holding point or get vectors from ATC to try the approach again or to proceed to another airport.

Once on the ground, taxing is done very carefully with both pilots having their taxi diagrams out and carefully verifying and following directions from ATC.

Quoting Ps76 (Reply 7):
Hi - I heard last night LHR Atis having "CATIII holding points in use",

A Cat-III holding point is just a line painted on the ground with signs at the side indicating where an aircraft needs to stop when Category III operations are being conducted.

Similar to the hold lines at the perimeter of the runway for normal operations, they are further away from the runway to give the aircraft landing more room and, more importantly, ensure that the aircraft waiting to depart do not block or affect the localizer and glideslope signals. Category III operations are very precise and really dont allow much room for error, but to ensure safety lots of room is given to the landing aircraft.

Checko



"A pilot's plane she is. She will love you if you deserve it, and try to kill you if you don't...She is the Mighty Q400"
User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 11, posted (7 years 9 months 1 day 3 hours ago) and read 2683 times:

Quoting Starlionblue (Reply 9):
So in "pratical operations", the AH is used somewhat like a DH, but is not regulatory. In other terms, we expect to "see the runway" at that point... which is about 50 feet radio altimeter, just about where the runway threshold is located, in Cat.IIIa minimums. In Cat.IIIb, happens at about 35 feet...

I have to disagree a little Starlionblue, at least for us, the diff in mins for IIIa & IIIB is rollout guidance and AH stays the same 100'RA. The Ah is your final confirmation that the a/c is in the correct position to land that 's all (all parameters are correct in the cockpit). IIIA (W/O rollout requires visual contact before landing), IIIB (w/ rollout control) does not require vis before landing.


User currently offlineBond007 From United States of America, joined Mar 2005, 5417 posts, RR: 8
Reply 12, posted (7 years 9 months 1 day 3 hours ago) and read 2679 times:

Quoting Starlionblue (Reply 9):
It's important to remember that while landing in zero viz is feasible, there is no facility which allows taxi in zero viz.

It's amazing isn't it. We can land a 200 ton aircraft completely automatically to within a few feet accuracy, but we can't taxi to the gate  Wink

The new EVS products look interesting though for 'looking' through fog.


Jimbo



I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
User currently offlineThrottleHold From South Africa, joined Jul 2006, 657 posts, RR: 1
Reply 13, posted (7 years 8 months 4 weeks 17 hours ago) and read 2531 times:

Quoting UAEflyer (Reply 2):
but as i know that the auto-pilot system do not land/take-off the aircraft

The auto-pilot can land, but not take-off.

Quoting Sevenair (Reply 5):
Cat IIIB needs just 75m RVR and a descision height of <50ft on the radio altimeter. Cat IIIC is very rare but has a desision height of 0ft (!) and an RVR of 0ft (!) but this is difficult as taxiing is very difficult with a visibility of less than 75m.

CAT IIIb approaches can be flown with or without a DH. It is possible to fly a CAT IIIb with no DH and an RVR of 75m.
CAT IIIa requires a DH of no less than 50ft, but also an RVR of 100m.

Quoting Starlionblue (Reply 9):
Cat.I - 200 feet DH - 2,400 feet (or 1,800 feet) RVR
Metric: 800 metres of 550 meters RVR...
xxx
Cat II Restricted - 150 feet DH - 1,600 feet RVR
metric: 500 metres RVR
xxx
Cat II - 100 feet DH - 1,200 feet RVR
Metric: 350 metres RVR
xxx
Cat.IIIa - 700 feet RVR - no DH (alert height generally 50 feet)
Metric: 250 meters RVR
xxx
Cat.IIIb - 600 feet RVR - no DH (alert height generally 35 feet)
Metric: 175 metres RVR
xxx
Cat.IIIc - zero ceiling, zero visibility - "blind" landing...

Those are all wrong.
DH / RVR
CAT I...........................200ft / 550m
CAT II..........................100ft / 300m
CAT IIIa.........................50ft / 200m
CAT IIIb (with DH)............50ft / 125m (I think!)
CAT IIIb (without DH).......none / 75m
CAT IIIc.........................none / 0m

Quoting Starlionblue (Reply 9):
In Cat.III operations, there is no DH... but you have to make a decision to land based on "what you see"... pilots find the DH "decision" very convenient for Cat.II, but did not exist for Cat.III...

DH does exist on CAT III, see above.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17040 posts, RR: 66
Reply 14, posted (7 years 8 months 4 weeks 15 hours ago) and read 2509 times:

Quoting Bond007 (Reply 12):
It's amazing isn't it. We can land a 200 ton aircraft completely automatically to within a few feet accuracy, but we can't taxi to the gate

Indeed. Although if you think of emergencies, getting on the ground is more critical than taxiing to the gate.

There are several new systems for zero viz navigation being developed. You'd have to equip all vehicles with the system. One must bear in mind, though, that "true" zero viz is pretty rare.

Quoting ThrottleHold (Reply 13):
Those are all wrong.

Sorry about that. I said I stole it from an old post. I blame the original poster.  Wink



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineAAR90 From United States of America, joined Jan 2000, 3474 posts, RR: 46
Reply 15, posted (7 years 8 months 4 weeks 15 hours ago) and read 2498 times:

Quoting UAEflyer (Thread starter):
My question here is how do the aircrafts operate in a foggy weather and how can the pilot identify the runway, how he could ground the aircraft?

Electronics... or in aviation world they are called avionics.  Wink

Quote:
What about the safety distance between the aircrafts, is it the same as a normal day (LHR i think every minute a landing).

Separation is larger for IFR operations than VFR operations.

Quote:
How do the control tower works?

Same as almost every other day. The primary difference is that when operating VFR the controllers will rely upon their eyesight primarily and when IFR they must rely primarily on their electronics.

Quote:
What is the latest technology in airports & aircrafts that help in such situation

Transponders and accurate displays.



*NO CARRIER* -- A Naval Aviator's worst nightmare!
User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 16, posted (7 years 8 months 4 weeks 11 hours ago) and read 2472 times:

The CATIIIA & B can be confusing and diff operators may use diff policies but for us we quit using A & B . It's just a CATIII W or W/O rollout since that determines RVR mins. W/o rollout the RVR mins(for us) 600'(200m) but adequate visual cues are needed to land. W/ rollout we can go to 300' or 175m (75m if the app. allows) but all RVRs are controlling and and no visual cues required. The A/H is 100'RA for all CATIIIs.

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