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Wedge
26th Aug 2001, 17:18
A relative of mine was forced to hold for 45 minutes over Jersey on Friday evening due to fog and eventually had to return to Gatwick as it failed to lift.

Although I have flown into Jersey several times (as pax) I have never had this problem, but I know it happens quite frequently. So my question is for some helpful pilot who can explain is:

What exactly are the Landing category minima for Cat 1, 2, and 3? What do the letters A, B and C signify - eg LHR which is Cat 3C, which I understand is the Category for landing in the lowest visibility (200 metres RVR?).

Is the problem at Jersey just the runway length (about 1500 metres) or are there specific avionics that it does not have installed - I can't imagine it would be the latter as the spend a lot of money on the airport!

Thanks in advance.

spoilers yellow
26th Aug 2001, 19:08
There are number of components that make up the requirements that would satisfy an airfield being CAT 2or3


1. The aircraft itself must be capable of performing a cat 3 approach(usually with autoland)this requires a visibilty down the runway of 200m(cat3A), 150m(cat3B), or lower which would be cat3C, they all need a height above the runway of around 50FT at which the pilots must be able to see at least some component of the runway lighting system in order to make the decision to allow the aircraft go land itself.


2.Both pilots on board must be trained in the simulator in cat2 or cat3 approach operations and both must have practised doing them in good weather in the recent past(usually one a month)


3. The airport itself must have an Instrument Landing system (ILS) that is capable of allowing an aircraft to make an automatic landing. The runway must also be of certain size and have adequate lighting systems.

4. The terrain surrounding the airport, particularly the part under the final approach has to be pretty uniform in height as the landing systems rely heavilly on Radio Altimeter information which measures height above the ground by bouncing radio waves off the land beneath the aircraft.

Finally you do not say which airline you flew with, but if it was a (fully servicable, British Airways RJ100 it would be cat3. If it was a British European 146 I think they are only cat2)
Unfortunately all that said Jersey is only a Category ONE airfield so no matter how fancy the aircraft, the pilots still need a runway visibillity of around 550metres and they must be able to see the ground by 200ft above the airfield.If this is not the case then I am afraid you end up doing exactly what you did much to the annoyance of your company and lots of fare paying passengers who can usually see all the island except the bit thar you are trying to land on!!

Hope this helps, I would be pleased to answer any bits I have missed out. :confused:

[ 26 August 2001: Message edited by: spoilers yellow ]

Wedge
26th Aug 2001, 20:38
Thanks Lear 23 and spoilers yellow, very helpful - as I suspected it is a little complictated. I am surprised, however, that Jersey has not taken the decision to upgrade their ILS category. I presume this would be very expensive but as you say Lear 23 there must be a huge impact on the island and especially the airlines whenever this happens.

Airline was British European - however not sure of the type as it was not me who was flying in this case.

Could you also explain exactly what features are necessary to make an aircraft Cat 2/3 capable, and what avionics exactly are required to make the ILS installation the same - ie what are the differences between a Cat 1 ILS and a Cat 2/3?

Even if Jersey did install a Cat 3 ILS, would there still be a problem in using it below a certain vis because of the short runway length?

Pointer
26th Aug 2001, 22:09
Ground equipment:
cat1 and other cat landings ILS is the same except for the failsave items (even if one component of the system breaks down or is outside the set parameters, there should be a backup system-component) and those differ from cat II and III. then you have to have signal integrity; no disturbance allowed, it might 'bend' the localiser beam or the glide-slope. so you need a interference free area. But the terain surrounding the threshhold is of great importance too!(i beleive as said above.)

for an aircraft it is not very hard to become catII but catIII is much more costly and involves systems only installed on larger jets. for small commuter planes lets say up to 70 seats the investment is too high regarding theire yeild.

so as jersey is mostly visited in the summer and mostly by a limmited size A/C, and the rwy is not of the flat kind......you can gues its too........

spoilers yellow
26th Aug 2001, 23:22
There are various systems on board that an aircraft must have servicable on an auto approach, they must have at least two autopilot systems (usually three) all monitoring each other, the aircraft will have auto throttles although on the aircraft I fly it is possible to autoland using manual thrust control.
As I mentioned before the majority of actions that the aircraft goes through on the approach e.g. aligning the nose with the runway centre line and flaring into the landing attitude are all done with reference to the Radio altimeter which measures height above the ground directly below the aircraft, so it goes without saying that these must be fully servicable.

This leads on to your next point about Jersey becoming cat 2 or 3.

I think that for a start the runway might not be of sufficient width ( not 100% on that) and more importantly as Pointer mentioned the signal emitted from the ILS ground installation must be protected from other aircraft, namely those ones sitting at the holding point waiting for departure. Large chunks of metal, such as aircraft are capable of bending the beam of the ILS possibly resulting in an undesirable low level fly by of St Hellier!!.
Jersey as as it stands at the moment does not have a holding point far enough from the runway to achieve this ILS protection.

Back to the Radio altimeter point, the approach to both runways at Jersey comes in over rapidly undulating terrain.The problem that this creates is that the height that the radio altimeter is indicating ( and therefore the point that the aircraft flares etc) is not correct, this is particularly the case when landing on the easterly rwy that approaches over the beach. one minute the Rad-alt is indicating 2000ft then in a matter of seconds it decreases to less than 100 ft and by this point the aircraft systems have not done a number of things that they should have.

Therefore we reference all our cat 1 approaches on height above sea level (altitude) which is not affected by terrain.

So in answer to your question an upgrade to Cat 2 0r 3 would for a start only be possible on to the westerley runway and even then new taxiways would be required with new holding points and even then I am not sure if the terrain below the approach is adequately uniform.

I have probably only confused the situation, but I hope this helps a little.

[ 26 August 2001: Message edited by: spoilers yellow ]

15/15 flex
27th Aug 2001, 01:01
In a similar vein, how many airports currently have Cat III with DH? We are in the process of developing Cat III procedures, and have not been able to come up with any examples. I understand you can have a minimum as low as 15', but how practical is this? Any large ac attempting a Go Around at that point WILL touch down - the autopilot is already in the flare and retard mode if an autoland is being performed. Any thoughts greatly appreciated.

spoilers yellow
27th Aug 2001, 13:19
The aircraft I fly is cat 3B we have a DH of 50ft and we require an RVR of 150m.

Some of our company aircfaft are cat3A, they need 200m RVR but still have a DH of 50ft.
On the other hand the 777 is cat 3C and they (I think) only need an RVR of 75m and have a zero DH, and even with a 50 ft DH and a heavy aeroplane the wheels have been known to touch the ground, they definately do when we practice engine failures in the simulator, and have to go around on three engines.


I think it is usually the aircraft and the company that determine the minima not the airport, so I am not to sure exactly what you are asking.
As I understand things if an airfield is cat 3, and we as an operator have cat 3 minima for that airfield then we are permitted to operate to our cat3(B) mimima.

wysiwyg
27th Aug 2001, 13:52
Spoilers yellow - the 757's I fly are approved for no DH and 75/0/0 meters RVR but they are still CAT 3B. I don't think 3C actually exists at present.

With regard to CAT 3B with a DH, I think you'll find that some countries (like Germany) don't allow CAT 3B no DH approaches.

Regards
wizzy

fireflybob
27th Aug 2001, 21:28
It's a while since I took a really close look at all this and most of the requirements have already been listed.

However, another element is runway lighting. For example, every other centreline light has to be on an alternative circuit so that, in the event of a failure, you only lose half the available lights. A further requiremnt is that power must be restored to the failed component within (I think) 15 seconds or so - makes sense really?

One presumes that the authorities at JER have looked at the feasability of CAT 2/3 there but if by any chance they haven't they ought to given the wx record!

Hotel Mode
27th Aug 2001, 23:15
I think there is work at present at Jersey to realign taxiways at the 27 end to provide protection for CAT 2 approaches to 27, which should make it a bit easier.

Wedge
28th Aug 2001, 00:38
Thanks a lot for all the input guys, answers all my questions.

The building work is well underway at Jersey to realign the taxiway at the 27 end of the airport so this may indeed be with a view to making 27 Cat 2 certificated - as you say fireflybob it's about time!

wysiwyg
28th Aug 2001, 16:05
Standby power must restore the equipment within 2 seconds.

The reduced RVR requirement on RWY 27 is due to the better approach lighting facilities provided on the approach path to that runway
Rather than 27 having a reduced RVR, 09 has an increased RVR requirement as there are cliffs immediately before the threshold which mean that there is only a very reduced set of approach lights available. CAT 2 ops require visual contact with three consecutive sets of lateral approach lights and as these do not exist on 09 that runway will never get CAT 2.

I think there is work at present at Jersey to realign taxiways at the 27 end to provide protection for CAT 2 approaches to 27, which should make it a bit easier
I was under the impression that the reworking of the taxiways at the east end of the field was mainly to provide a surface with greater load bearing capacity as at present A320 size aircraft and above have to enter the runway earlier and back track due to both reduced wing clearance and wheel/weight distribution. Isn't this also the area planned for further development, hence need for improved taxiways?

Regards
wizzy

Oilhead
1st Sep 2001, 18:52
My understanding is that "3C" will have nothing to do with the aircraft - it is already landing - it couldn't care less what the visibility is. The move to "3C" will be dictated by ground facilities, particularly the problems associated with seeing where the hell you are after landing and having cleared the runway. FOr many autoland operations, there is no requirement to see anything prior to touchdown, hence the "Alert Height" - (the Frogs do have that requirement hence a "Decision Height"). Past experience has shown that the problems begin after thinking you have cleared the runway. Ask United about pilot disorientation after landing in low vis. In Cat 3C, SMIGS would be useless - you wouldn't be able to see a foot in front of your face.

M.Mouse
1st Sep 2001, 22:05
spoilers yellow,

You said '1. The aircraft itself must be capable of performing a cat 3 approach(usually with autoland)this requires a visibilty down the runway of 200m(cat3A), 150m(cat3B), or lower which would be cat3C, they all need a height above the runway of around 50FT at which the pilots must be able to see at least some component of the runway lighting system in order to make the decision to allow the aircraft go land itself.'

Although you go on to correct yourself in a later post and it has been pointed out by others, 0' DH and 75m RVR is a common minima. It is on my fleet - 757/767.

My personal record is 125m and I saw nothing until the nosewheel landed. Taxiing in fog with RVR below 200m is not easy and 75m must be bordering on the impossible!

Nobody seems to mention and I don't know the answer either but JER's runway is not very flat. It has significant undulations which might well preclude autolanding anyway even if the equipment/protection was in place.