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Guest A32X

CAT III ops

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Guest A32X

Dear Sirs,Could someone explain CAT III operations to me? I've got a few aerodrome booklets (Aerad Gatwick, Manchester.) In the front are green pages titled "aerodrome operating minima

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Guest A32X

Very interesting information but how do you know if the airport you are landing at supports CAT III operations? Also for CAT IIIA it say's DH is <100 or no DH, but where are these figures published? Finally what's TDZE, i.e. "set Baro to TDZE + 50ft" for CAT IIIA approaches.Thanks.

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Guest wkzzo

It will say so on the approach chart if its cat III, All info pertaining to the approach is included on the chart.TDZE is touch down zone of the runway.

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Guest A32X

Could you give an example of such a chart/link to a chart. I have yet to see a chart for CAT III approaches for a UK aerodrome.Thanks again.

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Go here; www.myairplane.com and see approach plates for the ICAO (airport indentifier) and you can view any approach chart, this is an example- http://www.myairplane.com/databases/approa...ORD_ir14R_3.pdf This is KORD (Chigago runway ILS 14L CAT III. TDZE 652' + 50'===== [h4]Best Wishes,Randy J. Smithhttp://www.precisionmanuals.com/images/forum/betaimg.jpg

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Guest Blue Ridge Dx

Hey Wallace,I'm a bit confused by your reply, perhaps i'm just misunderstanding you. But to clarify, Approach Category C and CAT IIIc are two entirely different things. The approach category (CAT C in your example) does not affect the RVR requirement for shooting the CAT III approach to 24R. In the example plate above, the minimum for ALL approach categories (A/B/C/D) shooting the CAT IIIa approach is RVR 700, for the CAT IIIb approach its RVR 600, and the CAT IIIc approach is Not Authorized.That said, on most other types of approaches (ILS CAT I, VOR, etc...) the Approach Category usually does increase the required minimum to fly the approach.Like I said, maybe thats what you meant, and i just didn't get it. If so, my apologies... ;)Best Regards,Nick LandolfiBlue Ridge Dx

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Guest A32X

So if your shooting the CAT IIIb ILS on the above plate (ILS 24R) what DH do you set? Also, I can't find any such charts giving these details for UK/European airports.-Paul

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Hi a CAT C Approch is based on approach speed..each a/c has a catagory (ABCD) based on its speed takes which ever path is shown on a plate.A cat IIIA/B/C Landing is compleatley different.at cat 3c autoland is exactly that and can land in zero Vizwith a RVR of 75m and a cat 3b is rvr 150.please correct me if im wrong (the 3b is definatly right)apparently you can find uk info on aip website. hope some of this info is of help"Lairy"Liam Reynolds

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Guest wkzzo

Not very positive on this ,but I dont beleive there is a DH for a CATIIIB certified aircraft(fail operational autoland), visual reference is not a requirement.A CATIIIB would be flown as a full autoland.On a CATIIIA aircraft(fail passive autoland) I think 50 ft would be the Missed approach if no Rnwy in sight.

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i just found this from Avionics Magazine.(http://www.avionicsmagazine.com/cgi/av/show_mag.cgi?pub=av&mon=0403&file=0403mls.htm) bottom of page"(Quote)""There are three categories, and one is broken down into three subcategories. They break down as follows:Cat I instrument approaches and landings allow a decision height of 200 feet (60 meters) and an RVR of 1,800 feet (550 meters). Cat II operations allow approaches and landings down to a decision height of 100 feet (30 meters) and an RVR of 1,200 feet (350 meters). Cat IIIa allows a decision height down to 50 feet (15 meters) and RVR of 700 feet (200 meters). Cat IIIb allows a decision height of 50 feet (15 meters) and RVR of 150 feet (50 meters). Cat IIIc allows a zero-foot decision height with an RVR of less than 150 feet (50 meters)." ("Unquote")"Lairy"Liam Reynolds

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Guest wee_davie_2612

Here's what I've got about the different landing catagories (quoted from someone, although I have no idea who):"ILS Categories -Cat.I - 200 feet DH - 2,400 feet (or 1,800 feet) RVRMetric: 800 metres of 550 meters RVRCat II Restricted - 150 feet DH - 1,600 feet RVRMetric: 500 metres RVRCat II - 100 feet DH - 1,200 feet RVRMetric: 350 metres RVRCat.IIIa - 700 feet RVR - no DH (alert height generally 50 feet)Metric: 250 meters RVRCat.IIIb - 600 feet RVR - no DH (alert height generally 35 feet)Metric: 175 metres RVRCat.IIIc - zero ceiling, zero visibility - "blind" landingRVR 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 ;ppl out the window and make a DECISION to land or go-around depending wether or not you can actually see the runway. 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...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...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."Aircraft catagories are a different beast altogether. Your aircraft catagory is based on: 1.3Vso (kts IAS) (Vso is landing config stall speed). Incedently Vref is also 1.3Vso which makes it easy to find out your catagory of aircraft. The catagories go like this:A = Vref <91 kts indicatedB = Vref 91-121 kts indicatedC = Vref 121-141 kts indicatedD - Vref >141 kts indicatedSo in the case of the NG's, the typical Vref is about 130kts (give or take) so it is a CAT C aircraftFor the person who asked about the minima on UK charts, here you go:http://forums.avsim.net/user_files/69487.jpgI can't remember what the 'OC' in 'OCA' stands for but the bold numbers are DH as shown on the baro altimeter and those in brackets ar Radio alt heights.I hope this helps :)CheersDavid

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Guest wkzzo

This is my understanding of the requirements for the usa: 1) CAT IIIA - DH below 100 feet or no DH and RVR not less than 700 feet2) CAT IIIB - DH below 50 feet or no DH and RVR not less than 150 feet3) CAT IIIC - no DH and no RVR limitation

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Guest mmcevilley

>TDZE is touch down zone of the runway.TDZE is the elevation of the touch-down zone portion of the runway.-michael

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Guest wee_davie_2612

P.s. Paul (A32X), I forgot to mention. The reason that you don't see DH's listed for CAT III approaches is because, as stated in my post above, in these situations there is no DH, only alert height.CheersDavid

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David,"I can't remember what the 'OC' in 'OCA' stands for but the bold numbers are DH as shown on the baro altimeter and those in brackets ar Radio alt heights."OC = Obstacle clearanceOCA = Obstacle clearance AltitudeOCH = Obstacle clearance HeightCheersBill

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Guest wee_davie_2612

Thanks Bill :)David

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