YYZatcboy
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ILS Landing System

Fri Apr 22, 2005 5:25 am

Hey everyone
I was just wondering if anyone could let me know what exactly a cat 1,2,3 ILS means.
Thanks
DHC1/3/4 MD11/88 L1011 A319/20/21/30 B727 735/6/7/8/9 762/3 E175/90 CRJ/700/705 CC150. J/S DH8D 736/7/8
 
CO737
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RE: ILS Landing System

Fri Apr 22, 2005 6:14 am

Catergories refer to the minimums for the ILS. CAT I are your standard minimums (200 ft. AGL and 1 mile visibility). CAT II have lower minimums (100 and 1/2, I believe). CAT III don't have a ceiling requirement, but are based on the runway visual range. Any instrument rated pilot can shoot a CAT I, but CAT II and III approaches require special training and aircraft equipment.
 
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Starlionblue
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Joined: Fri Feb 27, 2004 9:54 pm

RE: ILS Landing System

Fri Apr 22, 2005 8:42 am

Here's some more data stolen from old posts.

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." - John Ringo
 
PhilSquares
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RE: ILS Landing System

Fri Apr 22, 2005 8:59 am

Quoting Starlionblue (Reply 2):
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.

All the -400s come from Boeing with the capability for CAT IIIC. The operator's ops specs might not be for CATIIIC but for a lower category. That lower category would then become limiting factor.

For example at SQ, we are CATIIIB with an alert height of 20'.
Fly fast, live slow
 
Boeing7E7
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RE: ILS Landing System

Fri Apr 22, 2005 9:07 am

CAT I/II - ILS, Terrain, Aircraft Equipment, Approach Lights and Crew based minima.

CAT II is nothing more than a CAT II with additional pilot qualifications.

Explaining TERPS is a real pain in that I can't send you to a direct document as the FAA has seen fit not to make all of the publications available to the general public. If you ask a FSDO they may provide you with a copy of the TERPS manual the FAA uses to define approach minima, slopes and system criteria.

There are about 8 components that make up the TERPS standard which enables the Category of ILS approach. For example. CAT I/II only requires ALSF-I approach lights, CAT II/III is ALSF-2. A simple variation in the airfield altitude changes the dynamics of the approach surface exponentially.

Here's a link where you can get some very basic info on TERPS. The basic document is the 8260, but it's not all there. It's as if they don't want some farmer with a landing strip is goign to go out and trying to get his own CAT III approach or something:

Basic TERPS 8260.3B(Sections not included):

http://av-info.faa.gov/terps/directives%20page.htm


Very Very Basic CAT II/III TERPS:

http://av-info.faa.gov/terps/Policies1/TIL00005Aatt.PDF
 
MD11Engineer
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RE: ILS Landing System

Fri Apr 22, 2005 9:14 am

Quoting Starlionblue (Reply 2):
Here's some more data stolen from old posts.

Looks like 747Skipper!  Wink

Jan
Je Suis Charlie et je suis Ahmet aussi
 
Fly2HMO
Posts: 7207
Joined: Sat Jan 24, 2004 12:14 pm

RE: ILS Landing System

Fri Apr 22, 2005 12:16 pm

Has any FAA official seen my signature yet? 
The problem with the CATIIIC system is that you might find the runway blindfolded, but will you find the gate? Big grin

[Edited 2005-04-22 05:18:22]
 
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HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: ILS Landing System

Fri Apr 22, 2005 2:02 pm

Quoting MD11Engineer (Reply 5):
Looks like 747Skipper!

Too bad Hes not gettng back.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
Boeing7E7
Posts: 5512
Joined: Sat Jul 31, 2004 9:35 pm

RE: ILS Landing System

Fri Apr 22, 2005 11:17 pm

Quoting FLY2HMO (Reply 6):
The problem with the CATIIIC system is that you might find the runway blindfolded, but will you find the gate?

It does exist. It's called MITL, SMGCS and RWSL.

Might want to change your signature.
 
Boeing7E7
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Joined: Sat Jul 31, 2004 9:35 pm

RE: ILS Landing System

Sat Apr 23, 2005 12:33 am

I should also add that the US just shit canned another landing system LAAS for the short term. After wasting 7 years with Raytheon and 2 years with Honeywell they magically discovered that LAAS as envisioned would not provide CAT III capability. Nice. Real nice. MLS anyone???? AGAIN!!!!!!!!!!!

Although with MMR's, FMS, WAAS, IRS/INS and MLS accuracy.... Imagine the possibilities.... Hello FAA... Anyone listening?????
 
Glom
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RE: ILS Landing System

Sat Apr 23, 2005 3:05 am

Is it the case that in a CAT IIIc approach, autoland must be used, or could a suitably skilled pilot hand fly such an approach?
 
saab2000
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RE: ILS Landing System

Sat Apr 23, 2005 4:26 am

When I flew Saab 2000s in Europe, we were certified to CAT IIIa minimas. It was handflown with a HUD - Head Up Display. If the flying pilot (always the captain in the case of the Saab 2000) deviated enough, it caused a "Loss of Approach" warning and a go-around was required.

It was a fairly simple operation to be honest, and we never had to go around.

I cannot speak of other categories of approaches, but the CAT IIIa approaches on the Saab2000 are hand flown.
smrtrthnu
 
Boeing7E7
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Joined: Sat Jul 31, 2004 9:35 pm

RE: ILS Landing System

Sat Apr 23, 2005 4:37 am

Quoting Glom (Reply 10):
Is it the case that in a CAT IIIc approach, autoland must be used,

Yes. Enhanced Vision (FLIR) may change that.

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