GentFromAlaska
Topic Author
Posts: 2666
Joined: Sun Feb 20, 2005 2:21 pm

CAT III Navigation

Tue Feb 21, 2006 6:38 am

I'm attempting to educate myself on the difference between CAT III and RNAV navigation. CAT III as I understand it the actual navigation equipment onboard newer aircraft. CAT III It is further broken down to CAT III (a) and or (b); depending on the aircraft type. If a CAT III approach is used the airport has to be a CAT III rated airport. If this is a true statement can someone direct me to to a site where I can find CAT III rated/approved airports. I checked the FAA site but couldn't find much.

RNAV as I understand it is a point to point or beacon to beacon navigation system, Loran is supposibly a form of RNAV where a navigation fix is taken from several points. the location of the aircraft or vessel is where the points intersect.

I also saw a ref for RNAV made to RNP and also to Loran and Omega. RNP as I understand it newer which uses GPS technology whereas Loran dates back to 1960's and 1970's
Man can be taken from Alaska. Alaska can never be taken from the man.
 
corey07850
Posts: 2335
Joined: Wed Feb 04, 2004 4:33 am

RE: CAT III Navigation

Tue Feb 21, 2006 6:51 am

CAT III is a type of ILS, not navigation per se... Yes, a CAT III approach requires CAT III ground equipment, aircraft, as well as crew training.

RNAV, or area navigation is like you said, a point to point navigation. It can be anything from INS, LORAN, GPS, VHF RNAV, etc, etc. You are essentially correct on how Loran works. It takes the time delay from master and slave transmitters to "draw" parabolas... where the parabolas intersect is where the aircraft or ship is located.

RNP stands for required navigational performance... It is used to determine the accuracy for certain navigation devices (GPS)... For example, to use a GPS for an IFR approach it needs to have an RNP of .5... if it doesn't have this, then the GPS cannot legally be used for the approach.
 
bman351
Posts: 31
Joined: Mon Nov 08, 2004 2:46 am

RE: CAT III Navigation

Tue Feb 21, 2006 6:54 am

RNAV is usually a GPS approach. GPS usually being an overlay approach (usually NDB at airports in Canada). a CAT III approach is a type of ILS. CAT I has glide and localizer indications minimums on a CAT I are usually 200 ft., CAT II is the same indications, however in order for it to be a CAT II the RWY must have centre line RWY lighting and different approach and threshold lighting. CAT II approaches usually have 100ft minimums. CAT III must have additional lighting to this yet and is along the same lines as a CAT I and II approach. CAT III airports in Canada are YYZ and YVR, medium sized airports such as YWG are CAT II approved and the smaller aiports in Canada are mostly VOR/DME, NDB, ILS CAT I and LOC Backcourse.
 
bravogolf
Posts: 359
Joined: Thu Apr 21, 2005 6:18 am

RE: CAT III Navigation

Tue Feb 21, 2006 7:04 am

RNP is just starting to be used at some airports. All the equipment is onboard the aircraft. Basically you use GPS and the flight management computer. The pilots as well as the aircraft must be certified to use the approach. GYY has had Jepperson design a turning descending approach to our RW 12 and it should be in service shortly.
 
Mir
Posts: 19093
Joined: Mon Jan 05, 2004 3:55 am

RE: CAT III Navigation

Tue Feb 21, 2006 7:09 am

Here's what I know, someone correct me if I'm wrong:

CATIII refers only to ILS (Instrument Landing System). There are CATI, CATII, and CATIII ILSs, and the higher the number, the less stringent the weather requirements are (and the more stringent the equipment requirements are). CATIIIb allows landings with no visibility at all.

Airports are not CATIII certified, specific approaches are. In order to fly a CATII or III approach, the airplane and flight crew must also be certified. Most major airports are going to have either a CATII or CATIII ILS approach. For example, JFK has a CATIII approach to 4R and 22L (both ends of the same runway). The ILS to 13L is CATII, and the ILSs to 4L, 22R, 31L and 31R are all CATI. The smaller airports will not have a CATIII approach, as they only become useful when the visiblity is REALLY bad, and the expense isn't justified.

I don't know of any list of airports with CATIII approaches.

RNAV is a method of navigating while enroute, and can also be used for approaches (though with far less precision than even a CATI ILS, and thus RNAV approaches are more stringent with regards to weather requirements). There are several types of RNAV, including VOR Radial/DME (not sure of the technical term for this, but it basically takes two VORs, calculates where you are in relation to the two of them by measuring your bearing and distance from both, and uses that to plot a straight course to a position you set in, which will be defined as another bearing and distance from both of them), inertial navigation systems, or GPS. Basically, RNAV is anything that allows you to navigate accurately on any course of your choosing, as opposed to being restricted to tracking navaids.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
seanp11
Posts: 281
Joined: Tue Jan 10, 2006 6:16 am

RE: CAT III Navigation

Tue Feb 21, 2006 7:23 am

Quoting Mir (Reply 4):
CATIIIb allows landings with no visibility at all.

IIIb goes down to 150 feet rvr. IIIc is zero-zero, and is hardly ever used becuase it would be very hard to be able to vacate the runway and taxi to the gate after landing.
 
Mir
Posts: 19093
Joined: Mon Jan 05, 2004 3:55 am

RE: CAT III Navigation

Tue Feb 21, 2006 9:11 am

Quoting Seanp11 (Reply 5):
IIIb goes down to 150 feet rvr. IIIc is zero-zero,

Right you are. My mistake.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
SWISSER
Posts: 1568
Joined: Sat Feb 12, 2005 11:31 am

RE: CAT III Navigation

Tue Feb 21, 2006 2:07 pm

Quoting Mir (Reply 4):
I don't know of any list of airports with CATIII approaches.

You can find it on the approach plates of the airports.
CAT III certified RWY's must have an APPR plate in addition to that and you must use it as a reference when CATIII minima are in use.

[Edited 2006-02-21 06:09:09]
What time is top of descent?
 
Mir
Posts: 19093
Joined: Mon Jan 05, 2004 3:55 am

RE: CAT III Navigation

Tue Feb 21, 2006 2:18 pm

Quoting SWISSER (Reply 7):
You can find it on the approach plates of the airports.
CAT III certified RWY's must have an APPR plate in addition to that and you must use it as a reference when CATIII minima are in use.

Oh, I knew that - I just don't know of any list of airports that have CATIII approaches (not in the US, at least). The only way I know of to find one is to look through the plates to see if there are any.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
PhilSquares
Posts: 3371
Joined: Sun Mar 28, 2004 6:06 pm

RE: CAT III Navigation

Tue Feb 21, 2006 5:00 pm

Quoting SWISSER (Reply 7):
You can find it on the approach plates of the airports.
CAT III certified RWY's must have an APPR plate in addition to that and you must use it as a reference when CATIII minima are in use.

In addition, the crew and the aircraft must be CAT III qualified.
Fly fast, live slow
 
IAHFLYR
Posts: 3943
Joined: Sat Jun 25, 2005 12:56 am

RE: CAT III Navigation

Wed Feb 22, 2006 12:21 am

Quoting GentFromAlaska (Thread starter):
I also saw a ref for RNAV made to RNP and also to Loran and Omega. RNP as I understand it newer which uses GPS technology whereas Loran dates back to 1960's and 1970's

RNP (required navigation performance) is the containment used for obstacle assesment and route containment based upon linear assesment rather than the older TERPS which uses an angular assesment. RNAV (RNP) approaches will have a very tight value associated with the procedures depending on airport issues such as runway centerline separation at airports that will use the approach in a independent/dependent senario to parallel runways or for obstacle clearance, so IAH may use an RNP .15 for that and say DFW use RNP .18 and so on. The way it's happening now crews will have to special authorization to fly the approaches from their POI's and the aircraft special certification much the same as a CAT II/III ILS's.
Any views shared are strictly my own and do not a represent those of any former employer.

Who is online

Users browsing this forum: No registered users and 19 guests