Category I-III ILS Approaches & DME Approaches

[US B767-201ER]

Hello,

I was wondering, what is the difference between a Category I, Category II, and Category III ILS approach? What characteristics from each classify it as a Category I, II, or III?

Also, how exactly is a DME approach performed during landing? I have not been able to find accurate information on this.

Thank you for your input.

US B767-201ER

[FatFlyer]

The DME is part of the ILS/DME approach allowing you to check your heights with distances from the threshold rather tham using marker beacons which flash and bleep as you pass them on the approach.
CAT 1 takes you down to a decision height of 200 feet, when if not visual you should go around. CAT 11 takes you down to between 100 and 200 feet and CAT 111 to a decision height of below 100 feet or no decision height.
CAt 111 is sub divided into A,B and C depending on the vis required and whether it provides centreline tracking for the autoland. I can't remember the figures for the vis required for each category though i think it's 550 metres for CAT 1 going down to about 150 for cat 111. please correct me if wrong.

[DBate]

Landing Minima (applicable in DH - RVR):

CAT1: 200' - 550m (1800ft)
CAT2: 100' - 300m (1000ft)
CAT3a: 50' - 200m (700ft)
CAT3b: DH depending on AC type - 125m (400ft)
CAT3b: may go down to 0' - 75m (if AC certified for this minimum)

So long, DBate

[US B767-201ER]

Thanks for the info. I greatly appreciate it!

US B767-201ER

[square leg]

Some operators or for that matter A/C are certified to go down to 50' with 150 m RVR for CATIIIa approaches. The Avro Rj (BAe) can do just that.

They can do it on 3 engines as quite correctly pointed out. That would in fact be the MKII Avro's. The MKI's can land on 3 engines as well, but are simply not certified to do so - talking about CATIIIa (autolands) that is.

[FlyboyUK]

Yes that's right, and the RJ100 can do it on 3 engines!

[POL.777]

BAe = Bring another engine:ok:

have a nice weekend.

bst rgds

POL