Cat ??? differences/requirements

[tightturnaround]

As a newcomer...I'd be grateful if somebody with the knowledge can summarise he differences in Cat standards...and what equipment on board/airport infrastructure is required for them. IE what is cat 1 and what is required for it aircraft/airport - wise..what is cat 2..and so on. This would help me greatly in a current project.

Thanks in advance guys.

[Checkboard]

I assume you are asking about different approach weather minimum standards. These different standards are only quoted for precision approaches - i.e. an ILS (Instrument Landing System). The ILS basically consists of a pair of radio "beams" aligned with a runway - one (called the localizer) gives azimuth (left/right) guidance, while one gives glideslope (up/down) guidance onto the runway. Both "beams" are selected and displayed for the pilot using the same radio tuner in the cockpit.

The different categories differ slightly between the USA and ICAO (International Civil Aviation Organization.)

ILS CATEGORIES (ICAO) -[list=1] ILS Category I - An ILS approach procedure which provides for an approach to a decision height not lower than 200 feet (60m) and a visibility not less than 2400 feet (800m) or a runway visual range not less than 1800 feet (550m).

ILS Category II (Special authorization required) - An ILS approach procedure which provides for an approach to a decision height not lower than 200 feet (60m) but not lower than 100 feet (30m) and a runway visual range not less than 1200 feet (350m)

ILS Category III - (Special authorization required)[/list=a][list=a] IIIA - An ILS approach procedure which provides for an approach with either a decision height lower than 100 feet (30m) or with no decision height and with a runway visual range of not less than 700 feet (200m).
IIIB - An ILS approach procedure which provides for an approach with either a decision height lower than 50 feet (15m) or with no decision height and with a runway visual range of less than 700 feet (200m) but not less than 150 feet (50m).
IIIC - An ILS approach procedure which provides for an approach with no decision height and no runway visual range limitations.[/list=a]

For each category both the runway installation and the aircraft installation and the pilots have to meet the required standards. Whether it is worth the extra expense depends upon the frequency of traffic, and the local weather - for instance all ILS installations in Australia (even at the biggest airports) are Category I, the weather simply doesn't justify spending the money on higher category installations.

[ 15 October 2001: Message edited by: Checkboard ]

[NextLeftAndCallGround]

The UK CAA used to publish CAP 359 which explained things very clearly. I don't think you can buy it anymore (JAR-OPS superceeded it?) but you might be able to find it in the CAA library if you're passing by.