What makes a good ILS?

[ACARS]

On a recent jumpseat flight from Dublin to Teeside, the pilot mentioned to me that the ILS at Teeside was 'not as good as others'.

My question is, how is this possible? I was always under the impression that an ILS is an ILS, fact and they don't differ. Is it to do with interference on that particular wavelength?

Excuse my lack of knowledge. I'm just a 10hr PPL who's curious.

[This message has been edited by ACARS (edited 02 September 2000).]

[This message has been edited by ACARS (edited 02 September 2000).]

[Checkboard]

The ILS is made up of two signals - a Localiser beam (LLZ) for azimuth (left and right guidance) and a Glide slope (GS) beam for slope (up and down) guidance. From memory the old Cat I standard was for the LLZ beam to be a set width in terms of angle form the transmitter, which is located at the far end of the runway. The new (?) or Cat II+ standard is for the beam to be a certain width at the threshold.

What this means is that on long runways the LLZ beam is narrower (read: harder to capture & fly) than on narrow runways. Some GS beams are also steeper than the standard 3° slope as well.

[HugMonster]

Some are also prone to unexpected dropouts, interference, reliability problems, plus a total lack of any decent background music that you can dance to... :)

[tailwinds]

Hope this site helps you. http://webeecs.ent.ohiou.edu/avn/ilsreports.html

[Roundout]

Good ILS for me is....start running the flaps just as the glide comes alive, intermediate setting (around 190-180) at glide intercept - thrust at idle of course - chuck the gear at the marker, then the rest of the boards - spool her up somewhere round a 1000' - now that's what I call a good ILS - pity they don't always work out like that (many memories of trying to hammer the levers back through the physical stop while the aircraft's making this wierd juddering noise).

[Tinstaafl]

Checkers,

I think it was the old, uncategorised ILS that was a single beam width (2.5 deg?), and all the categorised ILS installations that have beam width varied to give the same lateral displacement over the threshold for a given left/right indication.

[Slasher]

Who remembers the old 06 ILS at Manilas Ninnoy Aquino? Yo-yo glideslope all the way down and a LLZ that was more an airport locating device than an electronic precision runway guide. It was bad enough to fly even in good weather!

[Dan Winterland]

IMHO, it is all down to the location. It's all about where you are and what is at the aerial end of the ILS that counts. For example, McCarran in the USA is a good ILS, as Las Vegas is at the end. Hickam AFB is good, as Hawaii is what awaits. Not so good ones include Kinloss and Lajes. In the poor category, you have Al Kharj and Goose Bay. The worst ILS in the world though must be at Mount Pleasant Airport in the Falklands.

Does that answer it?