View Full Version : What is an IGS approach?


Grum
29th Nov 2006, 14:46
Should be a simple question for someone. Going into Sion (LSGS) this weekend and it has an IGS not an ILS. I've seen this somewhere before but can't remember where. Is it to do with the steepness of the approach only or is the actual equipment different from a standard ILS. I take it standard ILS receivers on the aircraft can receive the IGS.

Anyone know?



mcgoo
29th Nov 2006, 15:11
iirc its an instrument guidance system, a modified ILS, and it used to be used for the marker board at the Kai Tak approach to runway 13, someone else may have more details

Rainboe
29th Nov 2006, 15:13
I think it just means an ILS system that for various reasons does not take you right down to the runway for landing, but you have to break off and complete a visual landing. This is when the localiser is significantly misaligned with the runway for terrain reasons, or presumably the GS is also affected. As far as I am aware, the signals are just normal ILS transmissions.

BOAC
29th Nov 2006, 16:01
Looking at the charts, it is 'standard' ILS type, but at a 6 degree angle. It is not lined up with the runway and requires visual manoeuvring for landing as said above. Innsbruck has an approach (from the west) which has no glidepath (and passes well south of the airport, for visual manoeuvring) and is thus called a Localiser/DME approach. I assume it is the presence of a glidepath at Sion that produces this terminology.

There are, doubtless, experienced Sion operators here (not sure I want to be one:) ) who can give you the full story.

JackOffallTrades
1st Dec 2006, 00:02
IGS - Instrument Guidance System at Sion takes you to a point where you can position visually to land. I seem to recall the one at Innsbruck takes you to a hospital car park!!? Convenient!!! The IGS at Sion is called an IGS because it doesn't terminate at the runway. Approaching 26 you will need to reduce your rod at minimums and maneuver posistively around the ridge to line yourself up.

Having been to Sion several times in a BAE RJ100 I'd recommend becoming totally au fait with the visual procedures, the shape of the Rhone valley around the field and procedures to follow if you go IMC inadvertantly.

Best advice I can offer is obtain a weather report (actual and forecast) from the tower there. The local knowledge of weather conditions of the guys in the tower there is excellent.

Good luck.

P.s. They also have arrester cables if things go really bad!! ;)

Grum
3rd Dec 2006, 13:28
That all seems to make sense. It certainly doesn't take you to the runway. The instrument approach ends at 3000 feet above field elevation and for the likes of me who has not completed the authourisation course, i have to initiate MAP at 5000 feet agl.

have been in twice now and it is stunningly beautiful in clear and sunny conditions. I have practised the IGS and just hope that i don't have to rely on it anytime soon.

Are there certain types of aircraft which could not descend on a 6 degree slope with less than 200kts on the clock? Would a citation or the likes have to take full flap and gear at the top of the slope or would you use speed brakes all the way down? I see FLYBE come in here, what do they use, Dash 8 and if so what procedures do you use in terms of configuration and speed? Just interested if anyone in the know is watching. :rolleyes: