ILS Approach

ILS is a system designed to aid pilots for executing landing in IFR environment, particularly under low visibility. The predecessor of ILS was PAR (Precision Approach Radar) system which uses a narrowband radar to guide the landing. The two systems are pretty similar to each other except PAR requires a dedicated operator to monitor the radar in the tower and issue verbal instructions to advise the landing aircraft for any correction. In constrast, ILS interpretate the information into graphics and presents on the instruments onboard the aircraft. This allows pilots to receive the approach information without delay, which's essential to today's civil aviation.

ILS consists of two components, namely 'Glideslope' and 'Localiser'. The glideslope is for vertical positioning while the localiser is for horizontal positioning. Imagine that an aircraft is approaching the airport and it needs to change the course in order to align with the centreline of the runway it intends to land on, while at the same time it's descending from a certain height.

The glideslope is used to guide the approaching angle of the aircraft. It's very important as a steep slope may result in landing too fast, whilst a shallow slope may cause the plane to fly too slow and lead to stalling. A good glideslope also allows the pilots to have adequate visibility to the runway. Hence the glideslope is literally a compromise between the vision of the pilot and the approach speed of the aircraft.

The localiser is used to guide the alignment of the landing aircraft with the runway. Imagine that you're 20miles away from the runway. You can't really tell whether you're aligned with the runway as it appears to be too small to tell. Here the localiser comes in to help pilots to fly in straightly.

Some ILS also incorporates a device called PAPI, or Precision Approach Path Indicator, which is installed next to the threshold of a runway. It gives out light signals to the landing aircraft to indicate whether its glideslope's too steep or too shallow. The task's carried out by 4 lights. When you see 4 whites you're flying too high. When you see 4 reds you're flying too low. If you see 2 white and 2 red you're right on the glideslope.

It's pretty difficult the explain it without the use of pictures. Fortunately there's an article discussing the ILS system in MS Flight Sim where you'll get the information regarding how to use it.

The instrument landing system is a method of guiding a pilot through the overcast to a landing by means of visual reference to instruments in the cockpit. The system provides alignment and descent information about the approach path of the aircraft as it descends towards the runway. The system consists of a localizer, a glide path transmitter and a non-directional beacon (NDB) along the approach path. A DME fix may replace the NDB in certain installations.

The localizer transmits a radio beam whose purpose is to keep the pilot lined up with the centreline of the runway. The localizer transmitter is located at the far end of the runway and operates in the VHF band.

The glide path beam guides the aircraft along the proper downward appoarch path to enable it to touch down on the threshold of the runway. The glide path transmitter is situated about 1000 feet from the appoarch end of the runway and is offset about 400 feet from the runway centreline. It operates in the UHF frequency.

I don't think i can answer ur question just simple.

i learn the instrument rating and it needs at least 2-3 weeks.

if u just want that to play the Flight simulator, u can learn it in the lesson of fsx.

or just simple to do following things :

when u are approach the airport u want to land, use the world map, click the + / - button and side to go to the airport, click on it, it will shown the airport frequency , location........
find the runway u want to land.
then copy down the ILS LOC Frequency and the course heading (thus runway heading)
then return to cockpit, set those freq and course heading. ( NAV 1 and course)
turn on FD
turn heading to aiport and the heading is within 40 degree to the runway heading.

when the DME on , change the NAV / GPS to NAV
turn on autopilot, landing config, keep alt
turn on nav heading (autopilot)
the plane will auto go to the runway
when the glidescope (the hoz side bar at ur ati indicator ) come from up to center
turn the APP on
then the plane will auto land to runway

HOPE this will help u find the funs.

其實你所問o既問題olgacarol2003已經答得好清楚；以吓我自己o既網誌有提及Localizer, Guide Path 同 PAPI o既圖片同簡介。

PAPI
http://hk.myblog.yahoo.com/jw!KNvV2tGBFRQL_dl7ZDZj1_gx36b6/article?mid=813
目視輔助的降落系統中，最廣為人知的有VASI, T-VASI及PAPI；其中又以PAPI - Precision Approach Path Indicator最廣泛被世界各地的機場使用，就連香港和澳門國際機場也是沿用這套系統作為目視降落的輔助儀器。系統通過白色和紅色的燈號，令機師可清楚地知道自己的降落角度是偏高、偏低還是正確。

由像四個燈箱一樣組成的PAPI，其實每一個燈箱內各有三盞燈組成。因此，假若有燈有故障熄滅了，也不致於影響到整個系統的運作。

PAPI以五種不同的形式讓機師知道現處的降落角度如何：

1. 由跑道內向外觀看，兩紅兩白的燈號代表下降角度正確。
2. 由跑道內向外觀看，三紅一白的燈號代表下降角度偏低。
3. 由跑道內向外觀看，四燈皆紅代表下降角度過低。
4. 由跑道內向外觀看，一紅三白的燈號代表下降角度偏高。
5. 由跑道內向外觀看，四燈皆白代表下降角度過高。

ILS
http://hk.myblog.yahoo.com/jw!KNvV2tGBFRQL_dl7ZDZj1_gx36b6/article?mid=252

Localizer：能發出令飛機能正確對著跑道中線著陸的訊息。

Glide Path：能發出令飛機知道正確著陸角度的訊息。

當然，上述兩項只是導航儀器的其中一部份。不過，亦是不可或決的一個重要元素啊！

www.wikipedia.org