brodiebrazil
Posts: 86
Joined: Tue Nov 18, 2003 12:56 pm

Can somebody explain to me what the Localizer is all about?

Mon Jan 19, 2004 4:42 pm

Can somebody explain to me what the Localizer is all about. I hear a lot about intercepting it, but am not quite certain what how it helps on the approach.

I apologize in advance for such a basic question.
I say thanks in advance to anyone for helping me!
 
saintsman
Posts: 2037
Joined: Fri Mar 15, 2002 12:34 am

Can somebody explain to me what the Localizer is all about?

Mon Jan 19, 2004 4:55 pm

Very simply, its a system used for lining an aircraft up onto the runway heading (particularly useful if you can't see the runway. It uses a radio signal which when interprated by the aircraft, tells it to fly either left or right. This can be a visual indication or coupled to the autoplilot and flown automatically. Once the aircraft is established on the runway heading (no fly left or fly right signal) the aircraft flys towards the runway until it meets the glideslope, which gives the aircraft fly up or down signals, so that it can then come into land.
 
jhooper
Posts: 5560
Joined: Thu Dec 13, 2001 8:27 pm

Can somebody explain to me what the Localizer is all about?

Mon Jan 19, 2004 5:10 pm

No problem; that's how we all learn, isn't it. Anyway, if you have a AIM handy, you can read about it. Also the FAA's "Instrument Flying Handbook" goes into detail on the subject.

Just a couple of points to add to the above, if you have a glideslope associated with the localizer, you have what's called an Instrument Landing System (ILS) approach, which is also a "precision" approach. A localizer only approach (non-precision approach) does not have glideslope guidance. Only certain runways at certain airports have localizer approaches. If you go to a local FBO and purchase the "U.S. Terminal Procedures" for your area, you can see what instrument approaches are available near you.
Last year 1,944 New Yorkers saw something and said something.
 
brodiebrazil
Posts: 86
Joined: Tue Nov 18, 2003 12:56 pm

Can somebody explain to me what the Localizer is all about?

Mon Jan 19, 2004 6:01 pm

Thanks J...

One more question...

at what distance can the plane lock onto the localizer? then is it up to the pilot to intercept the glideslope, and when does that switch from heading to glideslope take place?

hope that makes sense.

thx
 
FredT
Posts: 2166
Joined: Thu Feb 07, 2002 9:51 pm

Can somebody explain to me what the Localizer is all about?

Mon Jan 19, 2004 7:05 pm

BB,
you intercept the localizer at a given altitude, the maintain that altitude until the glideslope "comes alive". Then, you remain on the localizer for left and right guidance while the glideslope tells you if you are high or low.

Both are essentially the same thing, just aligned at 90 degrees to each other. The localizer (LLZ) will tell you if you are left or right of the extended runway centreline* while the glideslope (GS) will tell you if you are above or below a nominal glideslope.

Cheers,
Fred

*There are localizers which are not aligned with the runway, offset localizers. There are even complete LLZ/GS combinations which lead you to an off-airport spot, intended to get you safely to a point where you can continue the approach using other means. In those cases, they are not considered ILS systems though.
I thought I was doing good trying to avoid those airport hotels... and look at me now.
 
jhooper
Posts: 5560
Joined: Thu Dec 13, 2001 8:27 pm

Can somebody explain to me what the Localizer is all about?

Tue Jan 20, 2004 1:07 am

Also, the glideslope is much more sensitive than a localizer. If I remember correctly, the localizer is 4X more sensitive than a VOR (enroute navigation facility), and the glideslope is 14X more sensitive than a VOR.

Also, I think the localizer is reliable up to a distance of 18 miles and 30 degrees of centerline.

These facts are from memory. It's been 6 years since I got my instrument rating so somebody please correct me if this is incorrect.
Last year 1,944 New Yorkers saw something and said something.

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