Questions tagged [ils]

An instrument landing system (ILS) is a ground-based instrument approach system that provides precision guidance to an aircraft approaching and landing on a runway.

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Instrument landing: why do all electronic devices need to be shut off?

A few days ago, I took a flight home. Towards the end of the journey, the captain asked us to shut down any electronic device that we had on board, including iPods, CD players, phones and so on, ...
Nicola Miotto's user avatar
32 votes
3 answers
12k views

What is the behavior of false glideslope signals?

I know that an ILS transmits not only the correct glideslope but also signals that can be interpreted as a false glide path. But I'm not familiar with the details of these erroneous indications. What ...
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27 votes
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How does ILS (Instrument landing system) work?

How does ILS (Instrument landing system) work? I know it provides guidance to the runway by two signals, one modulated at 90 Hz, the other at 150 Hz, but how the airplane lock on those signals? ...
Gabriel Brito's user avatar
24 votes
1 answer
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Was it possible to land a Boeing 707 with 300 feet cloud ceiling in the 70s?

In the movie Airplane! (1980), the main characters had to land a Boeing 707 in Chicago airport in low visibility. The dialog says the pilot "should be able to see the runway at 300 feet". Given the ...
kevin's user avatar
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21 votes
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How precise is an ILS (Instrument landing system)?

I read that an ILS is a precision approach system. It provides a final approach with precision in both horizontal and vertical guidance to the runways. But I don't know how precise it is because there ...
ielearner's user avatar
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21 votes
4 answers
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What is different between a Cat IIIA, Cat IIIB, and Cat IIIC ILS approach?

In terms of aircraft equipment, approach minimums, procedural differences, and anything else relevant, how do the 3 types of a Cat III ILS differ from one another?
Ralph J's user avatar
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17 votes
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Does a portable ILS ground station exist?

Does anyone know of a good example of a portable ILS ground station? I mean, it can be used for temporary airfields.
Peter's user avatar
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16 votes
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What is a monitored approach?

I've heard this term used to describe approaches into low weather (e.g. category 2 ILS), what is it? How is this different than an ILS approach?
casey's user avatar
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What is the purpose of having different ILS categories?

What is the difference between CAT I, II and III ILS approaches? I understand that the different categories are used in different weather, but what are the differences, exactly? Do flight crews have ...
Geocrafter's user avatar
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15 votes
3 answers
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Is it legal to land in bad visibility conditions without ILS?

Korean Air Flight 801 crashed during bad visibility conditions in Guam because the ILS was out of commission and the pilot thought it wasn't. My question though is why he even tried to land there in ...
flyingfisch's user avatar
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What are the differences between Cat I, Cat II, and Cat III as concerns aircraft requirements?

I understand that Cat I, II, and III ILS approaches have progressively smaller weather minimums. However, I am asking about the aircraft themselves. What are the differences between Cat levels as ...
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14 votes
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How is varying modulation depth achieved by localizer ground transmitters?

An approaching aircraft's navigation receiver uses the difference in depth of modulation between the 90Hz and 150Hz signals which are amplitude modulated onto an RF carrier (on a channel between ...
Andrew Davis's user avatar
13 votes
3 answers
21k views

When do pilots disconnect the autopilot on an ILS approach?

In clear weather, when do pilots disconnect the autopilot, if the plane is flying an ILS approach and the autopilot is in "approach" mode (tracking both localizer and glideslope)? Would the answer ...
Robin banks's user avatar
13 votes
1 answer
3k views

Why do double-ended ILS runway share the same frequency from both sides?

Let's find a runway where there are localizer-related procedures at both ends, e.g. KMRY: 110.7 for both ILS RWY 10R and LOC/DME RWY 28L KLAX: 108.5 for both ILS OR LOC RWY 06L and ILS OR LOC RWY ...
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12 votes
5 answers
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Why would the USAF have no support for autolanding?

One thing I noticed when reading through the KC-10 flight manual (see page 184 for the specific reference) is that the KC-10 lacks support for Category III operations, unlike its civil DC-10 brethren. ...
UnrecognizedFallingObject's user avatar
12 votes
2 answers
3k views

What is the correct name for this ILS Indicator?

What is the correct terminology for the name of the aircraft instrument that looks like this?
GPPK's user avatar
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12 votes
3 answers
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Is it possible for more than one airplane intercept the ILS at the same time?

I was watching a timelapse video yesterday of the approaches on a busy airport (I don't remember which one), and I saw that about 3 or 4 planes were lined up and descending at the same time (they were ...
Gabriel Brito's user avatar
12 votes
1 answer
2k views

Do non-towered airports commonly have ILS?

Is it common, uncommon or rare for a non-towered airport to have ILS (Instrument Landing System) runways? Can a non-towered airport have ILS?
CGCampbell's user avatar
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Why are sidestep ILS minima not used in EASA-land? (specific example: EGKK)

If you are not aware, London Gatwick (aka EGKK) has a setup with a primary air carrier runway and a backup runway immediately next to it, such that only one runway can be used at a time. The main ...
UnrecognizedFallingObject's user avatar
12 votes
1 answer
2k views

Are zero visibility landings a possibility for the future of commercial aviation?

Airports usually close or slow down activities in fog conditions, e.g. this seems to be a significant problem in winter at Delhi airport. Large commercial aircraft would be able to land with no ...
mins's user avatar
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Why would a PAPI and ILS glide slope for the same runway not coincide?

Some pilots are reporting the glide slope on our PAPI is not coinciding with the glide slope on our ILS even though FAA did a flight check of our PAPI's. Are there any reasons why a PAPI and ILS would ...
Almighty 's user avatar
11 votes
1 answer
17k views

What is the difference between "Land 2" and "Land 3" annunciations for Boeing autopilot systems?

Another question's answers refer to certain Boeing jets having the capability to annunciate "Land 2" and "Land 3" when flying a coupled ILS approach. What does each of these modes require, and allow, ...
Ralph J's user avatar
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11 votes
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How does an eILS improve throughput (for the A380)?

While researching where Heathrow's MLS approachs had gone, the only thing I could find is a topic on Heathrow's new eILS (enhanced ILS). As of the topic's date (Aug 2015) it seems eILS is only ...
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10 votes
2 answers
1k views

Why haven't helicopter CAT III procedures ever been developed?

Why is there no helicopter equivalent to air transport CAT III ILS? This PPrUNe thread discusses that some helicopter manufacturers have tested coupled approaches down to very low visibility minima (...
UnrecognizedFallingObject's user avatar
10 votes
2 answers
6k views

What is the maximum interception angle for ILS when on radar vectoring?

Some time ago when I was designing the approach radar module for the ATC simulator for HCAA, the spec was very clear that the limit had to be placed at 45 degrees. So I took it for granted and I didn'...
Stelios Adamantidis's user avatar
10 votes
1 answer
9k views

Precision Approach systems: Why is ILS used more frequently than PAR and MLS?

I have studied that the main three systems for performing Precision Approaches (PA) are the ILS (Instrumental Landing System), PAR (Precision Approach Radar) and MLS (Microwave Landing System). ...
Airman01's user avatar
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10 votes
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How much obstacle clearance is provided within full scale deflection below glide slope on ILS?

Basically the question in the title. The military has regulations that say to obey the localizer minimums if more than have scale deflection below glide slope, but for civilians how much obstacle ...
Name's user avatar
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2 answers
3k views

ILS Approach, when can you descend on the glide path?

The following quote is from G. Bristol’s book, Ace the Technical Piloting Interview: You can descend on the glide path when You have been cleared for the ILS procedure. You have captured the ...
tedioustortoise's user avatar
10 votes
1 answer
402 views

Why are different distances listed for the ILS and the LOC on this approach chart?

Maybe someone has an idea why are there two separate distance values (marked in blue) for ILS and LOC approaches?
Julious's user avatar
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Why would an ILS have a glide path angle less than the preferred 3°?

According to EASA the preferred Glide Path Angle is 3°: EASA Easy Access Rules - Page 22 - 4.1.2.1. There are some airports (e.g. Larnaca 2.75°) which are using a lower Glide Path Angle than 3°. Using ...
Pascal's user avatar
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9 votes
2 answers
4k views

How does a pilot select the correct ILS when the airport has parallel runways?

How do you not mess up ILS on parallel runways? There are many airports with ILS and parallel runways, how do you select which ILS for the runway you want? For example there are RWY 22L AND 22R and ...
Mamad's user avatar
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9 votes
3 answers
9k views

Is it true an ILS CAT IIIc can automatically taxi-in an aircraft?

I've always wondered how would the theoretical (since no airport/plane has it) ILS CAT IIIc guide the plane off the runway? I mean from the perspective of radio signals. What component in the ILS ...
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9 votes
1 answer
2k views

What is "(CFMCC)" on an ILS approach chart?

I'm studying the ILS or LOC RWY 3 approach chart for KMKC. I'm trying to figure out what "(CMFCC)" at the runway means. Is it a computer navigation aid?
Tracy's user avatar
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9 votes
3 answers
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What prevents the use of a multi-segment ILS for non-straight approaches?

An ILS, consisting of a localiser beam to provide lateral guidance (which can also be used on its own for a non-precision approach) and a glideslope beam to provide vertical guidance, is (currently) ...
Vikki's user avatar
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9 votes
1 answer
2k views

What's the point of having ILS on runway signs?

Runway signs show the ILS category next to the runway designation. But if you flew and didn't drive to the airport, you already know (hopefully). Either way, you are taking off, so you don't really ...
Stelios Adamantidis's user avatar
9 votes
2 answers
4k views

What should I do if I intercept the glideslope before reaching the final approach fix?

On several of the ILS and RNAV LPV approaches in my area (and notably the ones I expect for my checkride), I consistently intercept the GS at 0.1-0.2nm before the FAF. An example: I am flying at ...
StephenS's user avatar
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8 votes
3 answers
6k views

What makes a visual approach quicker than an ILS approach?

In the question What's the preferred approach for a passenger jet? it is mentioned that pilots prefer Visual Approaches over ILS Approaches, as they are a lot quicker. Why would a visual approach ...
Gavin Coates's user avatar
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8 votes
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Can the ILS glideslope be intercepted from above?

Is it recommended to intercept the ILS glideslope from above? Are there any special considerations like unstable approaches or GPWS warnings?
Eduardo Guilherme's user avatar
8 votes
2 answers
1k views

Why does this Garmin GMA340 have an Airway/Inner marker indicator?

On this Garmin GMA 340: the outer marker is blue and is designated O the middle mark is amber and is designated M the inner marker is white and is designated A and placed on the far left. I looked ...
jskypilot's user avatar
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8 votes
2 answers
820 views

How do preceding aircraft affect the ILS signals?

(airliners.net) Planes on approach in sequence to London Heathrow. When LVP is in effect, the ILS area is protected. I'm wondering, when there is a queue to a runway, how does the long queue affect ...
user avatar
8 votes
1 answer
3k views

Can a pilot use ILS when cleared for a visual approach?

When cleared for a visual approach, do airline pilots still use the localiser/glideslope or GPS or even the autopilot, or is it strictly a "visual" approach?
Charles Harnach's user avatar
8 votes
1 answer
3k views

How much does an ILS approach cost?

A statement in this question, asking how to pay fees for using the airport services, without being at the airport, inspires me to ask a question. Quote: (Yeah I know... you gotta pay for an ILS ...
Noah Krasser's user avatar
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7 votes
4 answers
2k views

If you were to fly an ILS in a knife edge would you receve GS and LOC be flipped?

because LOC and GS work the same way, if you were to fly one at 90 degrees bank would your information be displayed on the wrong indicators?
krob99's user avatar
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7 votes
2 answers
2k views

Could a terrorist hack the ILS?

I'm reading all these reasons why consumer electronics can't be on during takeoffs and landings and one specific reference that is made over and over again is the sensitivity of the ILS equipment. I ...
Jim Allen's user avatar
7 votes
2 answers
15k views

What is the difference between the ILS Critical Area and the ILS Sensitive Area?

What's the difference between the ILS Critical Area vs ILS Sensitive Area? I'm getting multiple conflicting opinions online. e.g. I can't decipher from this set of definitions how exactly they ...
curious_cat's user avatar
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7 votes
1 answer
521 views

What do the "GP 330.5" and "CH24X" I marked in the picture below mean?

What do the "GP 330.5" and "CH24X" I marked in the picture below mean? I think 330.5 is localizer independent glidepath frequency but I have no idea what CH24X means. Does anyone ...
pilot162's user avatar
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7 votes
2 answers
3k views

When and how do I align with the runway during an offset ILS approach?

In X-Plane 11, when landing an A330 on 04R at Nice (LFMN) on an ILS approach, the aircraft is brought perfectly to the end of the runway but because this is an offset ILS the aircraft is at about 2° ...
Dzseti's user avatar
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7 votes
2 answers
9k views

Which airports have ILS Cat IIIC?

Are there any airports with ILS working CATIIIC? What do the charts for this procedure look like? Is there a missed approach procedure?
Joz's user avatar
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7 votes
1 answer
350 views

What would a Category II ILS approach require that a Category III approach wouldn't?

According to @RalphJ's first comment on my earlier question about ILS approaches in an E-Jet sans pitch trim: Are you sure that Cat III approaches are allowed in that condition? Typically, Cat III ...
Vikki's user avatar
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7 votes
1 answer
21k views

What is a localiser back-course approach and how does it work?

What does back-course approach mean ? How much signal strength should the back lobe of ILS should have in order to trace it and commence landing. How common is this type of landing for a pilot. What ...
Huntkil's user avatar
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