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39 votes
Accepted

Was it possible to land a Boeing 707 with 300 feet cloud ceiling in the 70s?

ILS approaches were in common use in 1970 when I got my instrument rating. The normal (Cat I) ceiling minimum was 200 feet. So, yes, a 707 would have been able to land with a 300 foot cloud ceiling in ...
Terry's user avatar
  • 39.2k
39 votes
Accepted

How is varying modulation depth achieved by localizer ground transmitters?

The beam strength decreases as you move away from it's own centreline, so is it actually that the entire modulated signal strength decreases which when de-modulated is effectively a difference in ...
mins's user avatar
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35 votes
Accepted

Does a portable ILS ground station exist?

NASA did some research on it in 1986 and published this paper. Thales was contracted to build one that the US Army has ordered and it made it to prototype phase. Eventually it was tested for a while ...
Dave's user avatar
  • 101k
20 votes
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What is the purpose of having different ILS categories?

Instrument landing system - ILS - is a very common precision approach system used in airports around the world. An ILS consists of two ground antennas and an airborne received in the aircraft. One of ...
60levelchange's user avatar
20 votes

Why would the USAF have no support for autolanding?

I was a Flight Test Engineer on DC-10-10 Ship 2 which was the Avionics Test airplane during initial certification. The DC-10 airplane was certified to CAT III Approach and Landing. The KC-10A was ...
Gunn's user avatar
  • 201
18 votes

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

No, the directional part of ILS is located at the ground. (Ground) transmitter creates lobes with specified frequency and modulation to mark the high, low, right and left areas. LOC and GS signals ...
Martin's user avatar
  • 2,766
17 votes

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

A point shown in parentheses like this is called a Computer Navigation Fix (CNF). If it didn't fall right at the end of the runway, it would be marked with a small X. It's defined in the legend on ...
fooot's user avatar
  • 73.4k
16 votes
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How does a pilot select the correct ILS when the airport has parallel runways?

The two ILS approaches on parallel runways will have a different ILS Localizer frequency. The pilots will select the correct approach from the charts and then either manually tune in the correct ...
Bianfable's user avatar
  • 56.4k
15 votes
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Is it true an ILS CAT IIIc can automatically taxi-in an aircraft?

There is no provision in the ILS system to provide for an auto-taxi or runway vacate. IIIc is just zero-zero and roll-out control, not auto-vacate as the linked AvWeb article seems to suggest. Its a ...
Ron Beyer's user avatar
  • 36.2k
15 votes
Accepted

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

Listen to the identifier... That will tell you if you have the 10R I-MRY or the 28L I-MTB ils. Some runways use the same frequency like this, while others use different frequencies for opposite ...
Ralph J's user avatar
  • 51.8k
14 votes

Is there a list of airports with Category 3 ILS systems?

According to my current navigation database (AIRAC 1912), the following 228 airports have a category III ILS approach to at least one of their runways: ...
Bianfable's user avatar
  • 56.4k
12 votes
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What is the maximum interception angle for ILS when on radar vectoring?

45 degrees. 8.9.3.6 Aircraft vectored for final approach should be given a heading or a series of headings calculated to close with the final approach track. The final vector shall enable the ...
60levelchange's user avatar
12 votes
Accepted

Why wouldn't KJFK offer the ILS for 22L?

JFK ARR ILS 22L/22R DEP 22R If conditions dictate the use of JFK ILS RWY 22L approach, then (1) the JFK Area owns Belmont airspace 3,000' and below, (2) releases Coney airspace to LGA and LIB, (3) ...
Michael McCracken's user avatar
12 votes

Do any aircraft have a "self-contained ILS"?

Approaches guided by GPS are called RNAV; it can provide both lateral and vertical guidance, in some cases to the same precision as ILS Cat I, without need for a radar altimeter--which is not standard ...
StephenS's user avatar
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11 votes
Accepted

Why is an approach that relies on both LOC and PAPI not considered a precision approach?

I think you're overlooking the primary reason pilots fly instrument approaches: the conditions do not permit flight by visual reference. The fact that a PAPI provides vertical guidance is more or ...
egid's user avatar
  • 23.3k
11 votes

How much obstacle clearance is provided within full scale deflection below glide slope on ILS?

In the USA, FAA Order 8260.3 specifies the Standard for Terminal Instrument Procedures. The defining concept of terminal procedures is the Required Obstacle Clearance (ROC) between the nominal flight ...
randomhead's user avatar
  • 15.6k
10 votes

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

The other issue with ILS Cat IIIc not being operational is the inability of the ground support systems to function in zero visibility. So, in case an aircraft requires assistance (fire for example), ...
ashok varma's user avatar
10 votes

Do any aircraft have a "self-contained ILS"?

You don't need nearly all the equipment you mention. A great deal of aircraft are capable of flying GPS/RNAV approaches from big boys down to the little Piper Archer I fly. Units as small as a Garmin ...
Dave's user avatar
  • 101k
10 votes
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What does ''NAV ILS OUT OF SERVICE'' mean?

It means exactly what it says. The ILS is out of service, so you can't use it. An ILS can consist of several different elements, for example localizer, glidepath, DME, inner/middle/outer markers as ...
60levelchange's user avatar
9 votes

Why would a PAPI and ILS glide slope for the same runway not coincide?

From the FAA AIM (section 2-1-2(b) Visual Glideslope Indicators): PAPI angles are based on obstruction clearance +/- 10 degrees from the runway centerline, up to 4 miles from the threshold. The ILS ...
hashinclude's user avatar
9 votes

Could a terrorist hack the ILS?

There are numerous unclassified papers talking about LOC, GS, MLS and other navaid jamming. There are also instances of that happening, both intentionally and unintentionally. The issue with consumer ...
mongo's user avatar
  • 17.8k
9 votes

Can I do a CAT III ILS approach if minimums are above CAT I?

Yes, you can request it. We (ATC) may or may not grant it. It can be quite complicated for us to establish CAT II/III procedures, including having to switch over to backup power, turning on stopbars ...
60levelchange's user avatar
9 votes
Accepted

Do different planes (category) aim differently in the 'final stages before flaring'?

Because of the downrange offset between the PAPI and the GS antenna, only a P3 (jumbo jet size) PAPI (14 meters eye to wheels) gives a more or less parallel path between the ILS glide slope and the ...
John K's user avatar
  • 132k
8 votes
Accepted

Can I make an ILS-Approach when I am VFR?

Sure you can. Just request to fly the approach using either radar vectors or initial approach fixes, if available. The tower will usually comply and grant you the approach clearance, adding "...
Romeo_4808N's user avatar
  • 74.1k
8 votes

Why are the minimums between these two ILS instrument approaches to the same runway so different?

The equipment requirement (in the aircraft) are different for each of these approaches. In the upper-left box of the Z approach, you can see that DME is required to make this approach. This ...
Jimmy's user avatar
  • 2,859
8 votes

Can two opposite localizers to a single runway be on simultaneously?

ICAO Annex 10 Volume 1 has the answer: 3.1.2.7 At those locations where two separate ILS facilities serve opposite ends of a single runway, an interlock shall ensure that only the localizer serving ...
60levelchange's user avatar
8 votes

Can I execute an ILS approach using a NAV CDI with LOC signal only?

No, you cannot execute an ILS approach without an ILS glide slope indication as the primary form of vertical guidance. Even if you could supplement it with alternatives (WAAS, GPS software, etc), ...
Ryan Mortensen's user avatar
8 votes
Accepted

What prevents the use of a multi-segment ILS for non-straight approaches?

See here, pages 5-23, 5-24. Things have advanced well beyond ILS for that kind of approach. https://whispertrack.com/pdf/faa_handbook.pdf REQUIRED NAVIGATION PERFORMANCE The operational ...
CrossRoads's user avatar
  • 8,795

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