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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
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37 votes
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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
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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
18 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
  • 181
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
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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
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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
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15 votes
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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
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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
  • 55.4k
13 votes

When do pilots disconnect the autopilot on an ILS approach?

The decision to disconnect the autopilot is made by the pilot and can be made at any point as long as the operational limitations of the aircraft are satisfied (according to the type of ILS). The ...
aeroalias's user avatar
  • 100k
13 votes

What makes a visual approach quicker than an ILS approach?

Visual approaches can be conducted from any point around the airport where the runway is in sight, e.g. if you are approaching from the north of the airport, you can be vectored to a position which is ...
SentryRaven's user avatar
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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
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What is the difference between "Land 2" and "Land 3" annunciations for Boeing autopilot systems?

From "Smart Cockpit" B777 Automatic Flight (PDF!) AFDS Status Annunciation The following AFDS status annunciations are displayed just above the PFD attitude display: • FLT DIR (the flight ...
Mike Sowsun's user avatar
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11 votes
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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
  • 14.8k
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
Accepted

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

The "A" is not an inner marker. The A is an airway marker. Airway markers were part of a now-obsolete system of "red" airways. They were placed along the enroute path and they could be picked up at ...
TomMcW's user avatar
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10 votes
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Does ATC provide ILS frequency and course setting for the runway in use?

When nearing their destination, pilots will be checking weather and airport information. This will let them know which runways are being used for landings and what type of approaches are being used. ...
fooot's user avatar
  • 72.8k
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
Accepted

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

When do pilots disconnect the autopilot on an ILS approach?

I am a B777 pilot; on approach I typically disconnect the Autopilot once visual contact is assured and I am inside the Final Approach fix. If there is any chance of a possible missed approach, (...
Mike Sowsun's user avatar
  • 37.7k
9 votes

What makes a visual approach quicker than an ILS approach?

At the risk of just repeating information from the great answers that SentryRaven and casey already gave, here's a real example. Last night I flew the ILS 22 into KLEX for practice, although ...
Pondlife's user avatar
  • 71.7k
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
  • 17.7k

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