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 ...
- 39.1k
35
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 ...
- 69.7k
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 ...
- 100k
21
votes
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Can the ILS glideslope be intercepted from above?
Assuming that you're asking about intercepting the glideslope from above rather than the localizer, the answer is that it is definitely NOT recommended.
There are at least two significant problems if ...
- 39.1k
19
votes
Accepted
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 ...
- 35.7k
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 ...
- 2,469
17
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 ...
- 171
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 ...
- 71.8k
16
votes
Accepted
What's the point of having ILS on runway signs?
These markings designate the hold-short point during different runway operations.
Runway hold-short points are marked by white text on a red background. They designate a point which any aircraft must ...
- 39.6k
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 ...
- 53.5k
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 ...
- 48.5k
15
votes
Accepted
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 ...
- 36k
14
votes
Accepted
What is different between a Cat IIIA, Cat IIIB, and Cat IIIC ILS approach?
ICAO and FAA CAT III definitions
A CAT III operation is a precision approach at lower than CAT II minima. Sub-categories are listed below.
A category III A approach is a precision instrument ...
- 1,058
14
votes
Accepted
Is it possible for more than one airplane intercept the ILS at the same time?
Yes, since the ILS is just a set of radio signals emitted and received by aircraft, there can be more than one aircraft established on localizer and glidepath. The ILS does not lock or tune onto one ...
- 15.6k
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:
...
- 53.5k
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 ...
- 99.8k
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 ...
- 15.6k
12
votes
Accepted
Why haven't helicopter CAT III procedures ever been developed?
Because many copter autopilots are capable of flying a Cat I ILS to 200AGL, and then descending on autopilot into a hover at a pre-determined altitude above the runway. The pilot can then descend down ...
- 16.7k
12
votes
Accepted
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 ...
- 35.7k
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) ...
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 ...
- 27.6k
12
votes
Accepted
What should I do if I intercept the glideslope before reaching the final approach fix?
JERIT is the FAF for the LOC approach, as indicated by the Maltese cross.
However, the FAF for the ILS approach is not JERIT; it is the Glide Slope Intercept Point (at 2000 ft indicated altitude) ...
- 32.4k
12
votes
Accepted
What do the "GP 330.5" and "CH24X" I marked in the picture below mean?
24X is the paired TACAN channel. It's paired (permanently associated) with 108.7 MHz (localizer frequency for LTAF) and 330.5 MHz (Glide Slope). See this reference. (Scroll down to see the table)
So, ...
- 32.4k
11
votes
Accepted
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 ...
- 37.3k
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 ...
- 23.2k
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 ...
- 13.2k
10
votes
Accepted
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. ...
- 71.8k
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 ...
- 28.3k
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), ...
- 101
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 ...
- 100k
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