30

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 amplitude modulation depth? Your question is very relevant, it can arise naturally if you happen to look at web pages using half correct descriptions (for ...


8

Conceivably the I-ETI DME transponder could be out of service, preventing you from identifying YOCUB (unless you have a second VOR or GPS), but you could still identify BASSO on the CHS DME for the missed.


8

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), they are not recognized as the appropriate standard of vertical guidance required for an ILS approach. Many airports that have an ILS also have LOC (localizer-...


8

Adding to @J.Hougaard's practical reasons, there is one technical reason in the existing standards I can think of: The identification signal (morse code) is provided by the localizer, not the G/S, so G/S-only approaches would be unidentifiable. (ICAO Annex 10 Vol 1 § 3.1.3.9) Side note: I'm not sure if there can be a workaround for it using existing ...


7

For the same reason the basic answer is no to the question "Can two opposite localizers to a single runway be on simultaneously?" The installation will be more expensive than the additional antennas due to the extra validation required to ensure that there is no signal interference. Not to mention a curved path approach typically means there is high terrain ...


7

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 advantages of RNP include accuracy and integrity monitoring, which provide more precision and lower minimums than conventional RNAV. RNP DAs can be as low as 250 ...


7

Looking at the charts, I can see quite a few good reasons for not providing glideslope for the West approach: The East approach leads you (almost) directly to the runway threshold, the West approach leads you a few miles east of the airport. The East approach has more terrain clearance. If you go only slightly below the glideslope for the West approach, you ...


7

Because there would be no benefit to doing so. where the pilot uses the glideslope for vertical guidance but relies on ground- or satellite-based navigation fixes for lateral guidance. As you correctly point out, if using only a glideslope, the pilot would have to rely on other navigation facilities for the horizontal guidance, for example a locator/NDB ...


6

The localizer for runway 09 is offset by 3°, almost certainly because of terrain. That would be a typical reason for a non-standard installation. The approach plate for the LOC RWY 09 approach notes the offset (more than 3° and it would be an LDA approach): The final approach course for the LOC 09 is 093°, whereas for the two RNAV (GPS) approaches it's 096°...


5

Any VHF radio can receive the carrier signal of a LOC signal but to use it, you need dedicated circuitry. The LOC transmitter transmits the carrier wave, frequency modulated with two side lobes of 90Hz and 150Hz. In order to use the LOC signal, circuitry needs to exist which will filter out the 90 and 150Hz then measure the difference between them to ...


5

Notice that in the plan view, the shading of the localizers are on the opposite sides. If you are flying south-west, the actual localizer used for the approach has the shading on the right, while the one used for the missed approach has the shading on the left. This can also be used to tell you what sensing to expect. The note is also there to make it more ...


5

The approach shows that the glideslope (if it were working) is a three degree descent angle. You can calculate your own visual descent point (VDP), since one isn't provided for you, by taking the height above touchdown (600 ft. in this case) and dividing it by 300 ft/NM. This gives you 2.0 miles from the runway. Since the chart shows the runway threshold ...


4

The maximum angular offset for a LOC is 3° for FAA and 5° for ICAO. Everything else is named either LDA (FAA) or IGS (ICAO). In ICAO wording, any ILS which doesn't meet all ILS requirements is an instrument guidance system (IGS). Localizer type directional aid (LDA) is a designation used by FAA. Guidance /aid refers to the fact that this system is not a ...


4

A VNAV with localiser approach is normally a backup to a regular ILS should there be a glide slope unserviceability. The use of VNAV to manage the vertical portion of the approach would allow the use of APV minima which are normally lower than using a vertical speed mode. VNAV is a better mode when conducting non-precision approaches as the aircraft is ...


4

The 620 is not at WESTS. It's been discussed in multiple places, e.g.: https://mooneyspace.com/topic/19113-ifr-fix-minimums-question-kipj/ https://www.pilotsofamerica.com/community/threads/fix-minimums.28308/ The way to read it is [WESTS FIX] MINIMUMS, and not [WESTS] FIX MINIMUMS, i.e., the 620 is not at WESTS, but the 620 is when you can identify WESTS (...


4

The frequencies are chosen to allow the system to produce a localizer and glideslope 'beam' that provides proportional guidance that can adequately guide an aircraft on the approach. Read through this Question and Answer. As you can see in the description of the beam-forming, the width of the antenna array and the choice of the modulation signals (90 ...


3

An AC motor in the USA will turn at 60 RPM and 90 is 3/2 and 150 is 5/2 of 60. Both can be generated using a simple gear drive which would reduce the costs during development. Similarly there are circuits to multiply or divide a driving frequency by whole numbers, with 60 hertz readily obtained. Simple gear ratios could convert 50 hertz used elsewhere. 90 ...


3

You have a few different points here but the short version is: IWA is a VORTAC and I-IWA is a localizer, i.e. they're different navaids. DME is available from IWA and it's optional but not required for the I-IWA localizer approach. If you do have it, you can use it to identify the ORIYE fix and use the lower minimums at the bottom of the plate, e.g. 1800-1 ...


3

It's all laid out in Order 8200.1D United States Standard Flight Inspection Manual. That and other documentation, including the inspection reports can be found from the FAA website under Flight Inspection Information.


3

Yes. Usually, shutting down the ILS means shutting down the localizer and glideslope signals. There is more than one reason to 'shut down' the ILS. The ILS is designed to shut down automatically on detection of fault. FOr example, if the primary transmitter (of glideslope) malfunctions, the system will automatically transfer to the standby transmitter. If ...


3

The ILS, or precisely the components localizer and glidepath antennas can be shut off, as they are electronic devices that emit radio signals. They can be turned off and on by ATC where required, e.g. having the same ILS frequency for two opposite runways and you only want one to be active at the same time or they can be shut down by maintenance directly at ...


2

Ignore the 1919 glideslope intercept at the OM, as that is for an ILS approach only. For the LOC approach, in Cat A, you will cross the FAF at 2000 and descend to the 660ft MDA over the next 5.5nm. There are (at least) two ways to plan and fly a non precision approach. You can just try to descend constant from the FAF to the MAP, hoping you reach the MDA ...


2

Mod Depth (more commonly called modulation index in electrical engineering) is the amount a carrier signal is modulated. Mod depth has nothing to do with antenna configuration and is set by the transmitter (or more precisely the modulator). The log periodic antenna controls the width of the various beams. A larger antenna means a smaller beam and smaller ...


2

Well, I’m not an FAA guy so I can’t find the relevant FAR quote, but going more general: ICAO Doc 8161 Vol 1 - Aircraft Operations I-4-6-1 6.1.4 Note 2 In the case of a missed approach with a turn at an altitude/height, when an operational need exists, an additional protection is provided for the safeguarding of early turns. When it is not possible, a ...


2

No, you can go missed anytime you feel you cannot complete the approach you are currently flying successfully. This includes anytime you are flying the final approach segment before reaching the VDP, if there is one, and all the way to the MAP at MDA. A failure of a required piece of equipment needed to fly the approach properly would be a mandatory reason ...


2

Even if it were technically possible to have a multisegment ILS approach, the economics just don't make sense. Each ILS costs millions to install and millions more to keep running properly over its lifetime. You need a lot of traffic to justify that cost. Now multiply that by however many segments you need, and then consider whether an airport that hard to ...


2

Let's consider the ILS on its own, with no supplement navigation aids like RNAV / GPS. Assume IFR conditions. A LOC+GS approach can get you onto the runway. A LOC-only approach simply won't work, you need at least one more piece of information, e.g. DME. A LOC+DME approach would be similar to a VOR+DME approach. You'd step down your altitude as your DME ...


1

On Question 2: If there is a functioning DME on the airplane, and there was a DME signal that could be used, that is, a DME at the localizer or a DME at a VOR that is aligned with the approach path, yes you could use that, but it almost certainly the approach itself would be a VOR/DME approach and you would be using DME as primary anyway, with timing as a ...


1

From the book "Principles of Avionics" By Albert Helfrick: The amount of modulation is twice that found in the localizer. Because the glide slope does not have ident or speech audio, the percentage modulation for 90 and 150 Hz tones is increased.


1

When ILS was developed, they actually used rotating capacitive plates with lobes. The 90 had 3 lobes and the 150 had 5. Easy way to modulate the RF with the phases locked. The depth of modulation was adjusted with a fixed plate with a variable gap between it and the rotating plate.


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