Minimal Range for ILS approaches?

[Yajvan]

hi guys, i was 50 nm away from KSEA and i entered the correct frequencies and the omnibearing selector. But, when i press "APP" its not going and lining up with the rwy. But, when i go near. it works. I dunno how this ILS works. pls help.

[mrzippy]

50 miles out is too far away to pick up a localizer. I usually don't even pick up the ILS Morse Code until about 28 miles out and the localizer at about 16 miles.

[Yajvan]

Ok thx but suddenly sometimes when i press APP it does not turn on. In the other case, it gets deactivated by itself.

[rfresh737]

You're not following airline standard practices for shooting an ILS. Pressing APP 50 miles out is incorrect to say the least. Visit my YouTube channel and there you'll find a playlist of how to fly the perfect ILS approach videos. Once you know how its done in the real world, you'll be amazed at how great your ILS approaches will be.

 

Specifically in my ILS video series I show you WHEN to press APP and the pit falls of pressing it too early.

 

The link to my YouTube Channel is in my signature.

[pvarn]

The ILS system has a maximum range of about 25-30 miles. The maximum range for glide slope capture is between 19-22 miles. Do not activate APP mode until you you see the GS needle lock to the top of the display. If you activate too soon, the GS will fail. Also, activating APP mode without the GS too far out sometimes results in the ILS needle being reversed. I always wait a few miles after I see the ILS frequency and needle activate to watch for a reversal. If the runway HAS a GS, I ALWAYS wait the GS needle. If you do not, you will get an ILS only approach.

 

Make sure you are not too high or too low for the GS capture. As a rule of thumb (if you lack charts) in airliners, this is about 4000 feet above ground level around 10-14 miles from the runway.

 

Learning these few fundamentals is something every new pilot has trouble with in FS.

 

-Pv-

[Yajvan]

Oh thanks to both of you above! that solved my problem. Made 2 ILS landings smoothly after I saw this. My range was 25 nm. Btw, what is that GS needle? e.e

 

(problem after problem.. sorry about that) I am getting FPS lag if i fly above 7000m. IDK why... one more question.. how can i make other planes appear in FSX? I have some add ons. I wann amake them appear rather than the default ones like orbit, pacifica, etc...

[mrzippy]

Oh thanks to both of you above! that solved my problem. Made 2 ILS landings smoothly after I saw this. My range was 25 nm. Btw, what is that GS needle? e.e

 

(problem after problem.. sorry about that) I am getting FPS lag if i fly above 7000m. IDK why... one more question.. how can i make other planes appear in FSX? I have some add ons. I wann amake them appear rather than the default ones like orbit, pacifica, etc...

 

Make sure your aircraft select page has all the boxes looking like this one.

 

[Yajvan]

no i mean ingame... as flights in the airport.

[mrzippy]

no i mean ingame... as flights in the airport.

 

OK, then the term is AI aircraft. So are you saying you have downloaded and installed some AI aircraft? Then you would need flight plans for each of them. Or use something like WOAI (freeware) or a payware AI program.

[lnuss]

Btw, what is that GS needle?

 

The GS (Glide Slope) needle indicates the vertical path you should fly to get to the runway, just as the localizer needle indicates the horizontal path. Together they make an ILS, Instrument Landing System. When flying manually, with each of those needles, you "fly towards the needle," that is, if the GS needle is above center then you're below the glide slope and need to reduce your rate of descent a little.

 

In the real world these two are short range radio systems, so FS imitates this, thus the short distance away from the airport where you can pick up the signal.

 

and the omnibearing selector.

 

When you are on an ILS frequency the OBS serves no operational purpose, though you can move it if you like -- it just doesn't affect the needles or the aircraft's flight path.

[pvarn]

Looks like some study of the FSX Learning Center and flying some tutorials (homework) is needed so you'll understand the basics with fewer questions needed.

 

-Pv-

[lefu]

A final approach (the green feather or glideslope) is about 10 kilometers (6 miles)

so i usually add that same distance (or 10 miles instead of 6 ) before catching loc, once i get to that distance i push the loc button.

[srgalahad]

"About" is another way of saying "close enough for government work"

In FS the localizer signal range is set at 27nm so beyond that there is no signal to be picked up.

The 'typical' (standard) glide path is 3 degrees (some, in the real world are 3.5-4 and odd ones are higher but are noted if so) which is 3 ft per 100. Working out the math, that is 1823 ft. above the runway threshold at 5 nm (a NM being 6076 ft) or 3650 ft at 10 nm.

For some reason (maybe confusion between NM and statute miles?) FS seems to have it set or described as 1500-1600 at 5 miles. (close enough)

 

The "10 mile' target distance came about from the desire for larger aircraft to fly a stabilized approach - ie. configured for the approach sufficiently far back for the major adjustments to be made well before GP capture (from below the GP). Since fuel efficiency became paramount the methods have changes slightly (gear up until GP acquisition to reduce drag - as the needle starts to move, gear down which also slows the aircraft naturally without requiring major power change while the pitch change to maintain the GP balances speed).

Of course, being too low too far out means you have to contend with another parameter - terrain clearance (for which there are real world standards that didn't really get implanted in FS precisely - close enough?)

 

All this is designed for both safety (trying to intercept the GP from above is difficult and hazardous due to high sink rates) and efficiency. STARS and vectoring practices also are designed to make the LOC intercept between 30 and 45 degrees to avoid abrupt turns, provide clear, easy-to-recognize instrument indications, but minimize 'long' approaches (if you have a 30* intercept heading set on the AP and then select APP when the LOC needle starts to deflect, you will probably see the aircraft turn a bit to make a 40 degree intercept - MS's design parameter).

 

While aviation may not be 'exact' it is based on science and measurement. Regrettably, FS was not built around a 'progressive learning' methodology where these bits would be covered in mandatory ground schools:rolleyes:

[il88pp]

a glideslope is 3 degrees. This is a 5% slope. Meaning 5 ft per 100.

 

5NM = 30.000 ft (1NM = 6000 ft)

So, how many feet down?

30.000ft = 300 x 100

and we know 5ft down per 100

5 x 300 = 1500 feet down.

 

for ten NM 10 x 300 = 3000 ft down.

 

:cool:il88pp

[StringBean]

Sorry, I am a bit of a stickler when it comes to math.

 

A 3° slope is more like 5 1/4 ft/100ft.

 

A 3% slope would be 3 in 100.

 

And there is no standard slope for a glideslope, they can vary quite a bit.

 

And glideslope interception altitude varies depending on the approach.

 

There is no "standard glideslope interception altitude". It will change from approach to approach.

 

peace,

the Bean

[pvarn]

Looks like the OP was satisfied after message #6.

 

-Pv-

[il88pp]

*******

Now you may ask, how do I make sure I fly a 5% slope? How to fly a 5% slope manually? (What Groundspeed and VS required).

What you need to know is:

What VS do I need, at my current Groundspeed, to fly a 5% slope???

 

"5% slope is 100 Units forward to 5 Units down."

That also goes for:

"5% slope is 100 Units of speed forward to 5 Units of speed down."

descent speed : 5 = forward speed : 100

descent speed = forward speed (in knots) : 100 x 5

But that would give a descent speed in knots. Yes it will. read on.

 

***********

First, how to convert those units:

knots and ft/min are both just speeds, given in different units.

1 knots=

1 NM/hour=

1 x 6000 ft/hour=

=6000ft/hour=

6000 : 60 ft/min=

100 ft/min

So, 1knot = 100 ft/min

 

********

We continue from:

Descent speed (knots) = "forward speed (knots)" : 100 x 5

To get a speed in feet per minute we use the (1knot=100ft/min) we found earlier.

"descent speed (ft/min !!)" = ["forward speed (in knots)" : 100 x 5] x 100

The 100 devides away nicely, (100 : 100 =1) , leaving:

For a 5% descent, "descent speed" (in ft/min !) = forward speed (in knots !) x 5"

 

If you want to fly a 4% slope, same thing leads to: "descent speed (ft/min)" = 4 x "forward speed (knots)"

You can use this in any part of your descent from cruise altitude. (and also for climbs of course.)

Remember to use Groundspeed.

 

Enjoy,

il88pp:)

 

p.s.

I did round down 1NM to 6000 ft. It's actually a few feet more.

To be perfectly accurate, 1knot is 101.268591 feet / minute

but using that value does not have any significant effect on the calculated VS.

So my approximation is fine to use.

[mrzippy]

Looks like the OP was satisfied after message #6.

 

-Pv-

 

But the wheels of the bus go 'round and 'round! That's where he changed over to wanting AI at his airport.