SurClaro Flight Simulator Resources

Posted: Wed Feb 16, 2005 2:29 pm Post subject: APPROACH HOLD SWITCH (Need Help)

I've been flying ILS for ages but I never really figured out what the APPR hold switch does.

Thanks

Posted: Wed Feb 16, 2005 6:31 pm Post subject:

Skylar, you probbably mean you have been flying IFR for years...because ILS is short for Instrument Landing System, and there is not much flight after that Wink

The APP button is a part of the Autopilot System, to understand better I will explain a situation and the flow of events after catching the localizer beam.

1. The right ILS nav frequency is tuned it either NAV1 or NAV2 radio, and the correct ILS heading is tuned on the CRS (Course) box. By doind that you are finishing the first step of a fill procedure ILS apporach

2. At about this time you are already levelled off at 3000 AGL (example, most of the cases that is the initial altitude for entering an ILS approach). Then approach the localizer beam from one of the sides with not more then 45 degrees off. And do it so that you are established on the localizer at least 15 miles DME from the treshold. That will give enough time to easily establish and maintain the course...with careful attention to the wind. NAV button on the AP panel will do the job for you if you have a hard time coping with the wind. Now....after the vertical needle starts to move, that will indicate that you are slowly intercepting the glideslope, and soon you will have to start decending. That is when you turn the APP button on and it will follow the glideslope and the localizer and put the airplane down on the ground. You still have to operate throttle, flaps, geat and spoilers. After setting the plane on the ground the AP comes off and you screech the plane all the way to the gate.

Again I have written a whole article when I could have answered it with a single line Shocked

Posted: Wed Feb 16, 2005 6:37 pm Post subject:

well from what I can say....and I never do ILS approaches...the appr switch will hold your plane lined up with the gps assigned runway.
However you can control the VS until touchdown. I however switch it off about 3mls before the threshold..otherwise the aircraft will turn into the assigned holding pattern for that runway after you crossed the runway boundary...thats what I can say as an casual flyer with a big lack of navigational knowledge Embarassed

Posted: Wed Feb 16, 2005 6:41 pm Post subject:

well max...percise as always. Smile

thats the way ....i kinda said it with a few words less ..but also less basic knowledgement of aviation terms

Posted: Wed Feb 16, 2005 8:41 pm Post subject:

All right great!! Thanks for the tip! Is the course the same as the heading?

Posted: Fri Feb 18, 2005 3:19 am Post subject:

I would imagine that you are talking about the course setting on the AP. If you are, then, no, it is not the same as the heading. The Course has to do with VORs and what not. You basically select the radial you want to fly towards or away from the VOR.

VOR's have 360 radials, or one for every degree of the compass. They are numbered for the oubound direction, so thus, the radial that points north is 360, the one that points south is 180, etc. You adjust the course to reflect which radial you wish to fly on. For example, if you were heading east towards the VOR and wanted to head in on the 270 radial, but were on the 280 radial (slightly north of the radial you wished to be on,) you could spin the course setting to 90, and then turn south. When the needle centers, than you would turn back east. You would now be on the 270 radial.

The example is shown on this really bad drawing I made. Your plane is the blue thingy, the VOR is the red thingy, and the green line is the path that my example shows.

http://img.photobucket.com/albums/v475/InsuredDisaster/VOR.jpg

Posted: Fri Feb 18, 2005 8:44 am Post subject:

gotta love that drawing.. Wink

Posted: Fri Feb 18, 2005 9:14 am Post subject:

LOL...but an easy to understand answer...ID...well done.

Wink

Exxman

Posted: Fri Feb 18, 2005 1:29 pm Post subject:

yes, it was explain very well.
Now can you explain about the "BC" button on the AP?

Please.

Posted: Fri Feb 18, 2005 2:07 pm Post subject:

I will attempt to explain it...if not Ben will draw it later.... Wink

The BC means the Back Course hold and it is for runways that have ILS on only one of the sides....example rwy 34 has ILS but 16 doesn't. Well if you would just enter the 160 to be the course it wouldn't enough....not for the AP because then the needle would be mirored...and that would make bannanas with autopilot. So you are too left and the neddle shows you are to right, the ap goes left because the AP only sees where the needle goes. So it would be an endless attempt to go right by turning left. The BC only fixes that problem...so that when approaching fromt he other direction you can use the ILS at least for lateral navigation.

I hope it has been clear enough.

Posted: Fri Feb 18, 2005 3:35 pm Post subject:

Bananas?

Here's a Localizer Backcourse description that might help you. Get the full lesson here: http://www.navfltsm.addr.com/index.htm

The Localizer Back Course

"...the localizer antenna array is located at the far end of the runway, away from the approaching aircraft. Its antennas are arranged and manufactured in such a way to transmit a narrow signal on the runway approach path. That localizer signal is so accurate that with its guidance, along with the glide slope signal, an aircraft can safely land when the visibility is zero and when the ceiling is zero.

However, the Localizer antenna array also radiates a narrow signal beam in the opposite direction of the approach path. That signal is called the Localizer Back Course."

Posted: Fri Feb 18, 2005 4:21 pm Post subject:

I should have been more clear, the aircraft goes bananas witht he AP and NAV turned on when flying a Back Course approach.

And Rick, pardon me for asking, but wasn't that what I said. I am asking not to engage in a combat, but because I con't make a difference whether you are correcting me with that article or are you making my post more undersandable. Either way, I thank you. Very Happy

Posted: Fri Feb 18, 2005 4:50 pm Post subject:

I was simply trying to make the subject more understandable and to also provide the guy with a link so that he could look up more information on that subject.

Rick

Posted: Mon Feb 21, 2005 12:49 am Post subject:

I have recently tried to land the 737 with ILS landing and i don't know what happened but every time i tried, the plane always oversteered and missed the runway. The altitude was also a little too low. I was like half a mile behind the runway and the plane was touching down. Please Help!

Posted: Mon Feb 21, 2005 3:24 am Post subject: