SurClaro Flight Simulator Resources

Posted: Mon Jul 02, 2007 10:09 am Post subject: ILS Flight Question

Hi .. When i fly ILS flights .. i usually have my gps route on aswell .. and i see that the ATC instructions lead me off that route ? what do i do ? because then they tell me to correct course when i change the route .

Posted: Mon Jul 02, 2007 10:50 am Post subject: most likely..

The most common cause for this, that I know of, is you have made a "direct to" route on your gps, but of course nobody gets to fly in a straight line from airfield to airfield so you would have to use the normal jet-routes and waypoints method to be more closely aligned with what ATC will tell you.

Posted: Mon Jul 02, 2007 11:12 am Post subject:

Well my flightplan uses the IFR ... one time the atc took me away from the airport !!!

Posted: Mon Jul 02, 2007 2:07 pm Post subject:

May be for the final ILS approach?

If during your flight setup you have "Direct - GPS" selected then you are not flying ILS, you are flying IFR, unless you select VFR. ILS: Instrument Landing System, only used during landing.
So, I think what you are asking is why you get the deviation when following ATC when nearing the airport using a Direct - GPS flight plan? Wink

The reason for that is:
The GPS plots a straight line (well, great circle) course to the center of the airport you are flying to. Not to any specific runway, NAV beacon, or VOR. You need to tell the GPS where you want to go.
In the Direct - GPS Mode you do get to fly in a straight line (even in real life) to get near the airport, then ATC "blends" you into the traffic pattern for landing, because the Sim in its current state does not allow for GPS landings. These are called RNAV (GPS) IAPs (Instrument Approach Procedures). GPS is not supposed to be used for precision approaches because the altitude reporting factor of the GPS is not a good enough reference to do them, the GPS is really good at fixing your latitude and longitude coordinates on the face of the Earth. But since it is satellite based, it's not so good at figuring out how close you are to a Low Earth Orbit satellite in elevation.
This is why ATC tells you to "Expect vectors, ILS runway XX..."
Now the sad part of this is that you still have to tune your NAV Radio to the Localizer freq for that runway or your ILS won't lock up on the localizer and the "APP" button for the Auto Pilot will not work properly.
But there is a saving grace, you can quickly program your approach into the GPS and it will fly most of it for you, you will still have to land manually. GPS does not rely on a radio, so it can't make you climb or descend, this is why you have to be hands on stick and throttle for this type of landing.
And since there are two GPS units available, although similar but different in layout, I will not offer any info on that here.

The real short answer is to follow ATC and program the GPS to make the approach. Cool

Posted: Tue Jul 03, 2007 1:51 am Post subject:

Ah.. but i dont use direct GPS... maybe this helps you guys out to figure wats goin on .. When i start up i get tower clearance .. then i taxi IFR .. Then i request takeoff IFR.. When i take off i am given this order .. Runway heading Climb and Maintain *******. Then after about 2 thousand ft i get turn left/right ***. i get that for a while but i find that the IFR course on my GPS is not even cloose with my IFR that the ATC is giving me !!

Posted: Tue Jul 03, 2007 2:21 am Post subject: Um... What?

Your IFR course is not going to be the same as your GPS, the sim is going to route you into a outbound traffic pattern, remember I said that until you get close to the airport then ATC will "blend" you into the traffic, it's the same with departures. You have to follow the out bound traffic, and there is no way around this. You need to follow the ATC and do what they ask until you hear, "turn X and resume own navigation" this will allow you to turn on NAV mode and the aircraft will turn to track the GPS path via the auto pilot.

Does your flight planner look similar to the attached?

Posted: Wed Jul 04, 2007 5:02 am Post subject:

um well ive got FS2002 yeh it has the same features i guess. Ok so when they say maintain own navagation its ok to switch to Nav Autopilot ?

Posted: Fri Jul 06, 2007 3:34 pm Post subject:

Absolutely Smile