ILS confusion

[thaisteve]

Hi all, I'm new round here so go easy on me! Last night I flew an IFR route from London Heathrow to Glasgow using GPS waypoint navigation. I requested ILS runway 5 as my approach and set the correct approach/transitions on the GPS well ahead of time. All went perfectly until the last moment (after the GPS transitions had brought me perfectly in line with the runway) when it was time for me to switch from GPS to NAV mode. I had already input the ILS 5 frequency (110.10 if I remember correctly), and it was active on my NAV1. When I switched the Autopilot over to 'NAV' and selected 'APP', with the correct frequency, my airplane tried to steer 90 degrees or so to the right (clearly not where I was supposed to go) and put me into a steep descent- not good at 3000 feet. The HSI showed the same incorrect heading. I checked the ILS frequency which was correct, and I'm pretty sure that the Autopilot was set up correctly so am confused as to why this happened.
The only thing I can think of is this: I input the ILS frequency very early in the flight and switched on the Morse code signal for it early as well. To my surprise it picked up a morse signal about 300 miles away. Has my NAV1 'locked' onto something else, ie, not the ILS frequency I was wanting? Can this happen?  

[BFMF]

I would suggest practicing instrument flying, and instrument approaches in a much smaller and forgiving aircraft...

[Splinter562]

I could be a problem with FSX's data set. The navigation data was locked in sometime before the game was released, which means the 2005 to 2006 time frame. If you were flying off of a current chart, it is possible that the ILS frequency has changed and no longer matches FSX or that it's just wrong in FSX to start with. Clicking on the airport in the map view will tell you what FSX has listed as the ILS frequency.

[thaisteve]

I was flying the Lerajet 45 which I use most of the time. I have not encountered this before. I also did check the ILS frequency on the map as well as the GPS and they both displayed the 110.10. I guess this could still be incorrect.

[Anxyous]

Was your HSI set to the runway heading? If not, it might have attempted to head for another inbound course.

And maybe you forgot to disengage other parts of the autopilot?

I've had problems with the Learjet 45 autopilot as well...

[thaisteve]

Good question. I suspect this may have something to do with the problem. I did not have the HSI set to the runway heading, and in fact hadn't input any CRS data as was flying on autopilot purely with the GPS. This admittedly took me into a perfect straight approach with the runway, it was then that I switched from GPS to NAV mode with NAV1  tuned to the required ILS frequency and turned on APP. All other Autopilot hold/mode settings were disengaged. I wasn't aware that I had to also input the runway heading into the CRS selector as I presumed the APP/NAV1/ILSfrequency would be all I needed. Then again I'm new to all this and still finding my feet. I do however like to throw myself in at the deep end- wouldn't be doing that if it was a real aircraft of course!

[carter43]

Steven Thai?

[Wingo]

You don't have to adjust the CRS/OBS knob when on an ILS as it automatically aligns with the LLZ. While it is good practice to align the heading bug with the runway, it wouldn't have produced this error unless you accidentally activated the heading mode on the autopilot.

What setting did you have your CDI on? If you had left it on GPS instead of switching it to Nav 1 it may have caused this

[thaisteve]

I definately switched my CDI to NAV1, as that's when it became immediately apparent the aircraft wasn't doing what it should when it turned sharply to the right and started a descent. Funnily, the HSI needle was pointing at right angles to my direction of travel (in line with the movement of the aircraft) whilst the aircraft was heading straight to the runway. The aircraft was basically doing what the gauges said it should be doing, it's just that the gauges didn't seem to be picking up the ILS and therefore not doing what I wanted.
Sounds like a bug.

[Wingo]

How much deflection did you have on the LLZ CDI? It could be possible you were out of limits, but I doubt FSX would simulate it :?

[thaisteve]

By that I take it you mean the course indicator on my HSI/CDI? If so, then approximately 90 degrees clockwise from where it should have pointing. If you mean the horizontal deflection left or right, then the answer is none. The indicator showed a solid line, it did not display any horzontal deflection. Does that help answer your question- still getting to grips with all the anacronyms!

As I am still experimenting with it all it is difficult for me to communicate where I may have gone wrong, and no doubt I'm doing lots of things incorrectly though most of the time I do seem to be able to bring it all together. I've got a nagging suspicion that it may be something to do with this: As I was flying from Heathrow to Glasgow, and as I was using the Autoplilot/GPS navigation, the only NAV1 frequency I needed to input during the whole flight was the ILS frequency for landing. I decided to input this into the receiver shortly after taking off from Heathrow, thinking it good to get everything organised early on. I also turned on the NAV 1 identifier button thinking that, well, I'm not going to pick it up & hear the morse identifier until I get pretty close to Glasgow. In fact, the morse signal started coming through somewhere south of Manchester and it was at this point that I thought something may be wrong. Also the fact that when I did eventually switch to the approach mode and change from GPS to NAV1, the plane wanted to head south and descend. I don't know if it can happen, but to me it seems as though the receiver had picked up somewhere else, much earlier, south of my position and was trying to take me back there. That may shine some light on it for all you veterans.
Thanks for all your help by the way, really is appreciated.