Jump to content

Archived

This topic is now archived and is closed to further replies.

Guest Peter W

747 Keeps missing the runway!!

Recommended Posts

Guest Peter W

I'm flying the 747-400 in FS9. Just recently all my flights now miss the runway. I've attached some screenshots of a typical approach to London Heathrow, approaching from Biggin Hill, with a planned landing on 27R. Every thing is fine until I'm in the final approach and try and capture the ILS. I click the LOC then APP buttons, LOC goes out and the 3 autopilot lights come on. However the VNAV light stays on. The 747 is on the glide slope OK, but not aligned with the runway. The NAV/RAD gives the correct ILS frequency of 110.1 and the pink blobs on the dispalys tell me where the ILS beam is relative to the 747, but the aircraft does not appear to want to track it!Any ideas?Regards,Peter W

Share this post


Link to post
Share on other sites

It is real hard to make out details in these pics, but it looks like to me that you are turning onto the final course before you get to the localizer; hence, never intercepting the LOC you don't shift into AUTOLAND...and stay in LNAV/VNAV.Is it possible you added a scenery or AFCAD file lately? It also looks like your ND has the final course and runways in the wrong place... use slew to put her down on the numbers. The LOC should be centered (your pink blobs, I like that.. they are called course deviation indicators or glide slope indicator) but I bet the ND displays the runway in the wrong spot.. weird. I think something is messing with your FS9 scenery, but I haven't seen this exact symptom before. For some reason the lat/lon of the runway is "shifted." Mag deviation file corruption can cause something like this but different.While on the ground in slew mode, check the FS lat lon and compare it to the actual runway, and that should be the same as in the navdata wpNavAPT.txt file.


Dan Downs KCRP

Share this post


Link to post
Share on other sites
Guest Jake Lee

Try using ALT HOLD and HDG SEL instead of using LNAV/VNAV. Do you have the correct runway and final approach procedure selected and activated in the FMC? Maybe it's pilot error.- Jake

Share this post


Link to post
Share on other sites
Guest Peter W

Hi Dan,Thanks for your help. I've checked out the location of the end of runway 27R and an aircraft on the end of the runway has exactly the same long / lat as the data in the WPNAVAPT.txt file, so thats not the problem.I then created a circular route that both took off and landed on 27R. Before take off the FMC location agreed with the location in the WPNAVAPT file. Everything went fine until the final approach, when the same problem occured. LOC was clicked, then APP, the 3 autopilot lights came on, but the VNAV stayed on. Upon inspection of the FD screen the LOC and G/S indicators are in white, which suggests that the localiser and glide slope are armed but not captured. My angle of approach is not that far off the proper line, so its not as if I'm a million miles away from the runway and at a crazy angle!So the question is how do I get it to capture the localiser?Any more ideas, should I re-load the 747 sofware?Regards,Peter W

Share this post


Link to post
Share on other sites

My guess is the reason you don't intercept the LOC is because the instructions to turn to final course in the sidstar file have you turning before you actually get to the LOC... and in this case the fix is to change to HDG while on that intercept course until capture.The reason the localizer isn't where it should be, again my guess, is probably due to a add-on scenery or afcad file you may have recently installed. You can use the scenery library manager to turn off the add-ons (they are not deleted) to see if the localizer then behaves correctly (I expect it will) then use elimination to narrow it down to the offending scenery. I see this problem in this forum about once every 4-6 weeks... has something to do with corruption of magnetic declination somehow.This problem will probably not be solved by reinstallation of the pmdg.Hope this helps.


Dan Downs KCRP

Share this post


Link to post
Share on other sites
Guest Peter W

Hi Dan,Thanks for all your suggestions and help. It turns out that the problem was due to the fact that the WPnavAPT file assumes that the orienation of Heathrow runway 27R is 275, but the ILS beam in FS9 is aligned on 273. The STAR that gave me the waypoint (IRR7.5) 7.5 miles from the threshold is co-locacted 7.5 miles on the 275 orientation, so although I was over the waypoint, I was not aligned with the ILS beam. Once I flew the 747 further north, the LOC and G/S became captured. - Problem solved!! Perfect Autoland!I just wonder how many other airfields have the runway and ILS beam not quite on the same alignment!Regards,Peter W

Share this post


Link to post
Share on other sites
Guest Jake Lee

Doesn't Boeing recommend you use HDG SEL instead of LNAV to capture the localiser?- Jake

Share this post


Link to post
Share on other sites

Good find. The MSFS scenery seems like it is based on FS2002 in many areas, a few FS2004 updates but the FSX scenery didn't seem to update data (just eyecandy)... whether true or not, their navdata is obsolete including magnetic deviation. Every time I open a stock afcad I can find misplaced approach DMEs, localizer courses slightly skewed, even runways not exacly where they should be.Now that you mention your finding, I remember simming into EGGL and having to maintain HDG instead of LNAV to intercept the localizer. Forgot about that... I had mentioned it to Stephen Bell (I was using his procedures, highly recommended) but I didn't understand the source of the error. I wonder if the megascenery Heathrow got it right? I used to have this until the computer failure, it's on my long replacement list.


Dan Downs KCRP

Share this post


Link to post
Share on other sites

  • Tom Allensworth,
    Founder of AVSIM Online


  • Flight Simulation's Premier Resource!

    AVSIM is a free service to the flight simulation community. AVSIM is staffed completely by volunteers and all funds donated to AVSIM go directly back to supporting the community. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. Thank you for your support!

    Click here for more information and to see all donations year to date.
  • Donation Goals

    AVSIM's 2020 Fundraising Goal

    Donate to our annual general fundraising goal. This donation keeps our doors open and providing you service 24 x 7 x 365. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. We reset this goal every new year for the following year's goal.


    2%
    $705.00 of $25,000.00 Donate Now
×
×
  • Create New...