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Thread: FSX Learjet 45 GPS Autopilot Issue

  1. Default FSX Learjet 45 GPS Autopilot Issue

    Hi,

    Just started playing FSX - getting back into flight simulation for the first time since I was a kid. I thought I'd got my head around the Learjet controls for the autopilot and the GPS as I've managed a few succesful IFR flights and a couple of successful ILS landings. However, I just took off on another flight and I can't get the Learjet to follow the GPS anymore, it keeps vearing off to the right - as you can see, much to the annoyance of ATC.

    This is the first time I've taken off straight away again after an ILS landing and refuel (as opposed to going back to main menu and setting up a new flight) so wondering if I've failed to reset something correctly?

    Click image for larger version. 

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    Any hints gatefully received!

    Mark

  2. #2
    Join Date
    Jan 2012
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    Default

    If you want to follow the GPS, then be sure to turn the NAV/GPS switch to GPS or just make sure the NAV light is off on the GPS. Also you can file a GPS flight plan. When Flying IFR and using ATC for directions, they will have you make some turns every which way but loose to keep you on course.

    Be sure to make your responses to ATC in a timely manner or they will drop you like a hot potato.
    Mr Zippy Sent from my keyboard using "Whackamole", NudgeAKey + 2 Fingers

    Emachines T3418 AMD 3400+ processor 2GHZ/256KB L2 Cashe 2Gig Ram 160Gig HDD NVidia GEForce 6100 GPU Running WinXP Home Can't believe it still works! Running FSX Standard with SP1 and SP2

  3. Default

    Hi,

    As shown in the screenshot above, the GPS/NAV switch is set to GPS, but it is still dragging me off course to the right.

    I believe I had filed the plan correctly and ATC seemed to be working fine - I was just occasionally a bit late acknowledging them while debugging my autopilot.

    Mark

  4. Default

    Quote Originally Posted by fbjimmy View Post
    This is the first time I've taken off straight away again after an ILS landing and refuel (as opposed to going back to main menu and setting up a new flight) so wondering if I've failed to reset something correctly?
    I've seen this before myself, when you've used autopilot in VOR/NAV mode (as you would on an ILS) and then you try to go back to GPS/NAV the plane won't track the magenta line properly. I don't think it's you, I think it's a bug in the sim and I think it's been there since FS9 and maybe earlier. Probably what it's trying to do is track an imaginary line to the right of the actual magenta line a few miles and ATC is throwing a hissy as a result.

    I hypothesize that AI aircraft track an offset course - so when you're flying KSEA to KLAX at FL320 and an AI is flying KLAX to KSEA at FL320 you don't crash into one another head-on. My hypothesis is that the sim confuses you with an AI once you've used VOR/NAV on the autopilot and tries to put you on an offset track. Just a guess, maybe I'm completely off base.

    You might try reloading the airplane prior to taking off on the next leg, that seems to work for me but of course I never remember to do that until I'm 10,000' in the air!

  5. #5

    Default

    That's it. Reload your airplane. Or, better yet, load the C-172, look at panel switches, press 'D' and 'B' key and then load your airplane and everything should reset to 'default'. I think you are 100% correct Jim in your assesment of this aspect, or bug. Makes a lot of sense. Who knew! We learn something everyday, don't we. Cheers.
    Chuck B
    Napamule
    i7 2600K @ 3.4 Ghz (Turbo-Boost to 3.877 Ghz), Asus P8H67 Pro, Super Talent 8 Gb DDR3/1333 Dual Channel, XFX Radeon R7-360B 2Gb DDR5, Corsair 650 W PSU, Dell 23 in (2048x1152), Windows7 Pro 64 bit, MS Sidewinder Precision 2 Joy, Logitech K-360 wireless KB & Mouse, Targus PAUK10U USB Keypad for Throttle (F1 to F4)/Spoiler/Tailhook/Wing Fold/Pitch Trim/Parking Brake/Snap to 2D Panel/View Change. Installed on 250 Gb (D. FS9 and FSX Acceleration (locked at 30 FPS).

  6. Default

    Hi Chuck, good to hear from you! Afraid I was wrong though, lol.

    Nothing a guy hates worse than de-bunking his own theory but here goes: I made up a quickie AI traffic .bgl that flies the CRJ700 back & forth between KSFO and KSEA every 8 hrs, then I loaded up at KSFO and followed him. I passed him somewhere near Mt Shasta and he certainly wasn't flying an offset route! I think I rubbed his belly on the way by with my vertical stab, lol.

    Click image for larger version. 

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    BTW, how does he "have the traffic"? Does he have a back-up camera on the tail of that RJ or what?

    No idea why using VOR/NAV makes GPS/NAV fly an offset track. I tested it out in P3D v3 as well on the same flight where I tracked RBL VOR on VOR/NAV for a bit then when I went back to GPS/NAV the plane tracked to the left of the magenta line and seemed to settle in at about .64 nm off track. Then I reloaded the airplane (which wasn't exactly a serene experience at FL270 & 330 kts) and it swung right back onto the magenta line.

  7. #7

    Default

    Explaining this mystery is going to take time. Give me a year and MAYBE I can come up with something. Right now I am thinking 'wind?'.' Hot Air?' (sorry, had to say it - hehe). Maybe you just need new GPS hardware? Either way it is not going to keep me awake at night. This is too 'deep' for my brain so I am just going to let it go. How's that? I am OLD enough to know when to quit (ha). Cheers.
    Chuck B
    Napamule
    i7 2600K @ 3.4 Ghz (Turbo-Boost to 3.877 Ghz), Asus P8H67 Pro, Super Talent 8 Gb DDR3/1333 Dual Channel, XFX Radeon R7-360B 2Gb DDR5, Corsair 650 W PSU, Dell 23 in (2048x1152), Windows7 Pro 64 bit, MS Sidewinder Precision 2 Joy, Logitech K-360 wireless KB & Mouse, Targus PAUK10U USB Keypad for Throttle (F1 to F4)/Spoiler/Tailhook/Wing Fold/Pitch Trim/Parking Brake/Snap to 2D Panel/View Change. Installed on 250 Gb (D. FS9 and FSX Acceleration (locked at 30 FPS).

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