Page 3 of 4 FirstFirst 1234 LastLast
Results 21 to 30 of 39

Thread: Uncommanded Dive

  1. #21
    Join Date
    Dec 2005
    Location
    Cwmbran, Torfaen, UK
    Posts
    721

    Default

    textrich and downwind. The rate of climb IS set as a +ve. I set it at 1,200 fpm but I have tried it as high as 2,000.

    I would point out that I'd flown A320's and B737's - 200 and 800's for a number of years. As well as B747's 200 and 400's, B727's, DC10, MD11, and never had problems. Then I uninstalled FSX about 4 years ago and only reinstalled this year, and this is when the problems started.

    And I would remind you what I said in an earlier message, that the same thing happens with the default B747 and with an added Camsim A350.



    Rick, I don't know how to add pics but I understand what you're saying and I'll look into it later and forward pics.


    Thanks for your inputs. Will get back with pics later.

    Allan

  2. #22
    Join Date
    Jun 2017
    Location
    South Florida
    Posts
    3,588

    Default

    Allan - Just as a quick reference to check yours, here is the [autopilot] section of my B737-800 aircraft.cfg. Just compare it to yours to see if there is any significant differences between the two!
    Looks like you and anyone trying to help you solve this, will be "shooting in the dark" as, I for one am at a loss as to what is going on? What really is confusing, you say you got a successful flight from your A321, okay, why not with the B737 then? This is why I suggested just focusing in on the B737 for now.
    Good luck Allan!

    [autopilot]
    autopilot_available=1
    flight_director_available=1

    default_vertical_speed=800 <<<<<< Yours might be significantly be higher, I toned down this entry, so I wouldn't get a big drop in ILS engagement! I think default might be 1800??

    autothrottle_available=1
    autothrottle_arming_required=1
    autothrottle_max_rpm = 90
    autothrottle_takeoff_ga=1
    pitch_takeoff_ga = 8;
    max_pitch=10.0
    max_pitch_acceleration=1.0
    max_pitch_velocity_lo_alt=2.0
    max_pitch_velocity_hi_alt=1.5
    max_pitch_velocity_lo_alt_breakpoint=20000.0
    max_pitch_velocity_hi_alt_breakpoint=28000.0
    max_bank=25
    max_bank_acceleration=1.8
    max_bank_velocity=3.00
    max_throttle_rate=0.10
    nav_proportional_control=9.00
    nav_integrator_control=0.25
    nav_derivative_control=0.00
    nav_integrator_boundary=2.50
    nav_derivative_boundary=0.00
    gs_proportional_control=9.52
    gs_integrator_control=0.26
    gs_derivative_control=0.00
    gs_integrator_boundary=0.70
    gs_derivative_boundary=0.00
    yaw_damper_gain = 1.0
    Last edited by Downwind66; 12-01-2020 at 08:45 AM.

  3. #23
    Join Date
    Dec 2005
    Location
    Cwmbran, Torfaen, UK
    Posts
    721

    Default

    Hi Downwind,

    This is my Autopilot. The differences are highlighted.

    The difference in the figure mean nothing to me.

    [autopilot]
    autopilot_available=1
    flight_director_available=1
    default_vertical_speed=1800
    autothrottle_available=1
    autothrottle_arming_required=1
    autothrottle_max_rpm = 90
    autothrottle_takeoff_ga=1
    pitch_takeoff_ga = 8;
    max_pitch=10.0
    max_pitch_acceleration=1.0
    max_pitch_velocity_lo_alt=2.0
    max_pitch_velocity_hi_alt=1.5
    max_pitch_velocity_lo_alt_breakpoint=20000.0
    max_pitch_velocity_hi_alt_breakpoint=28000.0
    max_bank=30,25,20,15,10
    max_bank_acceleration=1.8
    max_bank_velocity=3.00
    max_throttle_rate=0.10
    nav_proportional_control=12.00
    nav_integrator_control=0.25
    nav_derivative_control=0.00
    nav_integrator_boundary=2.50
    nav_derivative_boundary=0.00
    gs_proportional_control=25.0
    gs_integrator_control=0.53
    gs_derivative_control=0.00
    gs_integrator_boundary=0.70
    gs_derivative_boundary=0.00
    yaw_damper_gain = 1.0


    Screen shots to follow (I hope)

  4. #24
    Join Date
    Dec 2005
    Location
    Cwmbran, Torfaen, UK
    Posts
    721

    Default

    Click image for larger version. 

Name:	1. Ready For Takeoff 2.jpg 
Views:	14 
Size:	204.8 KB 
ID:	224042

    Ready For Takeoff


    Click image for larger version. 

Name:	2. Just airborne - Not cleaned up - About 280 ft 2.jpg 
Views:	15 
Size:	139.6 KB 
ID:	224043

    Just Airborne


    Click image for larger version. 

Name:	3. Autopilot engaged - Aircraft Cleaned Up - Note the high nose up 2.jpg 
Views:	22 
Size:	191.7 KB 
ID:	224044

    A/P and A/T engaged. Note the high nose up.


    From there the aircraft pitched up sharply any quickly, stalled and fell from the sky.

  5. #25

    Default

    Your trim setting is likely out of whack. The autopilot can only retrim so fast when engaged. If your trim is too hi NU, the AP cannot retrim fast enough to prevent this pitchup at engagement.

    Try a manual takeoff and initial climb without autopilot - that will tell you if your trim is out of line with your weight / cg location. If you have to fight to keep a typical transition attitude / acceleration to 250 KIAS (need to trim a lot nose down), that is the problem.

  6. #26
    Join Date
    Dec 2005
    Location
    Cwmbran, Torfaen, UK
    Posts
    721

    Default

    Trim setting is 0.0 deg.

    And why should this be a problem now when I flew for a number of years previously without even considering my trim?

    And the trim is the same with the B737 and the A321, with similar payloads, fuel, etc, and I can takeoff with the A321.

  7. #27
    Join Date
    Jan 2012
    Location
    San Francisco, California
    Posts
    18,159

    Default

    My question is why is your N1 button on the autopilot on??? With that lit, you are not setting the auto-throttle to the 240 kph but to follow your N1 input, which is set to 0%.

    Your airspeed in your last shot is at 124 knots....bad...bad! By that time you should be close to 230 knots and speeding up!

    Name:  Screenshot 2020-12-01 at 8.49.50 AM (1).png
Views: 42
Size:  128.1 KB
    Last edited by mrzippy; 12-01-2020 at 12:51 PM.
    Mr Zippy Sent from my keyboard using "Whackamole", NudgeAKey + 2 Fingers

    No flight Sim installed until I get a new computer.

  8. #28
    Join Date
    Apr 2017
    Location
    Massachusetts
    Posts
    93

    Default

    On top of the other posters' recent comments on your photos, I believe your SPEED button needs to be activated and the A/T ARM needs to be ON. In the diving photo A/T is on but SPEED is not on. I fly with a Saitek Flight Panel so I don't always pay attention to the aircraft's autopilot panel itself. However I am reasonably for the default 737 both need to be engaged so you do not eventually lose speed with the nose up.

  9. #29
    Join Date
    Dec 2005
    Location
    Cwmbran, Torfaen, UK
    Posts
    721

    Default

    Oops.

    Just selected speed instead of N1 and smooth takeoff. Can't understand what happened there, I NEVER, EVER, run with N1 set. So not convinced this it the total solution but certainly worked this time. Time for dinner. Will try a few more takeoffs later.

    Thank you all for your input. Watch this space.


    Allan

  10. #30
    Join Date
    Jun 2017
    Location
    South Florida
    Posts
    3,588

    Default

    [QUOTE=mrzippy;2138198]My question is why is your N1 button on the autopilot on??? With that lit, you are not setting the auto-throttle to the 240 kph but to follow your N1 input, which is set to 0%.

    Your airspeed in your last shot is at 124 knots....bad...bad! By that time you should be close to 230 knots and speeding up!

    Yep, Charlie, N1 set at zero, Speed button not engaged, 124 KIAS in a Boeing 737 would definitely cause a stall. Poor Boeing never had a chance!

    If Allan did accidentally hit the N1, he could have very well done it at other times, something he needs to pay attention on not doing!

    Allan, here is my panel during climbout on a default B737-800. I find 1800'/min vertical speed very comfortable in a climbout to higher altitudes, but settings can change with obstacles etc.

    Click image for larger version. 

Name:	2020-12-1_14-20-24-117.jpg 
Views:	6 
Size:	269.0 KB 
ID:	224046

    And, a external view of the aircraft for the above panel settings. Aircraft looks very content!
    Click image for larger version. 

Name:	2020-12-1_14-20-29-824.jpg 
Views:	4 
Size:	243.6 KB 
ID:	224047

    And you know what Allan, things are starting to make sense of how it is happening. You had successful flights in the A321 and not in the Boeing 737, why is that? Well, could be that the A321 has no N1 preset! You could have very well have been accidentally hitting that N1 button all along? Make several flights with the Boeing and see if your issues have gone away. We all hope that they have!

    Rick
    Last edited by Downwind66; 12-01-2020 at 03:58 PM.

Page 3 of 4 FirstFirst 1234 LastLast

Similar Threads

  1. Dive!!! Dive!!!
    By joe23 in forum MSFS Screen Shot Forum
    Replies: 8
    Last Post: 09-23-2010, 02:23 AM
  2. Uncommanded failures
    By The Sled in forum FS2004
    Replies: 2
    Last Post: 01-24-2006, 10:47 PM
  3. Uncommanded View Change
    By martinconnor in forum FS2002
    Replies: 7
    Last Post: 01-11-2003, 11:25 AM
  4. Replies: 4
    Last Post: 05-30-2002, 02:37 AM
  5. Replies: 1
    Last Post: 02-10-2002, 04:36 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •