How to get a clean autopilot?

1st Official Post

    Hi

    As title says: how can I get a clean autopilot in B737. I do not understand the logics. I still have a lot of issues with the B737 autopilot, with and without a flight plan. I would like to have a 'clean' autopilot, i.e. nothing is configured, no speed, no altitude nada. I dislike when things are preconfigured I do not know. When I configure the plane on a rwy ( necessary as some think possibility to configure plane in air in pause mode is not realistic). Hence I configure plane on rwy and move it then to approach distance to the rwy in a reasonable altitude. But when starting at that position all my configuration got lost: speed is 293 and not 220 as I wanted, VS is 6000. This is really anoying. Also the autopilot disengages during a flight plan flight in the middle of climbing after a minute or so. I cannot reengage it anymore as the plane goes into a steep climb. The 737 behaves like a wild horse an I cannot ride it. I will use the sim for VFR flights with small airplanes, that's what it was made for and not touch the B737 anymore as this is frustrating. Maybe others like the Dash and Airbus are ok but I am not familiar with those.

    I read almost nothing about the B737 here. I nobody else flying it?

    Regards,

    Thomas

    Regards,

    Thomas

    i7-14700KF @ 5.6 GHz, Geforce RTX 4090, 32MB RAM, 1TB SSD M.2, 1TB SSD M.2, 2TB SSD M.2, 32" Monitor 4K, Pimax Crystal

    • Official Post

    Couple of things you have to consider here

    1) When you set the flight directors to on when on the ground the Boeing autopilot goes to TO/GA in both lateral and vertical modes. They don't disengage when airborne unless you have LNAV, VNAV armed and they engage. This may be a flaw of the real autopilot :)

    2) To get a "clean" autopilot state: Press "V/S" button or ALT HOLD button and HDG SEL button. Alternatively: (AP needs to be off): Set both flight directors to off, then set them back on.

    3) When you move the aircraft from the ground up into the air the aircraft now basically reloads entirely. Everything you have done previously is completely lost. In the future we may change it so that you can move an aircraft to a new location without it being reloaded completely. We may just set flaps up and gear up for you but leave the rest. This was changed in a recent update, I'm not a fan of it either but that is how it is for now. At least it is consistent now.

    4) Some altitude has to be selected in the autopilot. Default would be 10 000ft but if you are flying at 39 k than you have to scroll 290 times. That get's annoying so I synchronize the selected altitude when the aircraft is moved into position.

    5) Speed is synchronized when the aircraft is moved to a new location. Currently it initializes the aircraft at crazy fast speeds but the responsible programmer doesn't hear my concerns. Speed is currently about 290 knots even below 10k, which is far above the 250 kts that would be the maximum speed limit.

    6) Vertical Speed is synchronized as well. When you move the aircraft to a new location on the map the V/S should be 0 ft/min because the aircraft was moved to the new location with 0 ft/min vertical speed. So I don't know how you got 6000 ft/min, that should not happen. That didn't happen to me during testing and trust me, I've tested a lot :) Can you please give me more info on how to reproduce this?

    7) You are flying too fast! Retract the flaps quickly... That happens a lot with the 737 cause it flies like a rocket. Three things we can do about this: increase the mass to a reasonable value, decrease thrust, increase drag.

    My recommendations for the 737:

    - Do not take off with full thrust. That barely happens in the real world. Use about 85% or so

    - To get to a clean autopilot state just press ALT HOLD and HDG SEL. Move the heading bug to your current heading...

    Thank you very much for this extensive answer. I apppreciate this very much.

    I will study your explanations and test them in the sim (good is weekend) and report back. The 737 is a rocket, that is true. I once gave full trust with the parking brake on. When i released it the plane made a vertical takeoff with a tail strike, no need for a runway.

    Thanks again,

    Thomas

    Regards,

    Thomas

    i7-14700KF @ 5.6 GHz, Geforce RTX 4090, 32MB RAM, 1TB SSD M.2, 1TB SSD M.2, 2TB SSD M.2, 32" Monitor 4K, Pimax Crystal

    • Official Post

    I've had those tailstrikes too but never vertical takeoffs. I reduced the thrust for my 737 to a more realistic value. If I can still cruise in high altitude I think we can safely reduce the thrust and make it more flyable that way :) The takeoff is already much easier and you don't need 30° pitch anymore and you're not overspeeding as fast... But we have to test the full spectrum