Board index FlightGear Development Aircraft Autopilot and route manager

Boeing 777 autopilot problem

Designing a stable autopilot is one of the hardest things. Need help?

Boeing 777 autopilot problem

Postby Mihajlo » Tue Jun 18, 2019 7:12 pm

I often encounter a problem with an autopilot where it won't turn on as it immediately disengages when I try to turn it on. It doesn't always happen and I don't think I'm doing anything differently, so I don't have a reliable way to reproduce it. This didn't happen before and I know there have been a lot of changes to 777 recently. I'm using the latest version from FGAddon. FG version is 2019.2.0 build 3394. Here is an error message I get in a nasal console: https://ibb.co/XzwN5g3
Mihajlo
 
Posts: 54
Joined: Tue Aug 28, 2018 6:47 pm

Re: Boeing 777 autopilot problem

Postby legoboyvdlp » Tue Jun 18, 2019 7:23 pm

You need to (like almost every airliner) have no flight control input when you engage autopilot. You can use the trim speed to maintain level flight and then engage autopilot when you have no input, or else release flight controls and immediately engage it.
User avatar
legoboyvdlp
 
Posts: 7981
Joined: Sat Jul 26, 2014 2:28 am
Location: Northern Ireland
Callsign: G-LEGO
Version: next
OS: Windows 10 HP

Re: Boeing 777 autopilot problem

Postby Mihajlo » Tue Jun 18, 2019 8:21 pm

Okay, thanks.
Mihajlo
 
Posts: 54
Joined: Tue Aug 28, 2018 6:47 pm

Re: Boeing 777 autopilot problem

Postby Octal450 » Tue Jun 18, 2019 10:01 pm

Also -- don't use V/S, use FLCH. It will give you proper climb rates/descent rates for your selected speed automatically using speed by pitch.

Kind Regards,
Josh
Skillset: JSBsim Flight Dynamics, Systems, Canvas, Autoflight/Control, Instrumentation, Animations
Aircraft: A320-family, MD-11, MD-80, Contribs in a few others

Octal450's GitHub|Launcher Catalog
|Airbus Dev Discord|Octal450 Hangar Dev Discord
User avatar
Octal450
 
Posts: 5583
Joined: Tue Oct 06, 2015 1:51 pm
Location: Huntsville, AL
Callsign: WTF411
Version: next
OS: Windows 11

Re: Boeing 777 autopilot problem

Postby Isaak » Tue Jun 18, 2019 10:18 pm

Hi there, thanks for the feedback! The listener errors you get were already present before, you just didn't see them because they weren't logged. Richard has changed something in the core code so they are shown. I 'll try to find where the listeners are called and replace them.
Want to support medical research with your pc? Start Folding at Home and join team FlightGear!
Isaak
 
Posts: 768
Joined: Sat Jun 04, 2011 3:52 pm
Location: Hamme, Belgium
Pronouns: he, him
Callsign: OO-ISA
Version: next
OS: Windows 10

Re: Boeing 777 autopilot problem

Postby Mihajlo » Thu Jun 20, 2019 8:57 am

You are welcome. Thanks for the tip. I'm glad you've decided to maintain and improve this aircraft. It was unmaintained for a long time without any improvements.
Mihajlo
 
Posts: 54
Joined: Tue Aug 28, 2018 6:47 pm

Re: Boeing 777 autopilot problem

Postby Octal450 » Thu Jun 20, 2019 3:25 pm

Enjoy :D

Josh
Skillset: JSBsim Flight Dynamics, Systems, Canvas, Autoflight/Control, Instrumentation, Animations
Aircraft: A320-family, MD-11, MD-80, Contribs in a few others

Octal450's GitHub|Launcher Catalog
|Airbus Dev Discord|Octal450 Hangar Dev Discord
User avatar
Octal450
 
Posts: 5583
Joined: Tue Oct 06, 2015 1:51 pm
Location: Huntsville, AL
Callsign: WTF411
Version: next
OS: Windows 11

Re: Boeing 777 autopilot problem

Postby powerwagon24 » Wed Dec 02, 2020 4:25 pm

Can anyone walk me through how to use it. I have figured out how to use the auto throttle but not much else. I enabled the hold heading button in the 777 but it just twitches at the yoke or just keeps turning the way I left it. I was using the keyboard to control it previously and I heard that you're not supposed to control it but I don't know how to do that. Please help. Thanks, guys.
powerwagon24
 
Posts: 1
Joined: Wed Dec 02, 2020 4:18 pm

Re: Boeing 777 autopilot problem

Postby Isaak » Wed Dec 02, 2020 9:14 pm

Make sure to have your controls (close to) centered when you engage the autopilot, otherwise it will deactivate immediately, as in real life. The autopilot will engage in the mode you programmed it. If nothing was prepared, it will do this:
- Lateral: keep the heading if the wings were level (horizontal) during activation, or keep the bank angle the aircraft flew at during engagement (Attitude mode).
- Vertical: keep the current vertical speed.

Use the in cockpit buttons to operate the autopilot. You can use the gui dialog (F11), but that's much less intuitive.

For all modes:
- Left button: press/select
- scroll wheel: rotate a rotary knob to change the value in the dialog above/next to it.
I think you can use middle/right click too if you don't have a scroll wheel, but I should check.

Vertical modes:
- FLCH: flight level change: fastest way to reach a new flight level/altitude. First set the desired altitude in the altitude box (on the right), then press FLCH. It will command idle thrust to decend and climb thrust to climb. Then the autopilot will modify vertical speed to keep the current airspeed until the new FL/alt is reached, after which Alt Hold is enabled.
- VS: Use this to climb/descend to a new flight level/altitude at a fixed vertical speed until the new FL/alt is reached, after which Alt Hold is enabled. Caution: if the VS is too high (or too low): the airplane might not be able to hold the current airspeed because it can't provide enough thrust or drag. Set the desired VS by scrolling on the wheel. The mode will engage automatically as soon as you do this.
- Altitude hold: speaks for itself. Press the hold button at any time to stop an active climb/descent and level off at the current alt/lvl. Rarely used as it can command a quite abrupt change in vertical speed and will only be used in imminent dangerous situations.
VNAV: automatic mode that will follow the flight plan. It's not yet fully implemented, but can do step climbs as entered in the Route Manager and calculate and perform a descent towards an airport. Cruise descent is not implemented and should be performed with either FLCH or VS.
- App (see lateral)

Lateral modes:
- Heading/track hold: select the desired heading/course by turning the rotary knob with your scroll wheel (you can switch between heading and track with the tiny button above the rotary knob). Then click the rotary knob with your left mouse button. The aircraft will command HDG SEL on the PFD and turn towards the new heading via the shortest possible turn (left/right) => if you have to make a >180° turn, make sure that you don't scroll too fast, or the aircraft will change direction as soon as you pass its 6 o' clock position.
- Loc: keep the current lateral mode until intercepting the selected ILS localiser. Then follow that ILS to the runway. This won't work for VOR's, as that is done via the CDU in real life. Make sure not activate this mode unless within reach of the selected localiser (most of the time 15 Nm in FG).
- App: lateral: see Loc. Vertical: only after the loc has been intercepted: maintain current altitude mode (VS/FLCH/Alt Hold/VNAV) until intercepting the glide slope. Then intercept it and follow the glide slope down towards the runway. When this mode is used, the aircraft is capable of autolandings on runways equiped with an ILS. If the ILS has the same frequency for both directions of the runway: the rollout phase will most likely fail because the aircraft receives mixed or no signal: so use caution and only perform autolandings on suitable runways.

Thrust:
- In FLCH and VNAV modes, the autopilot sets thrust based on the mode it is in (takeoff/climb/idle). In FLCH mode the autopilot will try to maintain the selected airspeed by pitching the aircraft up or down. In VNAV mode the speed dialog will be blanked ("managed") and the autothrottle or autopilot will maintain speed depending on the current flight phase. During descent you can override the managed speed by left clicking the speed rotary knob and selecting an other speed. The autopilot will stay in VNAV mode, but without managed speeds (you 'll need to set these manually until left clicking the speed knob again).
- In all other modes Thrust is set directly by selecting a speed in the speed dialog (scroll the rotary button). It works like cruise control in a car.

I hope this clarifies a bit? I've written this out the top of my head, so please ask if I 've forgotten something.
Want to support medical research with your pc? Start Folding at Home and join team FlightGear!
Isaak
 
Posts: 768
Joined: Sat Jun 04, 2011 3:52 pm
Location: Hamme, Belgium
Pronouns: he, him
Callsign: OO-ISA
Version: next
OS: Windows 10


Return to Autopilot and route manager

Who is online

Users browsing this forum: No registered users and 0 guests