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plane crashes after take off

Controlling your aircraft, using the autopilot etc.

Re: plane crashes after take off

Postby wlbragg » Sat Jan 26, 2019 5:12 pm

dilbert wrote in Sat Jan 26, 2019 4:41 pm:The real 172 had a flimsy little lever that fitted in a saw-toothed detente beneath the panel, which adjusted rudder trim.

We've added an optional, in cockpit rudder trim. So that is available. I don't know if it is in fgdata yet or not.

As far as OP issue and cause, yes we need a little more info.

The joy stick and controls work perfectly after the engine is started automatically. Take off goes as expected. Then, 10 or 15 seconds after lift off, the plan banks hard to the left and crashes.

A stall in the c172p as programed would lead to the description of the OP no matter what they do with the control surfaces. So it is a quick check to make sure it isn't a simple pilot error mistake.
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Re: plane crashes after take off

Postby ccomley » Sat Jan 26, 2019 5:56 pm

Having similar fun!

Brand new user, trying out FG with a Thrustmaster hotas X.

Windows 7
NO changes made to base settings except for picking up the joystick, which it recognises. I went into the config page for that and confirmed it could see all the movement, centered up, then picked a couple of buttons for flaps up and down. Tweaked it to use the HOTAS throttle as throttle (odd that wasn't the default - is the TM-x also available as stick-only?) Set up the hat switch to do rudder and elevator trim.

Autostart, take-off, as mentioned above, it keeps rolling out to the right. Doesn't matter if I start in mid air. It can be controlled but needs a large input. Surely can't be right?
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Re: plane crashes after take off

Postby wkitty42 » Sat Jan 26, 2019 6:42 pm

dilbert wrote in Sat Jan 26, 2019 2:45 pm:First, it would be helpful if Icoon0 would provide hardware, operating system, FG version, and type stick so we can figure out what's going on.

i started to suggest that, too, but we're not in the support area where these types of reports should be made... at least the pink box is at the top of those areas over there ;)
Last edited by wkitty42 on Sat Jan 26, 2019 6:46 pm, edited 1 time in total.
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: plane crashes after take off

Postby wkitty42 » Sat Jan 26, 2019 6:44 pm

dilbert wrote in Sat Jan 26, 2019 4:41 pm:P.S. According to my 25 year plus recollection, The real 172 had a flimsy little lever that fitted in a saw-toothed detente beneath the panel, which adjusted rudder trim.

this is now modeled and active in the FG c172p... it wasn't at one time but it has been in the last month or two, IIRC...
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: plane crashes after take off

Postby wkitty42 » Sat Jan 26, 2019 6:46 pm

ccomley wrote in Sat Jan 26, 2019 5:56 pm:Autostart, take-off, as mentioned above, it keeps rolling out to the right. Doesn't matter if I start in mid air. It can be controlled but needs a large input. Surely can't be right?

rolling to the right? you have something set up incorrectly... the roll of the c172p at lift off, with no counter actions, is to the left... sounds like you have too much aileron trim set...
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: plane crashes after take off

Postby legoboyvdlp » Sat Jan 26, 2019 9:35 pm

The c172p does not have any aileron trim control set up and there is no key binding for that anyway, so it's difficult to see how a user could change aileron trim without delving into the property browser.
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Re: plane crashes after take off

Postby Alant » Sat Jan 26, 2019 10:12 pm

Could you do a test flight using the keypad or mouse instead of the joystick? See sections 4.3 and 4.4 of http://www.flightgear.org/Docs/getstart ... rtch4.html.

It will be easier if you do an in-air start.

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Re: plane crashes after take off

Postby Parnikkapore » Sun Jan 27, 2019 12:20 am

wkitty42 wrote in Sat Jan 26, 2019 6:46 pm:rolling to the right? you have something set up incorrectly... the roll of the c172p at lift off, with no counter actions, is to the left...


It does sometimes p-factor to the right for me, probably in relation to the wind. Just after takeoff is always a nightmare, but I can get it into stable flight within 3 seconds.

OP: Yes, try pressing TAB and flying the plane with the mouse with the stick disconnected, so we know if a buggy joystick config is an issue.
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Re: plane crashes after take off

Postby wkitty42 » Sun Jan 27, 2019 5:48 pm

Parnikkapore wrote in Sun Jan 27, 2019 12:20 am:
wkitty42 wrote in Sat Jan 26, 2019 6:46 pm:rolling to the right? you have something set up incorrectly... the roll of the c172p at lift off, with no counter actions, is to the left...


It does sometimes p-factor to the right for me, probably in relation to the wind.

that wouldn't be p-factor, then...

Parnikkapore wrote in Sun Jan 27, 2019 12:20 am:Just after takeoff is always a nightmare, but I can get it into stable flight within 3 seconds.

that's why i tend to ""cheat"" and get the AP set up first before takeoff... then once i'm airborne i immediately turn on the AP which levels the wings and holds the current climb rate... then i adjust the climb rate to something the c172p can actually handle... 700fpm or less to start with at full power and then i turn down the climb rate as we gain altitude... from there i either stick with the AP and use the heading bug to steer or i may turn off the AP and try flying by hand... this is how i was able to hit max ceiling in the testing i've done ;)
Last edited by wkitty42 on Sun Jan 27, 2019 5:52 pm, edited 1 time in total.
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: plane crashes after take off

Postby wkitty42 » Sun Jan 27, 2019 5:51 pm

legoboyvdlp wrote in Sat Jan 26, 2019 9:35 pm:The c172p does not have any aileron trim control set up and there is no key binding for that anyway, so it's difficult to see how a user could change aileron trim without delving into the property browser.

you are right... i had thought there was something for the ailerons added recently but i guess that was the rudder trim...
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: plane crashes after take off

Postby legoboyvdlp » Sun Jan 27, 2019 5:57 pm

Uh - not sure if anything is different in the 2018.3 version compared to the GitHub version fdm but I don't see anything like what parnikkapore or ccomely is describing. All I can think of is load and balance: maybe you have a copilot and passenger in the right hand back seat?


Also as long as I center rudder immediately after takeoff and use it to try and maintain centreline I also have no problems with it trying to kill me in the first three seconds after takeoff.

Maybe you are using old versions of the C172 that had oversensitive fdms: so:



Ccomely, parnikkapore and OP: what version of FlightGear are you using and are you using the c172p that came with your version (not another one that you got someplace else?)
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Re: plane crashes after take off

Postby Alant » Sun Jan 27, 2019 9:25 pm

The C172 is the default aircraft, and the forum is not flooded with problems such as this. This means that we have to try and discover what has gone wrong with your installation.

Could you please let us know as much as possible about your system. Especially Windows version, Flightgear version, where you downloaded Flightgear from and how you installed it.

Are you using the default C172 that comes with Flightgear, or have you installed a different version?

Thanks.

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Re: plane crashes after take off

Postby Parnikkapore » Mon Jan 28, 2019 12:23 am

FlightGear 2018.3.1 from Saiarcot's PPA, Bionic, Default c172.

To be clear, the "rightwards P-factor" only happens from time to time, and I believe it might've been windvaning-related effects. (Needs more testing)

The "post-takeoff hell" is only the aircraft banking towards the rudder heading at takeoff, which it totally should and doesn't come close to deadly. It's easy to correct.
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Re: plane crashes after take off

Postby dilbert » Mon Jan 28, 2019 12:52 pm

Icoon0,

The elevator trim wheel is below the center of the panel. It will display it's setting when rotated. Set it at around
.14 nose down. For some reason, the take-off setting leads to an excessive nose up attitude. Hope this helps.
Best Regards :)

P.S. Be sure to adjust the trim after Autostart, as Autostart seems to reset trim to it's original take-off position.
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Re: plane crashes after take off

Postby AMM » Sun Mar 03, 2019 10:43 am

in my case the Cessna starts going to the left during take off while on the runaway. The joystick works well. It is calibrated, the rudder is centred and yet it goes to the left. Any ideas how to fix this?
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