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Plane Refused to Descend

Controlling your aircraft, using the autopilot etc.

Plane Refused to Descend

Postby Robertfm » Mon Nov 04, 2019 7:47 pm

I was flying PA28 (stock version) VFR approach airport the plane refused to descend even though the stick fully down. The only way I was able to land was to put plane into idle. I took off again and this time used my Yoke sure enough again when I approached a different airport the plane refused to descend. I set the plane to idle and landed.

During this problem I refreshed the Yoke & stick to no avail. The other issue was a drop off in FPM again. No changes in any settings FPM dropped from 60 to around 20. (wasn't AI.

Any ideas
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Re: Plane Refused to Descend

Postby dilbert » Mon Nov 04, 2019 9:19 pm

Not quite sure I follow you.

As the expression goes, Attitude (pitch) controls airspeed and Power controls altitude.

I just flew the PA 18 downwind at a "wingtip's" distance from the runway; reducing power to idle when opposite the threshold, and then made a successful semicircular approach. Not at all abnormal for this sort of light aircraft. (So you used the right technique to bring it down.)

If you lower the nose, rather than decreasing throttle, airspeed will increase; which will, in turn, increase lift, causing the plane to not want to go down.
Which is the reason dive bombers needed airbrakes.

The real question here is, did the nose lower and raise when you moved the yoke forward and back? If not, there is some sort of problem with your controls.

Kind regards
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Re: Plane Refused to Descend

Postby Robertfm » Tue Nov 05, 2019 10:18 am

Apologise if I wasn't clear. Your last sentence was the problem. When it first happened I was using my T16000 stick with it fully forward the plane would not descend and was always trying to ascend. I was at 2000 ft when this happened. I descended by banking and then setting throttle to idol. After landing I changed to my Saitek Yoke took off again and this time the plane was reluctant to gain any altitude climbing at about 100fpm. Once at 1000 feet I again tried an approach and once again the Yoke pushed forward didn't work, so I again set throttle to idol.

I quite FG and reload and then it was fine. I am still having the issue where the generic AP whilst seemingly disconnecting is and has to be 'reconnected' and disconnected again very awkward when within a mile of touch down, although in the above I was VFR.
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Re: Plane Refused to Descend

Postby dilbert » Tue Nov 05, 2019 12:27 pm

In that case, it may be somehow related to use of the generic autopilot-when engaged, it likes to maintain control. Did you try switching off Pitch/Altitude
Control when this happened?
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Re: Plane Refused to Descend

Postby Robertfm » Tue Nov 05, 2019 12:30 pm

As I said at the time I wasn't using it. I was VFR. Are you saying it can interfere when it isn't active. ie not open.
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Re: Plane Refused to Descend

Postby wkitty42 » Tue Nov 05, 2019 2:15 pm

the generic AP is always in some control if any of its boxes are 'X' selected... you have to specifically un-'X' them to turn that part off... it doesn't matter if it is shown on-screen or not...
"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 Refused to Descend

Postby tdammers » Tue Nov 05, 2019 3:24 pm

Robertfm wrote in Tue Nov 05, 2019 12:30 pm:As I said at the time I wasn't using it. I was VFR. Are you saying it can interfere when it isn't active. ie not open.


VFR and autopilot are completely orthogonal. You can use the autopilot while flying under VFR, and you can fly manually under IFR. People do both all the time.
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Re: Plane Refused to Descend

Postby Robertfm » Tue Nov 05, 2019 3:29 pm

wkitty42 wrote in Tue Nov 05, 2019 2:15 pm:the generic AP is always in some control if any of its boxes are 'X' selected... you have to specifically un-'X' them to turn that part off... it doesn't matter if it is shown on-screen or not...


But you can't completely remove the X's in each section 1 will remain with an X unless I am doing something wrong.
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Re: Plane Refused to Descend

Postby Robertfm » Tue Nov 05, 2019 3:31 pm

tdammers wrote in Tue Nov 05, 2019 3:24 pm:
Robertfm wrote in Tue Nov 05, 2019 12:30 pm:As I said at the time I wasn't using it. I was VFR. Are you saying it can interfere when it isn't active. ie not open.


VFR and autopilot are completely orthogonal. You can use the autopilot while flying under VFR, and you can fly manually under IFR. People do both all the time.


I realise that but I wasn't using it.
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Re: Plane Refused to Descend

Postby dilbert » Tue Nov 05, 2019 3:58 pm

There are a few differences between the FG Autopilot/Route Manager system and the real thing.

The primary difference is that in a real system manual movement of the controls disengages the autopilot automatically, which is not the case with the generic system: you have to uncheck either or both the Heading Control and Pitch/Altitude boxes, using the autopilot menu, depending on which feature or features you wish to resume manual control of. :)

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Re: Plane Refused to Descend

Postby Robertfm » Tue Nov 05, 2019 4:11 pm

I get that, perhaps something was still connected I will bare that in mind if it happens again.
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Re: Plane Refused to Descend

Postby wkitty42 » Tue Nov 05, 2019 4:48 pm

Robertfm wrote in Tue Nov 05, 2019 3:29 pm:
wkitty42 wrote in Tue Nov 05, 2019 2:15 pm:the generic AP is always in some control if any of its boxes are 'X' selected... you have to specifically un-'X' them to turn that part off... it doesn't matter if it is shown on-screen or not...


But you can't completely remove the X's in each section 1 will remain with an X unless I am doing something wrong.

i don't know why not... but i use it all the time with the UFO... but there may be something in the craft you are flying that is causing that to happen like that... it is possible that there's a switch in the craft that is flipping the GAP parts back on when you try to turn them off via the F11 dialog... i don't know... i'll have to look back and see if i can find the craft you are using...
"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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