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Taildraggers  Topic is solved

Controlling your aircraft, using the autopilot etc.

Re: Taildraggers

Postby dilbert » Mon Aug 09, 2021 3:47 pm

Third run: Wheel landed at about 1250 rpm, leaving autopilot engaged. No stick input. Plane bounced a little and ground looped right.
Will try a little flatter touchdown next time, maybe 1400 rpm; and see if plane still ground loops.
Making progress. Will keep playing.
Kind Regards :)
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Re: Taildraggers

Postby dilbert » Mon Aug 09, 2021 4:53 pm

Fourth run:
Soft wheel landing at -50 fps.
Aircraft continued down runway, with tail elevated.
After slowing, it made a gradual turn to the right and left the runway. I did not see the tail lower, but am not sure about that.
Will need to make a few more runs to observe it.

Kind regards. :)
Last edited by dilbert on Sat Aug 28, 2021 12:05 pm, edited 1 time in total.
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Re: Taildraggers

Postby S&J » Mon Aug 09, 2021 5:04 pm

What type of prop is being used ?
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Re: Taildraggers

Postby dilbert » Mon Aug 09, 2021 6:44 pm

Image

Image

Image

Apologize for loss of image-see later posts for retest of images
Last edited by dilbert on Mon Aug 30, 2021 11:34 am, edited 3 times in total.
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Re: Taildraggers

Postby dilbert » Mon Aug 09, 2021 6:47 pm

Too much crosswind right now, will continue later when conditions improve.

All I know about the prop is it's the default version.
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Re: Taildraggers

Postby S&J » Mon Aug 09, 2021 7:46 pm

Ok, it's just that with regards the prop I'm wondering why you're not reducing the blade angle and throttle whilst maintaining rpms.

Low rpm means more torque, doesn't it ?
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Re: Taildraggers

Postby wkitty42 » Mon Aug 09, 2021 9:22 pm

i suspect the tail draggers use fixed pitch props... quite possibly even wooden props ;)
"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: Taildraggers

Postby OO ZVY » Mon Aug 09, 2021 9:24 pm

Tailwheel planes ( YASIM ) can improve with a little toe-out and adjusting cx,cy,cz to increase fuselage lateral drag.

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Re: Taildraggers

Postby dilbert » Mon Aug 09, 2021 10:33 pm

Sorry I missed the Otter. It like the De Havilland DH89 has high stability, and little ground looping tendency.
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Re: Taildraggers

Postby dilbert » Tue Aug 10, 2021 7:53 am

Image

Image

Appeared to turn and leave runway to right with tail still elevated.
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Re: Taildraggers

Postby dilbert » Tue Aug 10, 2021 2:10 pm

Have since tested PA18 on a 36 runway, using HDG in autopilot, with just enough power to take off and set back down.
To me, plane seemed somewhat laterally unstable, and unpredictable as to where it might turn. (might have been my legacy equipment)
Found no indication of any other ground looping tendency.
Kind Regards :)

P.S. Less sure about YASim aircraft, where ground Looping seems prevalent. Will have to test them further.
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Re: Taildraggers

Postby dilbert » Sat Aug 21, 2021 3:36 pm

I used the YASim PA18.

At both 0 and 500 ft, I manually created a 5kt crosswind at 160 degrees.

Here I was established on Nav1 CDI course, and the plane was crabbing about right: the arctan of 5/80 is 3.576, which is about what the plane is crabbing.

Image

Right before touchdown I unchecked Pitch/Altitude Hold, left Heading Control engaged, and manually flared. So why did the plane want to depart the runway to the right :?: The bank is the result of the autopilot trying to keep it on the runway.

Image

The bank was the result of the autopilot trying to use its normal method of correcting headings, which is incorrect for crosswind landings, where you would want right aileron, which creates adverse yaw; and which combined with left rudder, would allow the plane to be steered left.

But that isn't the point. Assume the plane was an old fashioned Ercoupe with castering main wheels. Since the correct crab was well established and the wings level, it would have initially been traveling
straight down the runway after touchdown, while still maintaining its crab. There would have been no turning moment, and further control input would have been unnecessary.

The PA18 isn't an Ercoupe, though still tricycle geared. However, I think its momentum would have initially been straight down the runway at touchdown, and it should not have immediately turned right.

Kind regards
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Re: Taildraggers

Postby dilbert » Sun Aug 22, 2021 12:12 am

Here the plane is approaching the threshold on autopilot, crabbing to compensate for the 5 kt crosswind, and just above touchdown.

Image

Here the autopilot has been released, while the plane is still in flight, and while still maintaining its crab. I have reduced power slightly.
Image
Here the plane has contacted the runway and voluntarily swung right.
Image


Here it is leaving the runway, as I made no control input to restrain it.

Image

Please note the dotted yellow lines on the map, which delineate the progressive amounts of turn.

I see no logical reason for this behavior, as while still in the crab, the plane was already headed directly into its apparent wind, at the moment of touchdown.

Kind Regards

P.S. I deliberately used a tricycle geared plane for these tests, so that the weight would be in front of the main gear.
Last edited by dilbert on Mon Aug 30, 2021 9:19 am, edited 5 times in total.
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Re: Taildraggers

Postby Johan G » Sun Aug 22, 2021 1:06 pm

A post was split off to the new topic Taking off with single engine aircraft without spinning.
Low-level flying — It's all fun and games till someone looses an engine. (Paraphrased from a YouTube video)
Improving the Dassault Mirage F1 (Wiki, Forum, GitLab. Work in slow progress)
Some YouTube videos
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Re: Taildraggers

Postby wkitty42 » Sun Aug 22, 2021 1:10 pm

thanks for moving that while i was responding to it here, johan :lol:
"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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