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Flite Test Pietenpol won't run straight...

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Foxfan18/09/2019 18:25:36
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824 forum posts
6 photos

Hi, I have a Flite test Pietenpol which has flown beautifully in the hands of an old, skilled club member who enjoyed it, but when I tried to do some taxi tests it

a) wouldn't move on grass, just tipped up and

b) on pavement just turned left immediately despite right thrust built in .

Any suggestions? Apart from hand launch of course. I was looking for something I could practice on my own with it, especially in the absolute calm of this lovely evening.

Martin

Ron Gray18/09/2019 18:36:12
1446 forum posts
363 photos

The rudder is your friend!

J D 818/09/2019 19:06:25
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1253 forum posts
74 photos

Most aircraft of this type [ tail dragger with wheels ahead of centre of gravity ] Will tend to diverge when starting the take off roll. Open the throttle slowly and be ready to correct any swerve with rudder.

Also hold in up elevator until the aircraft starts rolling along the ground easing off as speed is gained [ You must not have much up in as it leaves the ground ] This does two things in that it prevents nose overs and holding the tail wheel/skid on the ground helps it steer straight until the air surfaces take control.

On some aircraft rudder is not very effective until the tail is raised and the take off roll is well under way.

Many aircraft of this type like to take off directly into wind and if you don't do it the plane will turn into wind itself.

Hoe this helps. John.

Don Fry18/09/2019 20:14:33
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3910 forum posts
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Double post tremor.

Edited By Don Fry on 18/09/2019 20:17:41

Don Fry18/09/2019 20:14:34
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3910 forum posts
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A tail dragged has, with a counter clockwise prop, two forces screwing it to the left when you start the roll from stationary.

The first, is procession, the propellor, acting as a gyroscope, is pulled forward, out of line from its direction of travel. And it screws the aircraft to the left.

The second is torque.

The first disappears when you get the tail up. But until you get the tail up, and get some speed, the rudder does not work, and blast the motor open, to get wind past the rudder, and the torque does you.

The solution.

Up elevator. Advance the throttle, not slam, a lot of right rudder, let go of up elevator, the tail rises. And less rudder, as procession goes away. As it accelerates, the rudder comes off. Ease back elevator, and it's an aircraft.

Getting a tail dragger up is an art. And is easier if you don't apply too much power. Because the two screwing forces, procession and force, both increase if you use your available power.

But to do that, you have to be happy to fly close to the ground, then you don't have to use power to do the scalded cat take off.

Tom Sharp 218/09/2019 21:28:25
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3514 forum posts
18 photos

Oil your wheel bearings. laugh

Foxfan18/09/2019 22:42:37
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824 forum posts
6 photos

Thanks gents. As I don't have a concrete strip I'm stuck because even with careful increasing of throttle there comes a point where the thing just pops over on its nose, having gone nowhere at all. I guess it's the weight, or extreme lack of it.

Don and John, thanks for the info on take-offs. I also have my big heavy DB Mascot, so I'll use your advice with that.

Meanwhile I think I will do a fairly radical mod. to the wee Piet, by taking the u/c off altogether and fitting it with landing skids made of aluminium Tig welding rod. The general consensus is that a hand launch is essential with these tiddlers if all you have is grass, however well cut. And the moment the wheels touch, even on a greaser,the thing stops dead, which buckles fairings and bends u/c wire.

Martin

Don Fry19/09/2019 06:47:25
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3910 forum posts
42 photos

Fit bigger wheels? HobbyKing do big hollow spoke jobs, very light.

Build a catapult/elastic launch frame. Can fit foot operated release pedals. Make from water pipe?

Denis Watkins19/09/2019 07:14:23
3875 forum posts
58 photos

I too would keep the undercarriage,

Simply to protect the underside from mud, water and damage

It is a way forward to practice rise off ground properly

Piers Bowlan19/09/2019 08:39:17
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1868 forum posts
44 photos

Yes, bigger wheels (and shorter grass!). yes Also, raking the undercarriage forward a bit will help.

The third thing that causes yaw on take off (or at any time) is slipstream effect. The rotating wash from the propeller impinging asymmetrically on the fin and rudder.

Edited By Piers Bowlan on 19/09/2019 08:43:19

Foxfan19/09/2019 09:06:09
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824 forum posts
6 photos

How big would the wheels need to be? Without it looking really odd. I think its light weight is a problem where taxying is concerned. The grass is what ever the grass cutter man makes it. The field is nice and flat, but so is my lawn and it just tipped up immediately. It was practice for rise of ground that I was trying to do, Dennis, but no chance.

Don, there's no way I could cart a launch frame about in my little car! I've seen them on youtube.

Martin

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