Can the front Wheel Spat cause Yaw?

[BirdDog]

So here is  question - put your thinking caps on....

 

If the front wheel of an LSA is not aligned - OR - the wheel spat is not aligned, could it cause the rudder to to deflect and cause a yaw response?

 

Let's discuss!

[FlyBoy1960]

Yes of course, It's like a huge trim tab but at the front of the aircraft rather than the back.

 

I remember reading about some very fast aircraft in the US that with the flow without wheel pants even though it is a requirement of the manufacturer. On rare occasions the wind would catch the front wheel doing 150 kn and turn it to the maximum limit instantly. It caused some of the doors to blow in on the aircraft and people actually got hurt because the heads hit the doors or reach other. The response was extremely violent.

 

I will see if I can find the article, it was on the EAA website

[BirdDog]

Yeah cool.

 

I knew this is the case, but want to open it to discussion.  

I am having some issues with yaw affects, which I have narrowed down to a combination of wheel spat, and too much play in the rudder.  The rudder is about to be tensioned, and then I will get on to the spat. Amazing the affect it can have.

[Thruster88]

Also check the pretension on the nosewheel pivot. There should be a spec in the maintenance manual.  This is important especially for free castoring types like RV's to reduce the risk of shimmy.

[BirdDog]

Yeah thanks man!  Mine is a steerable wheel.  

[Thruster88]

It may still have a pretension spec or it could be binding making the rudder hold a small deflection.  

[440032]

Rutan Defiant had no conventional rudders, just a single forward mounted rudder under the nose.

[Flightrite]

Spats generally have more area behind the pivot line so they 'trail' & therefore designed not to weathercock.

Edited August 16, 2021 by Flightrite

[FlyBoy1960]

I think you mean they are designed to whether cock ?

[Flightrite]

true, slip of the keyboard tongue:-)

[BirdDog]

Yep!  And that weather cock can pull the rudder around if not aligned.

[skippydiesel]

Just had a random thought - this would only work (if at all) for a steerable nose wheel set up - if you wanted to apply a small amount of rudder trim. This could be archived by rigging the rudder/nose wheel alignment so as to apply the trim, thus removing any need for a fixed trim tab.

[BirdDog]

7 minutes ago, skippydiesel said:

Just had a random thought - this would only work (if at all) for a steerable nose wheel set up - if you wanted to apply a small amount of rudder trim. This could be archived by rigging the rudder/nose wheel alignment so as to apply the trim, thus removing any need for a fixed trim tab.

 

My bird actually does not even have a trim tab.  So it's essential everything is aligned.  I wished it did.  My last bird did, and it made life easier, let me tell you!

 

[facthunter]

If your engine is in the usual place,  power setting must affect it. Nev

 

[FlyBoy1960]

??   What is the "usual place"

[Yenn]

I suppose the answer is Yes, but you should be using your feet to control the rudder, not letting it and the nosewheel do whatever they like.

Are you flying the plane or just going along for the ride?

[FlyBoy1960]

21 minutes ago, Yenn said:

I suppose the answer is Yes, but you should be using your feet to control the rudder, not letting it and the nosewheel do whatever they like.

Are you flying the plane or just going along for the ride?

 

the report that I read was that the movement was so aggressive no amount off force on your feet could stop the rudder moving

[skippydiesel]

1 hour ago, Yenn said:

I suppose the answer is Yes, but you should be using your feet to control the rudder, not letting it and the nosewheel do whatever they like.

Are you flying the plane or just going along for the ride?

Come on Yenn, "dont come the raw prawn" - many aircraft (probably all GA & above) have one or both longitudinal & lateral trim. Trim can be pilot adjusted (in the air) and or fixed. The latter is usually a small metal tab, fixed to the trailing edge of the control surface that the pilot feels needs some "help", that can be adjusted by bending more /less to get the desired effect. Whatever system is used the desired outcome is a a centralised/light control at given air speed & aircraft load.

Edited August 17, 2021 by skippydiesel

[Yenn]

What report was that. I haven't seen one and was just responding to the question.

[RFguy]

what's the tendency to yaw say at 50, 70, 85 , 100% power etc ?  

any springs holding the rudder (pedals, wheel) centred? ) spring fallen off ? (happens in Jabiru's with big boots on ) 

 

[skippydiesel]

2 hours ago, RFguy said:

what's the tendency to yaw say at 50, 70, 85 , 100% power etc ?  

any springs holding the rudder (pedals, wheel) centred? ) spring fallen off ? (happens in Jabiru's with big boots on ) 

 

Tendency to yawn when your big booted spring falls off????🙂

[BirdDog]

2 hours ago, RFguy said:

what's the tendency to yaw say at 50, 70, 85 , 100% power etc ?  

any springs holding the rudder (pedals, wheel) centred? ) spring fallen off ? (happens in Jabiru's with big boots on ) 

 

 

I have been doing some investigations and I have a combination of things.

Firstly, it will do it more when under full power.  If I back off and let it glide, the effect is much less.  

I have already aligned the wheel, but have discovered a little too much play in the rudder, which I am rectifying.   I am of the belief that I have had the effect of both an unaligned front wheel (The LAME had replaced the rudder steering cable at the last 100) and the play in the rudder.

 

When applying full power there is a noticeable yaw to the left, and I believe this is the play in the rudder where the prop wash is forcing the rudder left.

 

I have never pushed on the control surfaces during the daily (especially when the sticker says "Don't Push") so it has gone unnoticed.  I would have picked it up on the next 100, but I might change the way I do things from this point.

 

 

 

[Jabiru7252]

I would assume the nose wheel and the rudder can be adjusted independently of each other. So, disregarding the rudder, adjust your nosewheel so you taxi straight ahead with the pedals neutral. Once you're happy with that, adjust your rudder so that at cruise power there is no yaw. Remember, maladjusted ailerons or flaps will cause a yaw, but with roll. Under high power, a yaw to the left is normal, under a glide, yaw to the right is normal. Remember when your instructor kept yelling "MORE RIGHT RUDDER!!!" as you gunned it down the runway during those first few hours.

Edited August 18, 2021 by Jabiru7252

[BirdDog]

6 minutes ago, Jabiru7252 said:

I would assume the nose wheel and the rudder can be adjusted independently of each other. So, disregarding the rudder, adjust your nosewheel so you taxi straight ahead with the pedals neutral. Once you're happy with that, adjust your rudder so that at cruise power there is no yaw. Remember, maladjusted ailerons or flaps will cause a yaw, but with roll. Under high power, a yaw to the left is normal, under a glide, yaw to the right is normal. Remember when your instructor kept yelling "MORE RIGHT RUDDER!!!" as you gunned it down the runway during those first few hours.

Yes! They are independent of each other.  A lot of the right rudder will be from the torque from the donk.  You should not have to be leaning on the right rudder in the cruise.

I cruise at about 90% full noise, with prop thickened to sit at about 5200.

[Flightrite]

The "don't push" (or words to that effect)  has nothing to do with checking control surface movement by hand, not very clever never checking them at pre-flight!

Edited August 18, 2021 by Flightrite