[Capflyer]

One of the dramatic differences I have found from my RV7 to my RV4 is the heavier stick forces. In my -7, regardless of speed or attitude, the stick was always light in force in any direction. In my -4, I find that the ailerons are somewhat heavy but especially the elevators when speed picks up over 150kts. While doing my panel upgrade and autopilot servo install, the entire interior was removed and I inspected all the control systems and everything was fine so I doubt highly it is a mechanical malfunction. The elevator is balanced.

Any suggestions why I have this or is it normal in the RV4 to have such heavy ailerons at higher speeds?

 

[pierre smith]

Hi Mike..

...my buddy cut his stick quite a bit shorter than the plans and also has higher stick forces on his -4, than my -6.

Check to see that your ailerons are aligned with the airfoil...if they 'droop', you'll have higher aileron stick forces as well, since they're down in the high pressure realm. Check your stick length as well.

IIRC, the bend radius on your ailerons' trailing edge has an effect on stick forces....hopefully someone else will chime in here,

Best,

 

[airbal]

air

the most likely cause of heavy stick forces on the rv-4 vs the 7 is CG. if you are flying the rv-4 solo, cg is farther forward than on the 7. my rv-8 is very nose heavy and quite noticeably higher stick forces than my 7.

warren

 

[Dmadd]

the faster I go, the heavier the stick forces get. Thats good..no?

Dm
RV-4

 

[Rick RV-4]

Check the trailing edges

I'm with Pierre, I'd check the trailing edge bends on the ailerons first before anything else.

Rick

 

[rocketbob]

You can change the ratio on the elevator bellcrank to get lighter stick forces in exchange for increased stick travel, by fabricating a new bellcrank that is shorter above the pivot bearing. I came up with this idea for the F1's and several builders have implemented it. I've flown rockets with this mod and it gives a much nicer feel in pitch. The RV-7 has a 1:1 ratio at the aileron bellcrank where the older non-prepunched RV's have a different ratio. I worked with a friend of mine to change the ratio on the aileron bellcranks on an RV-3B wing and it worked wonders. He cut the weldment so it had a shorter arm from the pushrod going to the stick. The TE thickness definitely has an effect but once the control surfaces are built there is only a little bit that can be done to widen them without risking oil canning.

 

[REHughes]

Aileron Forces

... I worked with a friend of mine to change the ratio on the aileron bellcranks on an RV-3B wing and it worked wonders. He cut the weldment so it had a shorter arm from the pushrod going to the stick. .

I believe that to lighten the Lateral stick forces, you need to shorten the bellcrank arm that drives the pushrod to the aileron horn, rather than the way you described it above.

An evaluation of the available Lateral stick travel in the cockpit, particularly for individuals with big legs, must be performed carefully, to ensure that full aileron travel can be achieved with any modification to the bellcrank geometry.

As an aside to the discussion of elevator stick forces, I seem to remember that the small-tail Lancairs suffered with too-light elevator forces, and the problem was addressed with good results by shortening the elevator horn distance by 5/8" or so.

 

[rocketbob]

I didn't describe it well...the bellcrank arm in the wing was shortened on the arm going to the aileron pushrod.

 

[Sid Lambert]

The RV-4 stick forces are much higher when solo. When you put someone in the back it will feel more like a -6 or -7.

4 G's at 180 MPH takes a good bit of force in a nose heavy -4.

 

[Capflyer]

Good information guys...thanks. Sounds like overall this is normal.

The ailerons are lined up perfectly with the airfoil. As to the trailing edge bend radius, it looks pretty typical similar to what I see on other RV's. A more aft CG helps some but not the solution. Changing the bell crank might be something to take a hard look at. My stick length is fine, it comes right to the bottom of my panel which is the standard panel, not lowered.

Over the weekend I was sitting right seat in a -7 and when I took the stick I was initially over-controlling the plane because I am so used to the higher stick forces now. It was simple to control with one finger on top just like mine was.