jcmcdowell
Well Known Member
I bought the RV7 and had my 'test' pilot (insurance pilot) flew it back from LA (lower Alabama) and he commented on the heavy wing. He said there was about 10lbs of pressure required at cruise to maintain level flight and the roll was VERY pronounced without the correction.
We got her back into the hangar and started all the usual inspections to work it out.
1. Electric Aileron trim- the previous owner 'tightened' the springs to increase the forces, all it did was stiffen the controls. (undid springs for testing)
2. check aileron hinges, alignment- (less than a 1/4" difference)
3. check fairings, noticeably wingtip rise/droop (ok- not enought to cause 10lbs of force on the stick)
measure, measure, measure, test test test
Finally, I was speaking to a RV8 builder on a hangar saturday and recounted my experience and he spoke of a similar problem.
NOW BEFORE THERE IS A LOT OF FLACK;
1. I consulted multiple builders, AP, tech advisors
2. Multiple qualified Eyes visually inspected
3. CFI, tech advisor, AP- rode with me on the test flight
Ok- on with the show;
The RV8 builder suggested RV's are still homebuilt airplanes despite the quality of the kits there will be variation from one to another in construction. There can be slight 'inequalities' that are not noticeable and immeassurable (we hate to use the word 'twist') that can affect the subtle characteristics without adversely affecting the quality of construction.
Or more coarsely, As this gentleman said- All RV's are 'off' in some way or another- you just don't know it. After going through all the same dignostics- his fix was to adjust the leading edge of the vertical stabilizer in the opposite direction of the heavy wing.
After inspection/consultation- I moved the leading edge of my vert. stab on my RV7 1/4" to the right (heavy left wing) which 'in theory' placed it on the centerline (there is a 1/4" joggle built in). We re-attached the fairing with 4 screws temporarily (some work required to re-do that fairing permanently, didn't want to screw it up if it didn't have any effect).
We took a test flight and got her up to cruise and the ball was centered and almost ALL the heavy wing was removed. To the point that, some Aileron alignment and subtle tweaking can fix the rest of the issue.
My theory- there's a LOT of variables on the plane.
Could there be 1/4" twist in the fuse over the entire lentgh, creating an inability to measure a true centerline without significantly affecting quality- sure.
Could the specific prop and engine combo affect the amount of P force and contribute- sure
In summary, if you have a heavy wing- in level flight check the ball. If you are flying level (counteracting the heavy wing) and it's like walking around with a 10lb weight outstretched and the ball is out, A significant culprit may lie in the vertical stabilizer leading edge.
It took less than an hour to get the fairing off, move the leading edge, install some temporary bolts (similar to the permanent bolts specified) and temporarily re-install (not beautiful but on) the fairing for a test flight.
A permanent fix is to make a new doubler plate that is riveted to the fore support and bolted to the horizontal stab. Use the same holes in the horizontal stab angles and use the same holes in the vertical stab (back drilling). You're left with a few extra AN-3 lightening holes in the flat stock of the fore spar of the horizontal stab (don't temporary drill through angle stock- it's structural).
We got her back into the hangar and started all the usual inspections to work it out.
1. Electric Aileron trim- the previous owner 'tightened' the springs to increase the forces, all it did was stiffen the controls. (undid springs for testing)
2. check aileron hinges, alignment- (less than a 1/4" difference)
3. check fairings, noticeably wingtip rise/droop (ok- not enought to cause 10lbs of force on the stick)
measure, measure, measure, test test test
Finally, I was speaking to a RV8 builder on a hangar saturday and recounted my experience and he spoke of a similar problem.
NOW BEFORE THERE IS A LOT OF FLACK;
1. I consulted multiple builders, AP, tech advisors
2. Multiple qualified Eyes visually inspected
3. CFI, tech advisor, AP- rode with me on the test flight
Ok- on with the show;
The RV8 builder suggested RV's are still homebuilt airplanes despite the quality of the kits there will be variation from one to another in construction. There can be slight 'inequalities' that are not noticeable and immeassurable (we hate to use the word 'twist') that can affect the subtle characteristics without adversely affecting the quality of construction.
Or more coarsely, As this gentleman said- All RV's are 'off' in some way or another- you just don't know it. After going through all the same dignostics- his fix was to adjust the leading edge of the vertical stabilizer in the opposite direction of the heavy wing.
After inspection/consultation- I moved the leading edge of my vert. stab on my RV7 1/4" to the right (heavy left wing) which 'in theory' placed it on the centerline (there is a 1/4" joggle built in). We re-attached the fairing with 4 screws temporarily (some work required to re-do that fairing permanently, didn't want to screw it up if it didn't have any effect).
We took a test flight and got her up to cruise and the ball was centered and almost ALL the heavy wing was removed. To the point that, some Aileron alignment and subtle tweaking can fix the rest of the issue.
My theory- there's a LOT of variables on the plane.
Could there be 1/4" twist in the fuse over the entire lentgh, creating an inability to measure a true centerline without significantly affecting quality- sure.
Could the specific prop and engine combo affect the amount of P force and contribute- sure
In summary, if you have a heavy wing- in level flight check the ball. If you are flying level (counteracting the heavy wing) and it's like walking around with a 10lb weight outstretched and the ball is out, A significant culprit may lie in the vertical stabilizer leading edge.
It took less than an hour to get the fairing off, move the leading edge, install some temporary bolts (similar to the permanent bolts specified) and temporarily re-install (not beautiful but on) the fairing for a test flight.
A permanent fix is to make a new doubler plate that is riveted to the fore support and bolted to the horizontal stab. Use the same holes in the horizontal stab angles and use the same holes in the vertical stab (back drilling). You're left with a few extra AN-3 lightening holes in the flat stock of the fore spar of the horizontal stab (don't temporary drill through angle stock- it's structural).