Mystery needs an Ercoupe Guru...

Wow! Thanks for the detailed report!

I really missed the mark when I thought it wasn't an aileron issue, huh? I guess the first step should have been, "with the yoke centered, see if it taxis straight ahead and the ailerons are neutral."

It can be intimidating to hear "not airworthy" from your mechanic but it sounds like all you need is a thorough, proper re-rigging and I bet it'll make a night and day difference. (My coupe restoration had so many "well THAT'S not airworthy" moments that it stopped bothering me too much and I started appreciating the fact that these things can still fly when they're not quite up to snuff, because the former owner has been flying it in that condition anyway)

If you had improper safety wiring in the control system I'm VERY glad you're getting it taken care of. Just in the chain between the two yokes, there are three turnbuckles that need to be wired up right because they control the alignment of the yokes to each other, the yoke alignment to the main control rods, and they hold the chain on!!! That's an absolutely critical safety of flight item. I learned turnbuckle safety wire doing them once, then cutting it off and redoing it to tweak the rigging alignment, and honestly I'll probably do it a third time because my A&P wired my rudder cable turnbuckles and his technique is so much prettier than mine.

Please post again after the rigging job and let me know how it turns out.

Plane finally is in annual.
Despite coming from a self claimed very knowledgeable seller/owner my A&P found a lot of problematic issues with the rigging.
As for the extreme crabbing move right after takeoff we found that nose wheel and ailerons were not aligned. When nose wheel was straight left aileron was up and right was down.
During takeoff roll nose wheel was steering plane straight even with the ailerons were not neutral. But as soon as nose wheel gets off the runway plane is controlled with the ailerons position and naturally sways to the left and ground effect makes the move more extreme for the next 5-10 seconds.

One of the control cables were so tight that exceeded the max allowable tension level and as my A&P described "it felt like a piano string."

All safety wires attached either wrong or some of them were missing where they supposed to be at.
Now, he has the Ercoupe service manuals I provided him and he'll go through and re-rig the whole plane from the beginning.
As in current condition it is not-airworthy he said.
We are still disassembling other parts and pieces. So far engine compression was the only thing came out great and as he said plane was in great shape but the setup was horribly done.
Today and Monday we will go thru wheel bearings, nose wheel, tail height setup, leveling the wings and checking donuts etc...
Fingers crossed!
 

Thank you for the response and the recommendations and especially for you to take time to offer helpful advice. If you were any closer than Maryland I would've fly you here ; )
I have all the Service manuals and documentation that I will provide to the only A&P available in my area. His experience so far is one other Ercoupe he did annual in the past. How long ago it was? No idea! So fingers crossed... waiting that time to come next week.
But I will take a note what you said and check all those items you mentioned. Again, thank you!

James,

I haven't done a lot of flying yet but I just finished up an extensive restoration that included all of my coupe's flight controls. This involved a LOT of discussion with experienced mechanics about what would happen if certain parts failed, or if certain things were out of spec, misadjusted, etc., so take whatever I have to say with a healthy dose of skepticism but I have a few ideas.

This doesn't sound like an aileron problem, and if you had a bent wing I can only imagine that it wouldn't get better after takeoff as you are experiencing. If I were dealing with this, I think I'd go through it in this order. Not necessarily from most likely to least likely... sometimes it's worth checking the stuff that's easier to access first.

1. Visually inspect the rubber engine mount bushings and then engine mount itself to make sure you don't have a misaligned engine, or an engine that's moving out of alignment when thrust is applied.

2. With the nosewheel on the ground (i.e. steering more or less locked straight ahead) wiggle each rudder side to side gently. You're checking for looseness in the rudder cables and rods. The rudder cables in an Ercoupe are supposed to be MUCH tighter than conventional aircraft. Occasionally this gets overlooked and you end up with flutter or adverse yaw issues.

3. Give the rudders a little more forceful push (about 15-20 pounds worth) and make sure there's no flexing or popping. You're checking for internal damage to the rudder that can cause flexing or oil canning, and also damage to the rudder horns.
dyzz9obi78pm5.cloudfront.net/app/image/i...9a/n/ad-59-25-05.pdf

4. Raise the nosewheel off the ground, either by hoisting the engine or by pressing down on the tail. Proper procedures are in the Ercoupe service manual . Have someone turn the yoke fully back and forth and observe rudder movement plus feel for resistance or binding. You're checking for integrity and freedom-of-movement in the rudder bellcrank where the rudder cables transfer motion to the rudder rods.
dyzz9obi78pm5.cloudfront.net/app/image/i...eb/n/ad-67-06-03.pdf

5. Look under the center of the elevator for three inspection ports from Service Bulletin 34 . If they're not present, you should consider purchasing the kit from Univair and having them installed. The elevator control horn (steel) in bolted and riveted to the aluminum skin and aluminum elevator spar. Over time, dissimilar metal corrosion can damage this connection. Installation is easiest if you remove the tail and flip it over on a bench, but this isn't actually very difficult (I've done it twice now) and then it easy to fully inspect everything in the rudder & elevator controls.  I can imagine a failure mode where the horn settles into a new position at the beginning of each flight as aerodynamic forces come into effect. Sooner or later it could separate completely.

6. If everything above checks out, I'd make sure that the A&P has a copy of the Rigging Guide at annual time because Ercoupe empennage rigging is unique.  

C85-12... SMOH 60

This 1946 415-C has a tail section from 1966 Alon A2 with an STC on it.
So I have split elevator.

The "slop" you're referring is one of the the few reasonable explanation we're trying to explain this issue with as a reason. But we're not sure at the moment. Again, the plane will go into the annual on 25th March and we will check everything to figure this out.

P factor alone can't be this extreme as couple other Ercoupe owners/pilots flying this specific plane expressed that they never experienced this extreme head swing and wing drop and scared the crap out of them when it happened.
On a dead calm day, liftoff over the centerline and in 3 seconds you're out of the left side of the runway under you...

If you provide me your email, I'll send you the video to see how extreme it is.
But the head sway to the left and the amount of right wing drop is being consistently the same all the time tells me something wrong with the setup that effects the plane at that moment.
But no idea what it may be at this point!

The only thing I can think off logically "What is being done differently at the moment of takeoff compared to the rest of the flight?"
Answer is : "Applying more back pressure to the yoke!"
The next logical question is: "What is the outside effect airplane endures between 0-25' during the moment of takeoff?"
That answer is the "Ground Effect"...

Since when airplane reaches 30' AGL following this head sway and wing drop, at that point this movement disappears and corrects itself with a little input by the pilot and it never shows this or any type of awkward behavior again until next takeoff moment.. That is the confusing part to everyone so far! Climbs, flies and lands all ok with no issues.