Not know a whole lot about that airframe I will ask the obvious:

All tire pressures good?

Nose strut pressure good?

What is the CG of the plane with the larger engine, you, but low fuel?

Lastly, takeoff technique of holding the nose down too much?

George



Sent from my iPad

> On May 5, 2014, at 7:17, John Cooper <snopercod@comporium.net> wrote:
>
> This morning I made several fast-taxi runs in my Lanciar 235/O-290-D2. The first few runs were with empty wing tanks and it got real squirrely. The plane would veer from side-to-side with a period of about 3 seconds and it was all I could do to keep it on the runway. I got scared at about 50 KTs, pulled the power, and applied the brakes heavily to keep from going into the weeds. I never could get going fast enough to lift the nose wheel.
>
> I taxied back to the hangar and added 5 gallons of 100LL in each wing tank and repeated the test. The results were much better but the side-to-side oscillation was still there and it was easy to get into a P.I.O.
>
> Is this normal behavior for the small Lancairs? Could this be due to something in the oleo strut? (I don't have the centering mod)...Tire pressure?...Dragging  MLG brake?...Any other ideas?
>
> FWIW, I added a 5" ventral fin and extended the rudder 5" to avoid just this sort of thing with the larger engine. Apparently, those mods don't work at low speeds.
>
> Help!
>
> <Transformed_Lancair Easter weight balance 004.JPG>