Very roughly: unless you are flying IFR to an international airport (i.e. one listed in Jeppesen for Russia; ULLI is one of them), you have to have a Russian navigator in the cockpit, or the PIC must be a Russian citizen. IFR flight plans usually have to be filed 24 hours in advance.
On the other hand, if you just want to fly in a club ATZ, you can most likely get away with it. In fact, you can probably take aerobatics lessons in a Yak-52 much cheaper than in W. Europe. I can put you in contact with the clubs near St. Petersburg if you want.
Last edited by Ultranomad; 15th Apr 2009 at 00:20.