In [1-5] it was found that a flow pa ra l l e l to the burning sur face of a propel lan t changes i t s l inear bu rn ing r a t e . TMs effect i s usual ly cal led e ros ive burning. The burning r a t e may r i s e or fal l (positive and negat ive eros ion, r e spec t ive ly ) . Pos i t ive e ros ion has a we l l es tab l i shed phys ica l explanation: the higher burning r a t e is a t t r ibutable to an i n c r e a s e in the effect ive t h e r m a l conductivity and diffusion coeff ic ients in the developed s m a l l s c a l e turbulent p roduc t flow (Damkb~le r -Shehe lk in effect) . With r e g a r d to negat ive e ros ion it is poss ib le to advance two hypotheses .