Testing a Model with extra Vector Fermions at the LEP2 Collider

Our aim is to test a model recently presented, motivated by the reported $R_b$ and $R_c$ ``crisis", which contains extra vector fermions. We suggest an alternative indirect test of the possible existence of new heavy quark flavours at the LEP2 collider, which turns out to give the clearest signal. We calculate $q\bar{q}$ cross sections within this framework, including one loop corrections, and find measurable differences compared to the Standard Model predictions.