Numerical simulations have been performed to examine the interference effects between an upstream flapping airfoil and a downstream stationary airfoil in a tandem configuration at a Reynolds number of 1000, which is around the regime of small flapping micro aerial vehicles. The objective is to investigate the effect of the distance of the tail and its angle of attack on the overall propulsive efficiency, thrust and lift. An immersed boundary method Navier-Stokes solver is used for the simulation. Results show that efficiency and average thrust can be increased up to 10% and 25% respectively when a stationary airfoil is placed downstream. The simulations reveal how the vortex-shedding pattern of the airfoils are affected by the interaction between them. As the angle of attack of this airfoil increases from 0 to 45o, high lift is generated at the expense of rapidly decreasing efficiency and thrust. The results are not very sensitive to the shape of the airfoil; similar results are obtained with a flat plate airfoil. Lastly, a simple optimization study is performed to obtain the configuration which gave the best performance based on the range of parameters studied. The results obtained from this study can be used to optimize the performance of small flapping MAVs.