We investigate finite translation
planes of dimension d over the kernel K = GF(q), where q = pk with p a prime,
having a collineation group G with either G =PSL(2,w) or G =SL(3,w), where w is
a prime power. We derive several restrictions on the planes; for example, if p is odd
then 4 divides d. We also give a new characterization of the Lorimer-Rahilly and
Johnson-Walker planes of order 16, which is more general than that of Johnson and
Ostrom. In addition, we give many examples indicating how good are our
results.