I have never flown the MD-11 but have flown numerous FMS aircraft none of which could you program a step climb. Although the computer knows your current weight, altitude, temperature and winds it cannot accurately predict these factors as you climb. In a climb, it is restricted to thrust and airspeed limits. In a descent, you can vary thrust (idle to max), airspeed (within limits) and use the always handy speedbrakes to make an altitude restriction. Hope that answers your question