Simple. Level change closes the thrust levers (or opens) and speed is MCP/ FCU speed, VS gives priority to vertical speed, thrust levers adjust accordingly to maintain the VS, not the MCP or FCU speed. On some A/c there is no stall or overspeed protection when in VS mode, (757 example)
Last edited by Kirks gusset; 10th January 2010 at 14:26.