This is a failure of the MCP speed window. Selecting ALT should result in SPD, the speed window was unable to open or send the info, it cannot use VNAV(FMC info) with ALT as the vertical mode.
Selecting VNAV would probably rectify the situation as the data would come from the FMC rather than the MCP.
Last edited by SMOC; 24th January 2015 at 08:51.