Systems Engineering concerns the complete process for the development of complex systems comprising hardware, software, facilities and personnel. Such systems are hybrid, as some components are characterised by continuous behaviour, whereas the behaviour of others is discrete. SysML provides graphical notations capturing requirements for systems engineering. Here we present a concise conceptual model for systems engineering that is capable to capture the gist of SysML. The structural part is based on the common higher-order Entity Relationship model that is extended by continuous functions and various flow constraints. The behavioural part is then formalised by a hybrid extension of Abstract State Machines. The usage of the conceptual model is illustrated by a working example concerning the landing gear equipment of a plane.