It is considered good practice by the Agency to anticipate temporary absence of the key managers (Head of Design Organisation, Head of Office of Airworthiness and Head of Independent System Monitoring), but usually the Agency will not require an EASA DOA Form 4 for any deputy function.
It is expected that the deputy function is established to ensure continuity in the execution of tasks – in absence of the main post holder - while the responsibilities remain with the nominated manager. This delegation of tasks is feasible whilst properly described in the Design Organisation Handbook.
An exemption should be considered the case when the key manager will be absent for a long time (e.g. maternity leave or extensive sick leave) and cannot be realistically expected to assume responsibility during his/her absence, but is expected to return to his/her nominated function (and thus remaining in the key management position within the company). In this case, a deputy should be nominated to cover the period of absence. This should be considered a significant change to the Design Assurance System (covered by an EASA Form 82), and the nomination of the deputy functionary should be made including EASA DOA Form 4.