We find to be to + infinitive to discuss official arrangements, orders or official instructions.
This structure has both active form and passive form.
We use the passive form when we want to focus on the agent or when we give orders.
The structure of to be to + infinitive in passive voice is:
Subject + to be to + verb [passive form]…
- Everyone who drives without license is to be fined.
- Tents are not to be changed without permission.
- Pilot is to be helped by the cabin crew.
We often use the structure to be to + passive voice in official arrangements:
- if we want to highlighting the agent or doer;
- if we want to give orders.
NOTE: It is not so common to use this structure to give command/order. However teachers and parents mostly use to be to + passive voice when they give order to children.