Bestimmungen für Flugmodelle:

Only powered flight and sail flight models up to a maximum take-off weight by 25 kg may be operated.
Models over 25 kg need a special permission, which can be given by the air supervisory authority and by the DMFV (Deutscher ModellFlugVerband - German model flight association).

Only three flight models with combustion engines should be operated at the same time.
Turbine-driven flight models may only fly alone.

Models with combustion engines are only allowed up to 71 dB(A)/25 m at full throttle.
This value applies to control line models, which are in accordance with BeMod 2007 of the FAI for control line models, too.
Turbine-driven flight models are only allowed up to 84 dB(A) / 25 m at full throttle.

You are only allowed to use planes with combustion engines, if it is recorded in your noise pass ("Lärmpass").