HAWK21MOut here Aircraft with MAUW of 5700kgs & above are called heavy Aircraft,below 5700kgs are light aircraft.
regds
MEL
In the UK none pressurised aircraft above 5700 also fall under the same licence, hence you would get DC3 airframe and as most hold 6.3 with 5.5 and the Catalina etc..... but on the EASA licence they would be added as a type.....you would get all piston engines under 6.3 so would hold the DC4 DC6 DC7 engine wise as well.