Medium bomber

A medium bomber is a bomber aircraft designed to operate with medium bombloads over medium distances; primarily to distinguish them from the much larger heavy bombers and smaller light bombers. The term was used primarily prior to and during World War II, when engine power was so scarce that designs had to be carefully tailored to their missions. The medium bomber was generally considered to be any design that delivered about 4,000lbs over ranges of about 1,500-2,000 miles. Heavy bombers were those with a nominal load of 8,000lb or more, and light bombers carried 2,000lb loads. These distinctions were already disappearing by the middle of WWII, when the average fighter aircraft could now carry a 2,000lb load and ever more powerful engines allowed "light" designs had now largely taken over the missions formerly filled by mediums.

After the war the term disappeared from use almost instantly. Although a number of aircraft were designed in this performance range, they were now almost universally referred to as tactical bombers instead. Famous examples of post-war mediums include the English Electric Canberra (as well as it's US counterpart, the Martin B-57) and Ilyushin Il-28 Beagle.

Examples:

Heinkel He 111

- considered a heavy by the Luftwaffe

Junkers Ju 88

B-25 Mitchell

B-26 Marauder

Vickers Wellington

Bristol Beufort

deHavilland Mosquito

- started as a light bomber, but increasing capacity made it one of the world's best mediums by the end of the war