As WWII progressed, every opportunity to gain advantage had to be taken. Fighter plane engine capacity was increasing. But that was worthless unless propellers were also modified to turn that extra power into more speed. While the classic 2-blade propeller was known to be the most efficient design, lengthening the blades to utilise the increased power would result in them touching the ground during take-off and landing. One solution was the introduction of the four-blade propeller.