During the 1930s, studies showed the need for engines capable of developing one horsepower per cubic inch of displacement (about 45 kW/litre). This power output was needed to propel aircraft large enough to carry large fuel loads, for long range flights. A typical large engine of the era, the Pratt & Whitney R-1830 "Twin Wasp", developed about 1,200 hp (895 kW) from 1,830 cubic inches (30 litres), so an advance of some 50 percent would be needed. This called for radical changes and while many companies tried to build such an engine, none succeeded.