Winglets, raked (scimitar) winglets, blended winglets, etc. are all about increasing the efficiency of the wing generating lift. On conventional wings there is a circulation of air from the bottom of the wing (higher pressure) around the wingtip to the top of the wing (lower pressure). This...
The short answer is that turboprops (using a turbine engine to turn the propellor) and turbofans (turbojets with a large forward fan section that pushes unheated air around the turbine for additional thrust) are efficient.
At lower speeds (Mach <= 0.5) and for use on smaller aircraft (C-130)...
Talking with an F-22 test pilot from Edwards gave me a lil insight into how the Raptor is able to attain supersonic speeds without the use of an afterburner. The F-22 initially climbs to an altitude between 40000 and 45000 feet. At this altitude the air is less dense, which produces less drag...