FAA Flight Instructor Airplane (FIA)Aerodynamics and Principles of FlightEasy
A technician installs winglets (small, nearly vertical extensions) on the wingtips of a light twin to improve cruise efficiency. Aerodynamically, how do winglets primarily improve performance?
- AThey reduce induced drag by weakening the wingtip vortices, effectively acting like an increase in aspect ratio
- BThey increase dihedral effect by adding vertical surface area at the tip
- CThey increase the strength of the wingtip vortices to improve roll control
- DThey increase parasite drag intentionally to slow the airplane for approach
Show answer & explanationAnswer & explanation
Correct answer: A. They reduce induced drag by weakening the wingtip vortices, effectively acting like an increase in aspect ratio
Winglets interrupt the spanwise flow that feeds the wingtip vortex, reducing the strength of the vortex and the resulting induced drag. This has an aerodynamic effect similar to increasing wingspan/aspect ratio without the structural penalty of a longer wing, improving cruise efficiency.
Why the other options are wrong
- B. Winglets are not primarily installed to increase dihedral effect or lateral stability.
- C. Increasing vortex strength would increase induced drag, the opposite of the intended effect.
- D. Winglets are designed to reduce drag for efficiency, not to intentionally add drag.
Winglets
Vertical or near-vertical extensions at the wingtip that reduce the strength of wingtip vortices, lowering induced drag and improving fuel efficiency.
- Reduce induced drag by weakening wingtip vortices
- Aerodynamically similar to increasing wingspan/aspect ratio
- Most beneficial in cruise where induced drag is a larger share of total drag
Memory trick: Winglets whittle away the whirl at the wingtip.