FAA Airline Transport Pilot (ATM)Transport Aerodynamics and High-Altitude OperationsEasy
An airline retrofits its transport fleet with winglets. What is the primary aerodynamic benefit?
- AThey increase parasite drag intentionally to improve high-speed stability
- BThey shift the center of pressure aft to improve longitudinal stability
- CThey increase the aircraft's critical Mach number by delaying shock wave formation over the wing
- DThey reduce the strength of wingtip vortices, effectively increasing aspect ratio and reducing induced drag
Show answer & explanationAnswer & explanation
Correct answer: D. They reduce the strength of wingtip vortices, effectively increasing aspect ratio and reducing induced drag
Winglets redirect the wingtip vortex flow, reducing its strength and the associated induced drag, which behaves as if the wing had a higher aspect ratio without physically extending the span.
Why the other options are wrong
- A. Winglets are designed to reduce drag, not add parasite drag.
- B. Winglets have negligible effect on longitudinal center of pressure location.
- C. Winglets are not primarily a compressibility/Mcrit device; that's addressed by sweep and airfoil design.
Winglets
Vertical or angled wingtip devices that reduce the strength of wingtip vortices, lowering induced drag and improving fuel efficiency.
- Effectively increase aspect ratio without extending span
- Reduce induced drag, improving cruise fuel burn
- Do not significantly affect Mcrit or CG
Memory trick: Winglets cap the swirl like a lid on a jar