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tip vortices, flaps and induced drag

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  • tip vortices, flaps and induced drag


    Question 810215 states that If flaps are deployed at constant IAS in straight and level flight, the magnitude of tip vortices will eventually decrease

    Question 810220 states that Induced drag is the result of downwash generated by tip vortices.

    Question 810221 states that extending the flaps will not reduce induced drag.

    i am a bit confused about those questions...

  • #2
    Flaps may decrease the vorticese at the tip, but they create additional voriticese at the outboard ends of the flaps.

    https://www.youtube.com/watch?v=wg5ZaWvRdHE

    Designers try to minimise induced drag by designing the wing to have a span wise lift distribution which is close to the optimal (elliptical) shape. Flaps tend to produce a sub optimal span wise lift distribution.

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    • #3
      Aerodynamics is a complex science. Exam questions, of necessity, are extremely brief. You cannot expect the whole story of a topic to be told in a 5 word answer.
      So

      QID 810215: The question specifically asks about TIP vortices, which decrease. A correct statement, but not the whole story. Vortices are created elsewhere, which means that induced drag can remain the same - as stated in 810221.

      QID 810220. Tip vortices DO create induced drag. A correct statement, but not the whole story. Other things create induced drag as well, but none of them are included in the other 3 answers on offer.

      The ability to recognise WRONG answers is an important skill to use in finding the required answer in ATPL exams.

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