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The transonic effect develops...

  • A

    Above MCRIT.

  • B

    Below MCRIT.

  • C

    Above MFS.

  • D

    Above M0.4.

Refer to figure.

Figure shows the flow speed ranges with their approximate Mach number values, where:

  • MFS (Free Stream Mach number) is the Mach number of the flow sufficiently remote from a blade to be unaffected by it.
  • ML (Local Mach number) is the actual speed of the flow over a surface. When a blade flies at a certain MFS the flow over it is accelerated in some places and slowed down in others.
  • The transonic speed region is developed above MCRIT. The blade tips of some high-speed helicopters will be operating in the transonic region. At and above MCRIT a normal shockwave will form over the upper surface of the blade.

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  • Austro Control