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7 Answers

Manuevering Speed

Asked by: 5350 views Light Sport Aircraft

Can you please explaine the differance between Vo "maximum operating maneuvering speed" and Va Design manuevering speed in a Cessna Skycatcher.. Not sure why they are both listed and when asked what would be my rough air penetration speed I presume Vo would be the answer?

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7 Answers

  1. Derek Schwalenberg on Apr 03, 2014

    Vno is the maximum structural cruising speed. It is the beginning of the yellow arc (or caution range) and can be exceeded in smooth air if no abrupt control movements are made. It’s OK but you better be real gentle and it shouldn’t be in turbulent conditions either. Va is the manuevering speed. Below Va the airplane will stall before it breaks. This is why in strong turbulence or when doing maneuvers it is recommended to be below Va. Even the strongest turbulence or jerk of the flight controls will not damage the airframe below this speed. The best way to understand why is look at a ‘Vg Diagram’ http://www.faatest.com/books/FLT/Chapter17/Vg%20Diagram_files/imageTHE.jpg

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  2. Sam Dawson on Apr 04, 2014

    The statement that you can can jerk the flight controls below Va and damage to the airframe will not occur is false. The correct statement is:

    “The design maneuvering speed (VA) is the speed below which you can move a single flight control, one time, to its full deflection, for one axis of airplane rotation only (pitch, roll or yaw), in smooth air, without risk of damage to the airplane.”



    Also remember that Va goes down with weight- most operating handbooks only supply a Va number based upon maximum gross weight and this should be reduced for lower weights. STC items such as vortex generators may also affect Va. Vortex generators reduce your stall speed, which in turn reduces Va.

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  3. IMSee on Apr 04, 2014

    I’m not sure of the correct answer, but I can see the previous two replies either misread or misinterpreted your question. Here are the applicable regs as a starting point:

    FAR 23.335: (c) Design maneuvering speed VA.
    For VA, the following applies:
    (1) VA may not be less than VS√n where—
    (i) VS is a computed stalling speed with flaps retracted at the design weight, normally based on the maximum airplane normal force coefficients, CNA; and
    (ii) n is the limit maneuvering load factor used in design
    (2) The value of VA need not exceed the value of VC used in design.

    FAR 23.1507: The maximum operating maneuvering speed, VO, must be established as an operating limitation. VO is a selected speed that is not greater than VS√n established in §23.335(c).

    Maybe somebody can take it from here?

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  4. Sam Dawson on Apr 04, 2014

    I did not misinterpret the question I was just clarifying a misconception given in the previous answer.

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  5. Brian on Apr 05, 2014

    Sam, say what you said again, but replace Va with Vo. The regulation does not require Va to be equal to, or less than, Vs * Sqrt (n). (Or stall times sqrt load factor) In other words, Va could potentially result in failure even if just one control surface is pulled to it’s maximum IF that published Va is greater than Vs * sqrt (n).

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  6. Sam Dawson on Apr 07, 2014

    I don’t believe the Skycatcher is a normal, utility, aerobatic or commuter airplane. As such any references to FAR 23 with the Skycatcher are not correct. It is a light sport or primary airplane and as such FAR 23 does not apply.

    Second, my statement about Va is taken directly from the FAA, not something I made up. So it is correct as written. Please read my references.

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  7. Brian on Apr 15, 2014

    “Second, my statement about Va is taken directly from the FAA, not something I made up.”

    And the FAA has never been out dated or just plain wrong about anything dynamically related to airplanes?

    Find something for me in 8130.2 that specifies this speed for light sport aircraft. To my knowledge, which I’m not well read on light sport, there is no such mention of Vo. However, Vo is a new addition to part 23 and I suspect its mention here parallels this change. Vo is what Va is described to be.

    Maneuvering speed = sqrt (load factor) multiplied by stall speed. The part 23 Va requirements did not have to meet this value and, therefore, did not necessarily mean you were safe in the manner described in your FAA citation. It is for this reason Vo was made a requirement in part 23. Again, I’m not certain what this means for light sport aircraft.

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