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2 Answers

Maneuvering Speed

Asked by: 2181 views Aerodynamics, Flight Instructor

For what aerodynamic reason dose Va increase with weight?

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2 Answers

  1. John D. Collins on Jun 22, 2013

    Va increases with weight because the stall speed increases with weight. The strength of the wing is designed to be able to sustain a certain G loading without any damage. The G loading is the ratio of lift to weight, so for level flight where the airplane is not accelerated, the lift equals the weight. If you accelerate the airplane by a turn or pulling back on the yoke, you generate more lift and the G loading increases since the weight remains constant.

    For an aircraft certified to Normal Category, it must be able to sustain at least 3.8 G’s of load, For Utility category, it must be stronger and be able to sustain at least 4.4 G’s of load. The rest of the aircraft must also be able to not incur damage at the same loading. If one pulls the yoke aft in a rapid motion, the aircraft will accelerate and at some point it will stall. At the point of the accelerated stall, the wings will not produce any more lift and therefore can’t induce any more G loading. The stall speed when the aircraft is undergoing G loading is related to the power off stall speed times the square root of the G loading. This can be determined from the basic lift formulae (I will leave this to you to research). This means that if you remain under the speed equal to the square root of the design G loading times the power off stall speed, the aircraft will stall before exceeding the maximum permitted G loading. At lighter weights, the stall speed is lower, and the divisor of the G load equation is also lower (lift divided by weight). At a given speed (angle of attack) the wings will produce the same amount of lift. But since the weight is lower the result of the division is higher, or more G’s will be produced at the lighter weight,. To keep the G loading below the maximum permitted by the design, you must correspondingly lower the Va value.

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  2. Lucas on Jun 22, 2013

    I actually made a youtube video a while back for another student here is the link:


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