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Weight increase resulting in a stall speed increase

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Aerodynamics

As weight of the airplane increases the stall speed does increase. Due to the greater weight, a higher angle of attack must be maintained to produce the additional lift to support additional weight in flight.Therefore the critical angle of attack will be reached at a higher airspeed when loaded to maximum gross weight than when flying solo with no baggage. Please could somebody explain the airspeed part in this explanation by the FAA?

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2 Answers



  1. John D Collins on Jun 30, 2014

    If you remember your high school algebra, you can follow along with this explanation of how the stall speed is affected by weight.

    The basic lift formula is stated as L = 1/2 pV^2 x S x CL. The term p is the air density, V is the airspeed, S is the surface area of the wing and CL is the coefficient of lift. Since Lift equals Weight in un-accelerated flight, we can substitute W (Weight) for L (Lift), so W = 1/2 pV^2 x S x CL. We can use W1 for weight one, and W2 for weight two and then V1 will be the airspeed associated with W1 and V2 will be the airspeed associated with W2.

    The wing stalls at a constant angle of attack and at the point where CL is a maximum. This means that the CL at a stall is the same regardless of weight. So we can write the ratio of the weights equal to the following: W2/W1 = (1/2 pV2^2 x S x CL)/(1/2 pV1^2 x S x CL). Since the CL is the same anytime the angle of attack is the same, S is a constant, and p is the same, this can be simplified to the following: W2/W1 = (V2/V1)^2. Take the square root of both sides and then solve for V2 = SQ RT (W2/W1) x V1.

    This works for adjusting the stall speed as a function of weight and for any other speed that has a constant angle of attack. Best glide speed has a constant angle of attack, so it works for adjusting it as well.

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  2. james henley on Feb 06, 2015

    I have always wanted to build a small wind tunnel at home to float on air even if it’s only a little. I can’t figure out how much cubic feet of air flow is needed to keep my 215 lb body in air. Can you break it down for me how to figure that out in lamens terms

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