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Thrust in Newtons (aviation)

  1. Nov 7, 2014 #1
    Given that an engine's rated power is 160 HP (~119kW), how can I express thrust (T) in newtons, if aerodynamic drag (D) requires weight expressed in newtons as well to ensure consistency when calculating power available (Pa) and power required (Pr)?:

    [itex]D = (\frac{1}{2}\rho SC_{D})V^{2}+\frac{2W^2}{\rho S\pi AV^2}[/itex]


    [itex]\rho[/itex] = density at given altitude, [itex]\frac{kg}{m^3}[/itex]
    [itex]S[/itex] = wing area, [itex]m^2[/itex]
    [itex]C_{D}[/itex] = zero-lift coefficient of drag
    [itex]V[/itex] = true airspeed, [itex]\frac{m}{s}[/itex]
    [itex]A[/itex] = wing aspect ratio

    I want to solve the equation for excess power: [itex]P_{ex} = P_{a} - P_{r} = TV - DV[/itex]

    Thank you!

  2. jcsd
  3. Nov 8, 2014 #2


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    Gold Member

    Power is expressed by the relation
    P = F * V
    P is power,
    F is force (thrust, drag, etc)
    V is velocity (speed)
  4. Nov 10, 2014 #3


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    Rather than changing the thrust to newtons, why don't you convert the drag force to a power required value? You can do that with the equation mentioned by OldEngr63 above - knowing the drag force at any given speed, you can calculate the power required for level flight. Power available won't be the engine power though, which will complicate things - if you want an accurate result, you should also account for propeller efficiency.
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